The dynamic characteristics of sandwich composite plates with holes at various locations are investigated
both experimentally and through numerical simulations. The critical parameters which affect the natural
frequencies of such plates with holes or cut-outs are the core and face sheet thicknesses, diameter and
location of the holes and aspect ratio of the plate. A rigorous parametric study has been conducted to
determine their interrelationship and presented in a concise manner. An experimental investigation
has been conducted in the beginning to get an idea about the variations of the above mentioned parameters.
The results can be utilized to determine the changes in dynamic characteristics of sandwich composite
plates with holes with specified diameters and locations. The methodology can also be useful to
control the dynamic responses of such plates by incorporating holes of chosen diameters at appropriate
locations. The results may be used to create design curves for satisfactory dynamic performances of sandwich
composite plate with holes
Gaskets in joints play an important role in the sealing performance of bolted flange joints, and their behavior is
complex due to nonlinear material properties combined with permanent deformation. The variation of contact stresses due to
the pressure of the flange and the material properties of the gasket play important roles in achieving a leak proof joint. In this
paper, a three-dimensional finite element analysis (FEA) of bolted flange joints has been carried out by taking experimentally
obtained loading and unloading characteristics of the gaskets for various thicknesses and loads. Analysis shows that the
distribution of contact stress has a more dominant effect on sealing performance than the limit on flange rotation specified by
ASME.
LABORATORY MODEL TESTS TO EFFECT OF DENSITY TO FILL MATERIAL ON THE PERFORMAN...IAEME Publication
The effective functioning of reinforced earth structures is very much dependent on the quality of materials and construction. Many times, due to poor quality of the materials used and poor quality control measures exercised, the density of the reinforced soil fill is not up to the design requirements, leading to underperformance or distress of the reinforced soil walls. Therefore, it becomes necessary to evaluate the level of underperformance vis-à-vis that of relative compaction. In view of this, in the present study, a series of laboratory experiments were carried out on a model soil wall of 300 mm high with vertical face, prepared at different density states of 95%, 80% and 70% of MDD of IS HCT. The wall was subjected to monotonic load applied through a model square footing of size (B) equal to 50 mm on the surface at an offset distance of 1(B). Similar tests were carried out on the soil wall reinforced with a Woven Geotextile in wrap around form; to study the effect of density on the performance of reinforced soil wall. The results indicated proportionality between relative compaction level and performance of soil wall without and with reinforcement.
STUDY OF STRENGTH PROPERTIES OF POLYESTER FIBRE REINFORCED CONCRETEJournal For Research
Fiber Reinforced Concrete" is relatively a new construction material developed through extensive research and development work during the last two decades. Fiber Reinforced Concrete (FRC) is defined as composite material which consists of conventional concrete reinforced by randomly dispersed short length fibers of specific geometry, made of steel, synthetic (polymeric) or natural fibers. Plain cement concrete has very low tensile strength and causes formation of micro cracks in stressed and unstressed states of concrete. Also, it has a low strain at fracture and brittleness with less ductility especially in case of High Performance Concrete. Fiber Reinforced Concrete is the answer to modify these properties of Plain Concrete. The recent development of Secondary reinforcement in Concrete in various fields has provided a strong technical base for improving the quality of the material. To overcome the deficiencies fibers are used as secondary reinforcement. FRC is Portland cement concrete reinforced with more or less randomly distributed fibers. The choice of fibers varies from synthetic organic materials such as polypropylene or carbon, synthetic inorganic such as steel or polyster, natural organic such as cellulose or sisal to natural inorganic asbestos. The interaction between the fiber and concrete matrix is the fundamental property that affects the performance of a cement based fiber composite materials. An understanding of this interaction is needed for forecasting the fiber contribution and for predicting the behavior of such composites. In present investigation concrete with addition of polyester fiber Recron 3s at various at dosages of 0.25%, 0.50%, 0.75% and 1.00% by weight of cement in the mix design is studied to find the optimum dosage of Polyster fiber for concrete.
International Journal of Engineering Research and Development is an international premier peer reviewed open access engineering and technology journal promoting the discovery, innovation, advancement and dissemination of basic and transitional knowledge in engineering, technology and related disciplines.
We follow "Rigorous Publication" model - means that all articles appear on IJERD after full appraisal, effectiveness, legitimacy and reliability of research content. International Journal of Engineering Research and Development publishes papers online as well as provide hard copy of Journal to authors after publication of paper. It is intended to serve as a forum for researchers, practitioners and developers to exchange ideas and results for the advancement of Engineering & Technology.
The Comparison of Properties of Tinplates during Uniaxial and Biaxial Stresstheijes
The majority of thin steel sheets is used to make of food covers, cans, capsules and other products, which are produced by metal forming. Concerning considerable changes in production of tinplates and still higher requests on their properties there is requirement to use such methods on their evaluation, which are able to determine especially mechanical and plastic properties of sheets quickly and with the low costs. Following of present know-how there were developed new testing methods, which correspond more to steel sheets stress during technological treatment (concerning their stress-strain state). In the contribution we deal with the comparison of properties of tinplates during uniaxial tensile test and biaxial tensile test.
Gaskets in joints play an important role in the sealing performance of bolted flange joints, and their behavior is
complex due to nonlinear material properties combined with permanent deformation. The variation of contact stresses due to
the pressure of the flange and the material properties of the gasket play important roles in achieving a leak proof joint. In this
paper, a three-dimensional finite element analysis (FEA) of bolted flange joints has been carried out by taking experimentally
obtained loading and unloading characteristics of the gaskets for various thicknesses and loads. Analysis shows that the
distribution of contact stress has a more dominant effect on sealing performance than the limit on flange rotation specified by
ASME.
LABORATORY MODEL TESTS TO EFFECT OF DENSITY TO FILL MATERIAL ON THE PERFORMAN...IAEME Publication
The effective functioning of reinforced earth structures is very much dependent on the quality of materials and construction. Many times, due to poor quality of the materials used and poor quality control measures exercised, the density of the reinforced soil fill is not up to the design requirements, leading to underperformance or distress of the reinforced soil walls. Therefore, it becomes necessary to evaluate the level of underperformance vis-à-vis that of relative compaction. In view of this, in the present study, a series of laboratory experiments were carried out on a model soil wall of 300 mm high with vertical face, prepared at different density states of 95%, 80% and 70% of MDD of IS HCT. The wall was subjected to monotonic load applied through a model square footing of size (B) equal to 50 mm on the surface at an offset distance of 1(B). Similar tests were carried out on the soil wall reinforced with a Woven Geotextile in wrap around form; to study the effect of density on the performance of reinforced soil wall. The results indicated proportionality between relative compaction level and performance of soil wall without and with reinforcement.
STUDY OF STRENGTH PROPERTIES OF POLYESTER FIBRE REINFORCED CONCRETEJournal For Research
Fiber Reinforced Concrete" is relatively a new construction material developed through extensive research and development work during the last two decades. Fiber Reinforced Concrete (FRC) is defined as composite material which consists of conventional concrete reinforced by randomly dispersed short length fibers of specific geometry, made of steel, synthetic (polymeric) or natural fibers. Plain cement concrete has very low tensile strength and causes formation of micro cracks in stressed and unstressed states of concrete. Also, it has a low strain at fracture and brittleness with less ductility especially in case of High Performance Concrete. Fiber Reinforced Concrete is the answer to modify these properties of Plain Concrete. The recent development of Secondary reinforcement in Concrete in various fields has provided a strong technical base for improving the quality of the material. To overcome the deficiencies fibers are used as secondary reinforcement. FRC is Portland cement concrete reinforced with more or less randomly distributed fibers. The choice of fibers varies from synthetic organic materials such as polypropylene or carbon, synthetic inorganic such as steel or polyster, natural organic such as cellulose or sisal to natural inorganic asbestos. The interaction between the fiber and concrete matrix is the fundamental property that affects the performance of a cement based fiber composite materials. An understanding of this interaction is needed for forecasting the fiber contribution and for predicting the behavior of such composites. In present investigation concrete with addition of polyester fiber Recron 3s at various at dosages of 0.25%, 0.50%, 0.75% and 1.00% by weight of cement in the mix design is studied to find the optimum dosage of Polyster fiber for concrete.
International Journal of Engineering Research and Development is an international premier peer reviewed open access engineering and technology journal promoting the discovery, innovation, advancement and dissemination of basic and transitional knowledge in engineering, technology and related disciplines.
We follow "Rigorous Publication" model - means that all articles appear on IJERD after full appraisal, effectiveness, legitimacy and reliability of research content. International Journal of Engineering Research and Development publishes papers online as well as provide hard copy of Journal to authors after publication of paper. It is intended to serve as a forum for researchers, practitioners and developers to exchange ideas and results for the advancement of Engineering & Technology.
The Comparison of Properties of Tinplates during Uniaxial and Biaxial Stresstheijes
The majority of thin steel sheets is used to make of food covers, cans, capsules and other products, which are produced by metal forming. Concerning considerable changes in production of tinplates and still higher requests on their properties there is requirement to use such methods on their evaluation, which are able to determine especially mechanical and plastic properties of sheets quickly and with the low costs. Following of present know-how there were developed new testing methods, which correspond more to steel sheets stress during technological treatment (concerning their stress-strain state). In the contribution we deal with the comparison of properties of tinplates during uniaxial tensile test and biaxial tensile test.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
6.a review on wear behaviour of clutch plate made of peek composite materialEditorJST
The conventional clutch plate made of carbon fiber and ceramic mixture of copper, iron, tin bronze,
silicon dioxide, and/or graphite, typical alloy is a lamellar pearlitic gray iron like G11H20b of which, it can be
replaced by developing of new materials for reducing the wear rate of the clutch plate the materials chosen is
Poly Ether Ether Ketone (PEEK) based composites mixed with silicon carbide powder shows better results in
which it can be manufactured by the injection moulding process and it is tested in Friction and wear experiment
wear run under constant temperature in a pin-on-disc arrangement, PEEK and its composites used in this
investigated the friction coefficient decreases with the increasing load on PEEK. The composite showed a very
low friction coefficient and wear rate increase in the normal applied load sliding distance decreases wear rate.
Further the wear and friction behaviour decreases with increases the gradually by addition of fillers.
Investigation on fine aggregate by broken tiles in concreteIJARIIT
This examination manages the effect on the concrete by the partial replacement of fine aggregate by ceramic
aggregate. Studies were done on a concrete, with various replacement. The impacts of various replacements 0, 10, 20, 30&40
percent of the waste ceramic tile by weight of concrete with M-30 review. At last, it was reasoned that all the strength qualities
(compressive strength, flexural strength & split tensile strength) of concrete increases with the various replacements.
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Strength of Concrete Containing Basalt FibreIJERA Editor
This paper presents the comparative study of effect of basalt fibre on compressive and split tensile strength of M40 grade concrete. The basalt fibre was mixed in concrete by (0.5%, 1%, and 1.5%) of its total weight of cement in concrete. Results indicated that the strength increases with increase of basalt fibre content up to 1.0% beyond that there is a reduction in strength on increasing basalt fibre. The results show that the concrete specimen with 1.0% of basalt fibre gives better performance when it compared with 0.5%and 1.5% basalt fibre mix in concrete specimens.
Experimental studies on fiber reinforced concreteIJERA Editor
The concepts of using fibres in order to reinforce matrices weak in tension is more than 4500 years old.since Portland cement concrete started to be used widely as a construction material attempts were made to use fibres for arresting cracks enhance the strength etc. The development of fibre reinforcement for concrete was very slow before 1960’s. Fibers are generally used as resistance of cracking and strengthening of concrete. In this project we are going to compare the compressive strength of 3, 7 and 28 days of aramid fibres to the ordinary concrete and fibre reinforced concrete i.e. glass fibres and steel fibres. The concrete is design for M20 grade of concrete. According to various research papers, it has been found that steel fibers give the maximum strength in comparison and glass fibre is used for crack resistance but aramid simultaneously gives strength and can be used for crack resistance. Now a days there exists many reinforcement techniques for improving the strength of those materials which lacks load carrying and less durable capacity. Fiber reinforced concrete has been successfully used in slabs on grade, shotcrete, architectural panels, precast products, offshore structures, structures in seismic regions, thin and thick repairs, crash barriers, footings, hydraulic structures and many other applications. This review study is a trial of giving some highlights for inclusion of aramid fibers especially in terms of using them with new types of concrete
Experimental Evaluation of effect of filler on tensile behaviour of E-glass/e...IJRES Journal
The present work describes the processing and tensile characterization of polymer matrix composites (PMC). Two types of E-glass laminates namely woven and chopped are used as a reinforcing materials and epoxy resin constitutes matrix system. Several works has been carried out to prove that strength of glass fibre composites progressively increased with adding fillers. Keeping this in mind the present work successeded in using wollastonite as a filler material, tensile test samples from both woven and chopped type were prepared and tests are conducted as per ASTM standards and corresponding results are tabulated and discussed. The present work also highlights the tensile strength for both woven and chopped laminates were compared. It is observed that use of wollastonite filler influences greatly on tensile properties of polymer matrix composites. And it is also cleared that woven laminates shows higher resistance to tensile loading as compared to chopped laminates.
DEFORMATIONAL BEHAVIOR OF THE FLAT SLIDING LAYER OF THE SPHERICAL BEARINGIAEME Publication
Analysis of the friction properties of modified PTFE is performed, the functions
describing the change in the friction coefficient depending on the pressure level with a
maximum error from the experiments results less than 1% are proposed in the work.
The influence of friction on the deformation behavior of the flat sliding layer of the
spherical bearing on a periodicity cell model is considered. The geometrical
configuration of the flat sliding layer with truncated spherical hole for the lubricant is
considered. The periodicity cell includes one hole for lubrication. A series of
numerical experiments for three options for the thickness of the sliding layer from 4 to
8 mm with a recess for the lubricant, in the unfavorable case the absence of lubricant
is performed. The pattern of geometric configuration hole change with increasing
pressure level is established. It was found that an increase of the antifriction layer
thickness leads to a less significant deformation of the sliding layer thickness and the
spherical hole. The sliding layer with a thickness of 8 mm has the smallest level
minimum stress intensity and the material volume with the maximum stress intensity is
minimal for this variant of the sliding layer thickness compared to other variants. The
maximum integral stiffness of the 8 mm sliding layer decreased slightly by 1.74 and
1.5% on contact without and with lubricant respectively.
Behaviour of interfaces between carbon fibre reinforced polymer and gravel soilseSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Experimental study of behaviour of poultry feather fiber a reinforcing mate...eSAT Journals
Abstract Currently, the abundant quantity of chicken feather produced annually by the poultry industry as a waste in worldwide, is a serious solid agricultural waste problem. The traditional disposal strategies of chicken feather were not environmental friendly. Exploitation of secondary application alone is not a solution to the problem of environmental; also it enhances the commercial value of feathers. In this study, a review on the behaviour of the chicken feather fibers was made to understand their usability as a reinforcing material for composite fabrication. Fibers of some critical length were estimated experimentally and calculated relative density. Tensile property of fiber, dimensional and strength of the quill was estimated. It was observed that, the quill diameters were varying with length, and all of them were not weighing same. Chemical resistivity and burning tests were conducted, and results were reported. Morphology of the nonwoven mats was studied.
Finite Elements Modeling and Analysis of Double Skin Composite PlatesIOSR Journals
Abstract: Double skin composite (DSC) is a form of “steel/concrete/steel” sandwich structure; the steel plates
are connected to a sandwiched concrete core with welded stud shear connectors. In the present paper, a finite
element model for Double Skin Composite (DSC) panels subjected to quasi-static loading is developed. A series
of quasi-static finite elements models are used to analyze deformation and energy absorption capacity of such
system, when perforated by rigid penetrator with conical nose shape. Pilot test model is used to investigate the
failure pattern in the composite panel. The obtained results are compared to the experimental results; good
agreements are obtained between finite element and previous experimental results. Results show that such
elements have great ability of absorbing energy when subjected to perforation due to ductility of lower plate
skin and vertical stiffness of lower shear studs.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
6.a review on wear behaviour of clutch plate made of peek composite materialEditorJST
The conventional clutch plate made of carbon fiber and ceramic mixture of copper, iron, tin bronze,
silicon dioxide, and/or graphite, typical alloy is a lamellar pearlitic gray iron like G11H20b of which, it can be
replaced by developing of new materials for reducing the wear rate of the clutch plate the materials chosen is
Poly Ether Ether Ketone (PEEK) based composites mixed with silicon carbide powder shows better results in
which it can be manufactured by the injection moulding process and it is tested in Friction and wear experiment
wear run under constant temperature in a pin-on-disc arrangement, PEEK and its composites used in this
investigated the friction coefficient decreases with the increasing load on PEEK. The composite showed a very
low friction coefficient and wear rate increase in the normal applied load sliding distance decreases wear rate.
Further the wear and friction behaviour decreases with increases the gradually by addition of fillers.
Investigation on fine aggregate by broken tiles in concreteIJARIIT
This examination manages the effect on the concrete by the partial replacement of fine aggregate by ceramic
aggregate. Studies were done on a concrete, with various replacement. The impacts of various replacements 0, 10, 20, 30&40
percent of the waste ceramic tile by weight of concrete with M-30 review. At last, it was reasoned that all the strength qualities
(compressive strength, flexural strength & split tensile strength) of concrete increases with the various replacements.
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Strength of Concrete Containing Basalt FibreIJERA Editor
This paper presents the comparative study of effect of basalt fibre on compressive and split tensile strength of M40 grade concrete. The basalt fibre was mixed in concrete by (0.5%, 1%, and 1.5%) of its total weight of cement in concrete. Results indicated that the strength increases with increase of basalt fibre content up to 1.0% beyond that there is a reduction in strength on increasing basalt fibre. The results show that the concrete specimen with 1.0% of basalt fibre gives better performance when it compared with 0.5%and 1.5% basalt fibre mix in concrete specimens.
Experimental studies on fiber reinforced concreteIJERA Editor
The concepts of using fibres in order to reinforce matrices weak in tension is more than 4500 years old.since Portland cement concrete started to be used widely as a construction material attempts were made to use fibres for arresting cracks enhance the strength etc. The development of fibre reinforcement for concrete was very slow before 1960’s. Fibers are generally used as resistance of cracking and strengthening of concrete. In this project we are going to compare the compressive strength of 3, 7 and 28 days of aramid fibres to the ordinary concrete and fibre reinforced concrete i.e. glass fibres and steel fibres. The concrete is design for M20 grade of concrete. According to various research papers, it has been found that steel fibers give the maximum strength in comparison and glass fibre is used for crack resistance but aramid simultaneously gives strength and can be used for crack resistance. Now a days there exists many reinforcement techniques for improving the strength of those materials which lacks load carrying and less durable capacity. Fiber reinforced concrete has been successfully used in slabs on grade, shotcrete, architectural panels, precast products, offshore structures, structures in seismic regions, thin and thick repairs, crash barriers, footings, hydraulic structures and many other applications. This review study is a trial of giving some highlights for inclusion of aramid fibers especially in terms of using them with new types of concrete
Experimental Evaluation of effect of filler on tensile behaviour of E-glass/e...IJRES Journal
The present work describes the processing and tensile characterization of polymer matrix composites (PMC). Two types of E-glass laminates namely woven and chopped are used as a reinforcing materials and epoxy resin constitutes matrix system. Several works has been carried out to prove that strength of glass fibre composites progressively increased with adding fillers. Keeping this in mind the present work successeded in using wollastonite as a filler material, tensile test samples from both woven and chopped type were prepared and tests are conducted as per ASTM standards and corresponding results are tabulated and discussed. The present work also highlights the tensile strength for both woven and chopped laminates were compared. It is observed that use of wollastonite filler influences greatly on tensile properties of polymer matrix composites. And it is also cleared that woven laminates shows higher resistance to tensile loading as compared to chopped laminates.
DEFORMATIONAL BEHAVIOR OF THE FLAT SLIDING LAYER OF THE SPHERICAL BEARINGIAEME Publication
Analysis of the friction properties of modified PTFE is performed, the functions
describing the change in the friction coefficient depending on the pressure level with a
maximum error from the experiments results less than 1% are proposed in the work.
The influence of friction on the deformation behavior of the flat sliding layer of the
spherical bearing on a periodicity cell model is considered. The geometrical
configuration of the flat sliding layer with truncated spherical hole for the lubricant is
considered. The periodicity cell includes one hole for lubrication. A series of
numerical experiments for three options for the thickness of the sliding layer from 4 to
8 mm with a recess for the lubricant, in the unfavorable case the absence of lubricant
is performed. The pattern of geometric configuration hole change with increasing
pressure level is established. It was found that an increase of the antifriction layer
thickness leads to a less significant deformation of the sliding layer thickness and the
spherical hole. The sliding layer with a thickness of 8 mm has the smallest level
minimum stress intensity and the material volume with the maximum stress intensity is
minimal for this variant of the sliding layer thickness compared to other variants. The
maximum integral stiffness of the 8 mm sliding layer decreased slightly by 1.74 and
1.5% on contact without and with lubricant respectively.
Behaviour of interfaces between carbon fibre reinforced polymer and gravel soilseSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Experimental study of behaviour of poultry feather fiber a reinforcing mate...eSAT Journals
Abstract Currently, the abundant quantity of chicken feather produced annually by the poultry industry as a waste in worldwide, is a serious solid agricultural waste problem. The traditional disposal strategies of chicken feather were not environmental friendly. Exploitation of secondary application alone is not a solution to the problem of environmental; also it enhances the commercial value of feathers. In this study, a review on the behaviour of the chicken feather fibers was made to understand their usability as a reinforcing material for composite fabrication. Fibers of some critical length were estimated experimentally and calculated relative density. Tensile property of fiber, dimensional and strength of the quill was estimated. It was observed that, the quill diameters were varying with length, and all of them were not weighing same. Chemical resistivity and burning tests were conducted, and results were reported. Morphology of the nonwoven mats was studied.
Finite Elements Modeling and Analysis of Double Skin Composite PlatesIOSR Journals
Abstract: Double skin composite (DSC) is a form of “steel/concrete/steel” sandwich structure; the steel plates
are connected to a sandwiched concrete core with welded stud shear connectors. In the present paper, a finite
element model for Double Skin Composite (DSC) panels subjected to quasi-static loading is developed. A series
of quasi-static finite elements models are used to analyze deformation and energy absorption capacity of such
system, when perforated by rigid penetrator with conical nose shape. Pilot test model is used to investigate the
failure pattern in the composite panel. The obtained results are compared to the experimental results; good
agreements are obtained between finite element and previous experimental results. Results show that such
elements have great ability of absorbing energy when subjected to perforation due to ductility of lower plate
skin and vertical stiffness of lower shear studs.
Experimental and Analytical Investigation of Drilling of Sandwich Composites:...IOSR Journals
A composite material is made out of a mixture or a combination of two or more distinctly differing
materials which are insoluble in each other and differ in form or chemical composition. The technological and
commercial interest in composite material lies in their superior properties of strength-to-weight, stiffness-toweight,
fatigue and thermal expansion compared to metals. Extensive use of composite in application such as
rockets, satellites, missiles, light combat aircraft, advanced light helicopter and trainer air craft has shown that
India is on par with the advanced countries in the development and use of composites in this area.
Drilling is probably the most important conventional mechanical process and it is the most widely used
machining operation. Prediction of cutting forces for any set of cutting parameters is essential in optimal design
and manufacturing of products. It has been predicted that most of the problem associated with hole making
operation, such as drilling, can be attributed to the force generated during cutting operation. Many
developments and experiments are going on drilling of Sandwich composite for damage free drilling along with
the quality of the hole and the effect of tool geometry and tool material.
This paper aims at the comprehensive analytical and experimental investigation work done on the
composites material. The conclusion of the paper discusses the development and outlines the trends for the
research in this field.
Damage tolerance study of honeycomb sandwich structureeSAT Journals
Abstract
Composite materials are essential component in today’s modern world. Structural sandwich construction is one of the first form of composite structures. In this study honeycomb sandwich structure which is a peculiar type of composite structure was investigated for crashworthiness. They are manmade structures with a honeycomb geometry. It consists of three elements ; Top face sheet, Core, Bottom face sheet. They are widely used in aerospace industry, marine, rail, automotive industry, in construction field as prefabricated partition walls, mezzanine floor, doors etc. The main objective of this study was to assess the damage tolerance of honeycomb sandwich structure based on serviceability and safety of the structure ie. to understand ability of structure to sustain defects safely until repair/replacement is performed. Damage tolerance study was performed to know with how much load this structure would safely withstand and also to know till how much load this structure would be made serviceable, if a damage is caused to it. Investigations were performed on both damaged and undamaged specimens by conducting. Four point bending flexure test and Edgewise compression test based on ASTM standards. Also finite element modeling of honeycomb sandwich structure was developed and analysis of the two experiments were performed in Ansys. Ultimate load, tensile and compressive stress values etc. obtained from the two experiments were compared for both damaged and undamaged specimen. Based on the results obtained it could be inferred that the load carrying capacity of honeycomb sandwich structure reduces, if a damage is caused to it but can perform its duty with reduced efficiency.
Natural Fibre Sandwich Composite Panels-Analysis, Testing and CharacterisationIOSR Journals
The paper deals about the development, comparison, testing and analysis of composite materials and
sandwich composite panels. In this paper we have carried out testing of mechanical and physical properties of
coir composites, SMC laminate, Bamboo Composite, Cement bonded wooden particle composite. Then we have
used SMC Laminate on coir composite so as to increase its strength. Also we have carried out tensile test for
bamboo composite, coir composite, cement bonded composite. Then we have compared the values of these
composites. Water absorption test and flame test of coir composite, Bamboo composite has been carried out, so
as to find out the mechanical and physical properties of composite materials. Finally, Bending test and Analysis
of sandwich composite panels has been carried out for bamboo-EPS sandwich panel and Bison-EPS sandwich
panel to understand the characteristics of sandwich composite panels.
STUDY OF MECHANICAL PROPERTIES OF NATURAL FIBRE COMPOSITEIAEME Publication
In the present work an attempt has been made to fabricate a natural fibre reinforced plastic composite using sisal and jute fibres. 20% sisal,10% jute,10% starch,40% epoxy (araldite AY-103) and 20% hardener is used to fabricated
FRP composite. The composite is fabricated by simple hand lay method. Mechanical properties are tested and found satisfactory. Water absorption test of the composite is tested as per ASTM standard. It is observed that material is light in weight with sufficient strength and of low cost which
make it suitable for many engineering applications
Study of properties of banana fiber reinforced compositeseSAT Journals
Abstract Natural fiber composites are nowadays being used in various engineering applications to increase the strength and to optimise the weight and the cost of the product. Various natural fibres such as coir, sisal, jute, coir and banana are used as reinforcement materials. In this paper both treated and untreated banana fiber are taken for the development of the hybrid composite material. The untreated banana fiber is treated by sodium hydroxide to increase the wettability. The untreated banana fiber and sodium hydroxide treated banana fiber are used as reinforcing material for both Epoxy resin matrix and Vinyl ester resin matrix. Coconut shell powder is used along with both untreated and treated banana fiber as a reinforcing material. In this process the banana fiber is treated with 5% of sodium hydroxide for one hour and the specimen is fabricated by hand moulding process. The mould used for fabricating the hybrid composite material is made up of aluminium with a debonding agent applied on the inner side. The banana fiber content is kept constant to 30% of weight fraction of entire composite material. The variation in mechanical properties are studied and analyzed. Here, the tensile strength has calculated by universal testing machine, impact strength has calculated by pendulum impact tester and flexural strength has calculated by universal testing machine with flexural test arrangement of the specimen. Then the treated and untreated specimens are analyzed and compared through Scanning Electron Microscope to study about its adhesion between fiber and resin matrix and surface morphology. Keywords: Natural Fiber Composites, Mechanical Properties, Surface morphology
Geometric modeling: Wire frame, surface and solid modeling - Engineering analysis;
design review and evaluation, automated drafting.
Numerical control: Need - advantages and disadvantages – classifications – Point to
point, straight cut and contouring positioning - incremental and absolute systems – open
loop and closed loop systems – DDA integrator and Interpolators – resolution – CNC and
DNC.
Programmable Logic Controllers (PLC): need – relays - logic ladder program –
timers, simple problems only - Devices in N.C. systems: Driving devices - feed
back devices: encoders, moire fringes, digitizer, resolver, inductosyn, and
tachometer.
A review of Carbon Nanotube Reinforced Aluminium Composite and Functionally ...IJMER
Material selection is a very critical issue when it comes to aerospace engineering. Materials
should have good qualities like light weight, high strength and corrosion resistance with economic
viability. Over the period, Aluminium blends of composite are used for variety of applications. Carbon
Nanotube reinforced Aluminium composites and Functionally graded composites(FGC ) are the new
developments in materials engineering. Gradual but continuous variation in composition and structure
over volume, results in corresponding changes in the properties of material in contrast to homogeneous
mixing of CNT in case of composite. FGM promises to be more suitable in the future. This paper focuses
on brief review of CNT reinforced Aluminium composite and FGM application in aerospace.
Noval Method for Fabrication of 3-D Spacer Fabric Composite and Investigatio...IJMER
The paper deals with the fabrication and flexural property studies of 3D Spacer fabrics with
three different stiffener height, i.e., 5mm, 10mm and 15mm. The specimens were fabricated over two
bidirectional woven fabric surfaces of glass fiber reinforced composite face sheet which were
mechanically connected with vertical threads. An innovative stitching technique was used. The flexural
strength and deflection of fabricated specimens were determined through three point bending test (ASTM
C 393-62). A significant increase in flexural rigidity was observed when it compared with other panels,
and found it is highest for 3D Spacer fabric with stiffener height 3415mm. Also, the results proved that
flexural strength of 3D Spacer fabric increases with respect to the height of the stiffener. Also the results
were compared with simply glued sandwich composite of thickness 15mm and found a significant
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Analysis and Weight Optimization of Split Dish Reactor Using Thermo-Structura...IJERA Editor
A vertical split dish reactor with leg supports is modeled using ansys workbench. Thereafter, external loads, such as self –weight, internal pressure and temperature are applied to the model. Pressure and temperature has been continuously a concern which may lead to structural failure if the resulting stresses are severe and excessive. It is a significant study which requires in-depth investigation to understand the structural characteristics. This paper presents and focuses on some Finite Element (FE) analysis of a split dish reactor will be carried out and maximum stresses in the structure will be determined.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
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Composite cylindrical shells are being used in submarine, underground mines, aerospace applications and other civil engineering applications. Thin cylindrical shells are more prone to fail in buckling rather than material failure. An experimental study on buckling of glass fiber reinforced plastics layered composite cylindrical shells under displacement and load controlled static axial compression are reported The experimental results are compared with general purpose finite element program (ANSYS). Limit point loads evaluated for geometric imperfection magnitudes shows an excellent agreement with experimental results which clearly indicates the confidence gained on the numerical results presented. Present study finds direct application to qualitatively investigate the influence of geometric imperfection on other advanced grid-stiffened structures.
Experimental behavior of circular hsscfrc filled steel tubular columns under ...eSAT Journals
Abstract
This paper presents an outlook on experimental behavior and a comparison with predicted formula on the behaviour of circular
concentrically loaded self-consolidating fibre reinforced concrete filled steel tube columns (HSSCFRC). Forty-five specimens were
tested. The main parameters varied in the tests are: (1) percentage of fiber (2) tube diameter or width to wall thickness ratio (D/t
from 15 to 25) (3) L/d ratio from 2.97 to 7.04 the results from these predictions were compared with the experimental data. The
experimental results) were also validated in this study.
Keywords: Self-compacting concrete; Concrete-filled steel tube; axial load behavior; Ultimate capacity.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Experimental behavior of circular hsscfrc filled steel tubular columns under ...eSAT Journals
Abstract
This paper presents an outlook on experimental behavior and a comparison with predicted formula on the behaviour of circular
concentrically loaded self-consolidating fibre reinforced concrete filled steel tube columns (HSSCFRC). Forty-five specimens were
tested. The main parameters varied in the tests are: (1) percentage of fiber (2) tube diameter or width to wall thickness ratio (D/t
from 15 to 25) (3) L/d ratio from 2.97 to 7.04 the results from these predictions were compared with the experimental data. The
experimental results) were also validated in this study.
Keywords: Self-compacting concrete; Concrete-filled steel tube; axial load behavior; Ultimate capacity.
This research work mainly investigates the local production of 12 built up GFRP I-beams using Hand Lay-Up production method (since up-till now there is no pultrusion industry in Egypt). Overall strength characteristics of these beams will determined experimentally and compared to those manufactured by the Pultrusion process. This comparison will help to estimate to how extent the locally manufactured beams (by Hand Lay-Up technique) can be used in full permanent structures (like pultruded beams) or at least used in light and temporary structures. In order to achieve this goal, the experimental study was divided into two stages: The first stage is to manufacture GFRP plates using glass fibers and polyester. Two types of plates were produced one for flange plates and the other for web plates. These two types of plates are different in fibers orientation of different layers within the plate thickness in order to reach the possible higher tensile and flexural strength for flange plates and possible higher shear strength for web plates. Longitudinal and transverse tensile, compressive, and flexural strength for these two types of plates were experimentally determined using coupons tests. The second stage is to produce built-up GFRP I-beams using the aforementioned plates and composite angles. The overall stiffness and modes of failure of these beams were experimentally determined. The obtained results were compared with those of pultruded I-beams manufactured in the United States by pultrusion process. Also three different connecting methods for the 12 tested beams were investigated, namely: Bonding – Bolting – Bolting/Bonding connecting techniques. Of course it is expected that some local fabrication parameters (like fiber and polymer properties available in the local market, labour, temperature, polymer curing …etc) are expected to affect the properties of the fabricated beams specially that these beams are manufactured manually.
Study of Round Central Hole in Buckling Analysis of Cross Ply LaminatesAM Publications
Laminated structures find many applications in various engineering fields namely aerospace, bio-medical, civil, marine and mechanical engineering due to easy handling, good mechanical properties and low fabrication cost. Laminated plates with round holes and other openings are extensively used as structural members in aircraft design. These holes are act sometimes as access holes, holes for hardware to pass through, or in the case of fuselage, windows and doors or simply used to reduce the weight of the structure. These laminated structures are often subjected to load in one or more direction in cycles or as intermittent load. Thus there is need to study the failure of these components under bi-axial loading with the view to optimize the shape and lay of the components so as they give maximum service and more life. In this paper bi-axial testing machine is developed to determine bucking load of different materials. Experiments are carried out on cross ply composite under various buckling loads on the bi-axial testing machine. The theoretical results, analytical and experimental results are compared with each other. It is observed that the strength of Bakelite composite plates is higher than glass epoxy laminated composite plate. So Bakelite is more suitable than glass epoxy
Experimental and Analytical Investigation of Reinforced Concrete Beams with L...IJAEMSJORNAL
This research presents the experimental and analytical results for reinforced concrete (RC) beams with rectangular large web openings under pure torsion. Fifteen specimens were tested; one solid specimen without opening, six specimens without reinforcement around opening as if an opening is created in an existing beam; where the investigated parameters were opening width, opening height and opening eccentricity from the longitudinal beam axis, and eight specimens with reinforcement installed around the opening to reduce the effect of the opening on the torsional behavior; where the investigated parameters were the shapes and amounts of the reinforcement around the opening. The test results showed that installing stirrups and horizontal reinforcement bars in the chords above and below the openings efficiently increased the cracking and ultimate torque of the tested specimens; where using inclined stirrups by 45º to the longitudinal axis of the specimens increased the ultimate torque to be about 90% of that of the solid specimen. Installing closed stirrups around the opening had small effect on enhancing the torsional behavior of the tested specimen compared with using horizontal and vertical reinforcement bars. The analytical model based on Modified Variable Angle Truss Model (MVATM) used to obtain the torque-rotation curves for beams under pure torsion was modified to incorporate the beams with large web opening which have different arrangements of reinforcement around the opening. MATLAB program language was used to obtain the analytical torque-rotation curves for the tested specimens that have reinforcement around the opening, which were in good agreement with the experimental results.
An Overview of Clearance Optimization in Sheet Metal Blanking ProcessIJMER
Abstract: This document prescribes a model investigation the effect of potential parameters influencing the blanking
process and their interaction. The blanking process optimization carried out by using Design of Experiment (DOE), Finite
Element Method (FEM) with ANSYS Package, Simulation with ABAQUS-Explicit software, Blank soft Software and Neural
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Finite Element Analysis of Composite Deck Slab Using Perfobond Rib as Shear C...IJERA Editor
Nowadays, the composite decks are very common to use in composite or steel construction. In this case of study
the composite slabs have been investigated numerically by Finite Element Method (FEM). Five composite slabs
were analyzed using finite element software LUSAS. The deflection of each model were obtained and compared
with experimental test. Results showed a good agreement with the experimental data and indicate that the
perfobond rib is appropriate shear connector for the bridges decks
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The dynamic performance of any structure is extremely important from the safety, vibration serviceability and its operation point of view. Such behaviour is dependent mainly on the material properties and boundary stiffness parameters. For old infrastructural facilities in exposed environment, such parameters undergo substantial degradation from their initial values and are difficult to be assessed directly in operating conditions. These deteriorated parameters are estimated solving an inverse problem by correlating responses which can be easily measured with the responses obtained using finite element modeling and updating the initially assumed values of the parameters. The objective function, describing the differences in responses between the experimental and numerical models, is minimized iteratively to estimate the material and boundary stiffness parameters. The gradient based optimization methods are preferred due to their faster convergence from a set of initial guess points, but suffers mostly from lack of reliable methodology to select appropriate step sizes. Arbitrary selection of step sizes may sometimes work well, depending upon the judgment of the user, but is case specific. The present work describes the estimation of existing material properties and boundary stiffness of isotropic and orthotropic plates from measured frequencies and mode shapes using a new gradient based step size controlled inverse eigensensitivity algorithm. The method takes a strategy that the step sizes automatically become smaller when the change in gradient of objective function is having a high value and similarly, takes larger steps when the gradient is remaining fairly constants in subsequent iterations. The results obtained from the investigations are encouraging, as some convergences could be achieved by this new adaptive step size control only, whereas methods adopting arbitrary or no step size control diverged.
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Damage detection using vibration response is a vibrant area of research. Usually, measured natural frequencies are compared with the natural frequencies computed using a baseline finite element model and the objective function thus formed from the discrepancies of results are minimized using various algorithms. One such algorithm is the Support Vector Machine (SVM) algorithm which uses simulations of various damage scenarios. Damage is envisaged using stiffness loss in a member and the damaged responses are recorded and later on retrieved for comparison. The algorithm is found to be very robust for single damage cases of beam type of structures.
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curvature is presented here which can identify both the existence of damage as well
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using the present algorithm has been verified.
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Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
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Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
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Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
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• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
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• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
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1. Dynamic performance of sandwich composite plates with circular
hole/cut-out: A mixed experimental–numerical study
S. Mondal, A.K. Patra, S. Chakraborty, N. Mitra ⇑
Department of Civil Engineering, Indian Institute of Technology Kharagpur, India
a r t i c l e i n f o
Article history:
Available online 19 May 2015
Keywords:
Sandwich composite
Plate with cut-out
Modal analysis
Finite element analysis
a b s t r a c t
The dynamic characteristics of sandwich composite plates with holes at various locations are investigated
both experimentally and through numerical simulations. The critical parameters which affect the natural
frequencies of such plates with holes or cut-outs are the core and face sheet thicknesses, diameter and
location of the holes and aspect ratio of the plate. A rigorous parametric study has been conducted to
determine their interrelationship and presented in a concise manner. An experimental investigation
has been conducted in the beginning to get an idea about the variations of the above mentioned param-
eters. The results can be utilized to determine the changes in dynamic characteristics of sandwich com-
posite plates with holes with specified diameters and locations. The methodology can also be useful to
control the dynamic responses of such plates by incorporating holes of chosen diameters at appropriate
locations. The results may be used to create design curves for satisfactory dynamic performances of sand-
wich composite plate with holes.
Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction
Sandwich composite plates are being increasingly utilized as
different components of the marine, aerial and terrestrial struc-
tures. Cut-outs/holes are also a requirement in these structures pri-
marily for the purpose of making the structure lighter, for venting
and inspection, for providing a passage for service facilities like
cables, fuel pipes etc., for fastening/mounting other structural
members and/or instruments using bolts and rivets. It is quite
obvious that the introduction of a hole/cut-out will result in shifts
of natural frequencies, as well as changes in mode shapes of the
plates and thereby would eventually change the dynamic response
characteristics of the structure. It is also conceivable that the sen-
sitivities of these changes will largely vary with the location, shape
and size of such holes/cut-outs. Even though there exists a large
body of literature investigating these effects for cases of laminated
composites; there appears to be no literature (to the best of the
authors’ knowledge) investigating the effects of hole/cut-out on
the dynamic performance of sandwich composites. It should be
pointed out in this regard that sandwich composite panel differs
significantly from a laminated composite panel since sandwich
panel consists of a ‘‘soft’’ foam core separating the laminated com-
posite face sheets. In fact, the primary advantage of these sandwich
panels is low weight to high strength ratio which has made them
to be indispensable components in modern designs of aerospace
and marine vehicular structures.
Since, there exists no literature on the effects of hole/cut-out on
the dynamic performance of sandwich composite plates; a brief lit-
erature survey is presented for laminated composite plates with
holes/cut-outs and their effects on dynamic performance. Brief lit-
erature survey is also presented for determination of dynamic per-
formance of sandwich composite panels without holes using
modal testing and analysis.
There is an extensive set of literature concerned with determi-
nation of stresses near the hole/cut-out regions in a laminated
composite panel subjected to different types of loading scenarios.
Examples include-axial in-plane loads [1] or thermal loads [2]
resulting in global buckling of the plate or micro buckling of the
fibers [3], free and forced vibration studies with different boundary
conditions [4–8], effects of numerous numbers of hole within a
plate subjected to various loading conditions [9]. Since
holes/cut-outs result in stress concentration and eventually turn
out to be the influential parameters for the design purpose,
researchers have used various closed form solutions [10] as well
as developed different types of finite elements using various
assumptions related to plate theories, such as Rayleigh–Ritz
method [11] equivalent single layer (ESL) theory and multilayer
http://dx.doi.org/10.1016/j.compstruct.2015.05.046
0263-8223/Ó 2015 Elsevier Ltd. All rights reserved.
⇑ Corresponding author. Tel.: +91 3222 283430.
E-mail addresses: suman.subhajit@gmail.com (S. Mondal), alakpatra19@gmail.
com (A.K. Patra), sushanta@civil.iitkgp.ernet.in (S. Chakraborty), nilanjan@civil.
iitkgp.ernet.in (N. Mitra).
Composite Structures 131 (2015) 479–489
Contents lists available at ScienceDirect
Composite Structures
journal homepage: www.elsevier.com/locate/compstruct
2. theory [12] etc. Investigations have been carried out for plates with
different damage criterions to accurately measure stresses near the
holes/cut-outs subjected to different loading scenarios. Optimum
placement of holes/cut-outs in laminated composite panels has
also been investigated [13]. With regards to modal testing of sand-
wich composite panels, there exist experimental and numerical
studies in which the influence of material properties of the core
and the face-sheet (including its layup and orientation) were
investigated [14–20] and found to be significant.
Most recently, researchers [21,22] has performed experimental
and numerical investigations on large amplitude non-linear vibra-
tion of laminated and sandwich composite rectangular plates with
free edges using laser Doppler vibrometer. Zippo et al. [23] con-
ducted experimental investigations on active control of rectangular
sandwich composite plate with carbon fibre reinforced polymer
outer skins and a polymer paper core under free boundary
conditions.
However, there appears to be a lacuna in literature with regards
to the effect of holes/cut-outs on the dynamic performance of
sandwich composite plates. This issue has been investigated and
presented in this paper through a coordinated experimental and
numerical investigation by varying numerous factors such as the
diameter and position of the hole, the thickness of the face sheet
and the core and also aspect ratio of the plate. The effect of these
variations on the dynamic performance of the sandwich composite
plates are then observed and discussed upon.
Details of the process of manufacture of the sandwich compos-
ite plate, as well as the experimental modal testing procedures are
provided in Section 2. Section 3 presents development of a repre-
sentative numerical model for sandwich composites by validating
it with experimental results. Section 4 contains numerical para-
metric studies in which the diameter of the hole as well as its posi-
tion is varied to arrive at various conclusions related to the changes
in natural frequencies for different core and face-sheet thicknesses.
Section 5 provides discussions about the results obtained followed
by Section 6 which concludes the investigations with critical
observations.
2. Experimental investigations
2.1. Manufacture of sandwich composite plate
Closed cell semi-rigid PVC foam of mass density 100 kg/m3
,
having approximate cell size of 400 lm (manufactured by DIAB
Inc. and marketed by the trade name of Divinycell H100) was uti-
lized as the core material for the sandwich composite construction.
The foam was sandwiched between two glass fiber reinforced
epoxy matrix face sheets. The face-sheets typically comprise of
two alternate layers of Woven Roving glass fiber mats (with 276
number of threads per meter as warp and 237 threads per meter
as weft at 90° angle) stitched and assembled with Chopped
Strand glass fiber mat and 1.3 mm thick resin treated plain
Woven Roving glass fiber mat (552 threads as warp and 276
threads as weft at 90° angle). For experimental purpose the thick-
ness of the core considered for sample fabrication was 30 mm and
that of the face sheet was 2.5 mm on either side. EPIKOT resin 828
LVEL with the anhydride hardener EPIKURE curing agent 866 and
the accelerator EPIKURE catalyst 101 of Momentive Specialty
Chemicals (‘‘Momentive’’), Ohio, USA were used for the vacuum
resin infusion work. The resin, hardener and catalyst at the ratio
of 100:80:1.5 by weight were mixed and stirred for 15 min at
150 rpm to eventually make the resin mix system. The resin mix
was infused through the preform (face sheet and core sandwich)
covered by porous Teflon film and highly permeable breather cloth
primarily through vacuum alone. Upon complete part wetting, the
infusion lines were blocked and the full assembly was vacuum
cured at room temperature for at least 40 h. The final fabricated
plate sample having dimension of 400 mm  300 mm was then
utilized for modal testing experiments. Once the modal testing
was completed for a sandwich plate, a concentric hole of
100 mm was drilled and the sample was again modal tested. The
same sample with 100 mm hole was again drilled to obtain
150 mm and then a 200 mm hole and modal testing was per-
formed. The same plate was considered for all the cases – without
any hole and then subsequently, plate with 100 mm, 150 mm and
200 mm drilled holes. This is done to eliminate the possibility of
any inaccuracy arising out of the variations in properties (due to
manufacturing of the plates) had there been different plates with
the specified holes. For each set of experiments at least 3 samples
were tested prior to reporting of any observation which has been
made, based on the mean of the results obtained from experimen-
tal investigations.
2.2. Modal testing of sandwich composite plates
The modal testing investigations were carried out on sandwich
composite plates with and without cut-outs using an instrumented
impact hammer (type 8206-002 of Brüel & Kjær) to excite the
plates and IEPE accelerometer (DeltaTron 4507 of Brüel & Kjær)
to measure the accelerations. A spectrum analyzer (3560-C-L4 of
Brüel & Kjær) [24] was used to conduct the Fast Fourier
Transform of the acquired force and response signals measured
in time domain. The quality of the FRF measurements were
checked using the Coherence function (0–1, 1 for perfect causality)
whether the system output is caused by the system input or by
other factors, e.g. noise, nonlinearity etc. Small tabs of dimensions
20 mm  20 mm  30 mm with holes are attached to the core por-
tion of the plate at the region of minimum distortion to suspend it
freely from supports with rubber bands. The appropriate positions
of the points of suspension are determined from the preliminary
simulation of mode shapes from free vibration analysis of the same
plate in ABAQUS [25], using nominal values of the material proper-
ties. This setup simulates the free boundary condition of the sand-
wich plate with sufficient accuracy [26]. The frequency of
oscillation of the suspended plate is much lower than the frequen-
cies of vibration within the frequency range of interest, thereby
justifying the imposed suspension system as somewhat acceptable
replication of the free boundary condition. Fig. 1(a) shows the
experimental setup for modal testing. Fig. 1(b) shows the sche-
matic diagram of the test including measurement points for excita-
tions and response for a typical sandwich composite plate with a
hole. The plates were discretized into grids of 8 Â 6 with 50 mm
side lengths to get the measurement points. For the acquisition
of response as well as the excitation signals, the accelerometer
was placed at Point 12 (nodal position in a free vibration simula-
tion of the same plate) and the roving hammer procedure was
adopted traversing the entire set of points. Modal tests were
repeated for plates with 100 mm, 150 mm and 200 mm diameter
central hole.
Modal analysis software ME’scopeVES [27] was used to extract
the modal parameters, i.e. the natural frequencies and mode
shapes of the sandwich plates. The measured frequencies are pre-
sented in serial order of observed modes in Table 1. From the
results, it can be observed that central hole/cut-out has signifi-
cantly shifted the modal frequencies of the sandwich plate from
that of the plate with no hole/cut-outs. The presence of central hole
of bigger diameter (e.g. 200 mm) has further reduced the frequen-
cies for most of the lower modes as expected. There is no signifi-
cant change to the mode shapes for the plate with 100 mm or
150 mm diameter holes for the first three modes. However, there
480 S. Mondal et al. / Composite Structures 131 (2015) 479–489
3. are considerable variations in mode shapes for higher modes. It
should be noted that since Table 1 lists the modes in a serial order
it is difficult to comment on mode-switchover issues (i.e. the inter-
change of mode serial numbers due to relative changes in elastic
moduli in orthogonal directions of the plate).
Thereby the similarities and dissimilarities between the exper-
imental mode shapes of the plate with and without holes are
judged using the Modal Assurance Criteria (MAC) [28]. A MAC
matrix having the diametergonal terms approaching unity repre-
sents good correlation, whereas MAC values approaching 0 indi-
cate uncorrelated modes. Only the normalized vertical
components of the eigenvectors at selected nodes are considered.
Fig. 2 shows superposed plots of mode shapes for plates with-
out hole and plates with 100 diameter concentric holes. The
matching of the modes and representation in the superposed dia-
gram has been done based on MAC correlation matrix between
the two cases. It can be observed from the figure that first four
modes correlates serially, whereas the 5th mode of the sandwich
plate with 100 mm hole matches well with the 6th mode of the
plate without hole. Similarly, the 6th mode of the sandwich plate
with 100 mm hole matches well with the 5th mode of the plate
without hole. The 7th modes for both the plates correlate well seri-
ally again. It may be noted that the 8th modes of the plate without
hole and with 100 mm hole shows a very low value of MAC;
thereby indicating that these modes are not correlated.
It may be possible that a correlation might exist with a higher
mode of the plate with 100 mm hole. Similar comparisons have
been made for the other two cases of 150 mm and 200 mm concen-
tric holes with the case of a plate with no hole. For space brevity
the detailed plots (like Fig. 2) has not been presented and only
the MAC correlation matrix has been presented in Fig. 3. The two
horizontal axes (in Fig. 3) indicate the modes for sandwich plates
with and without hole. The vertical axis indicates the MAC correla-
tions at corresponding modes. The other off-diametergonal values
do not correlate well as is obvious from the diagram. A value of 60%
MAC correlation has been arbitrarily fixed as an acceptance crite-
rion for good correlation in between modes.
The corresponding MAC correlations for plate without hole and
the plate with 150 mm hole have been plotted in Fig. 3(a). It can be
observed that the 4th, 5th and the 6th modes switch over amongst
themselves for the plate without hole and the plate with 150 mm
diameter hole.
Similar observations have been made for the MAC correlations
between the plate without hole and the plate with 200 mm diam-
eter hole. It is noted that the 4th mode of the plate without hole is
correlating well with the 6th mode of the plate having 200 mm
diameter hole. Similarly the 6th mode of the plate without hole
is correlating well with the 7th mode of the plate having
200 mm diameter hole as shown in Fig. 3(b). This type of mode
switchover happens due to the relative directional changes in a
plate, for example, after incorporating holes the direction of the
plate in which the plate was stiffer may become relatively flexible
and therefore from energy consideration, it will be easier for the
plate to deform into that direction first. The natural frequency is
basically the ratio of changes in the potential energy (hence stiff-
ness) and kinetic energy (hence mass); thereby the diameter and
location of the hole determines the relative loss or gain of potential
and kinetic energy whose ratio determines the changes in natural
frequency.
3. Representative finite element modeling of sandwich
composite plates
In the present investigation, an 8 noded three dimensional solid
brick elements (C3D8R) have been used to model the sandwich
plate in ABAQUS. Perfect bond has been used between the face
sheets and the core using tie constraints assuming no existence
of interlaminar delamination between the face sheets and the core.
The dimension of the sample plate is taken as 300 mm  400 mm
with 30 mm thick core and 2.5 mm face sheet on either sides
(Fig. 4(a)) and a typical finite element mesh division for modeling
the plate with 100 mm diameter hole as shown in Fig. 4(b). Similar
models have been developed for plate with concentric holes of
diameter 150 mm and 200 mm but have not been shown here.
Fig. 1. (a) Modal testing of a sandwich composite plate with cut-out, (b) schematic diagram of sandwich plate with 100 mm diameter hole.
Table 1
Experimentally measured frequencies of the FRP plate under free boundary condition.
Mode
No.
Plate
without
hole (Hz)
Plate with 100
diameter
central hole
(Hz)
Plate with 150
diameter
central hole
(Hz)
Plate with 200
diameter
central hole
(Hz)
1 429.56 382.55 334.07 266.81
2 637.72 600.75 560.94 503.465
3 849.45 808.66 773.95 726.378
4 928.17 926.79 892.13 865.683
5 1024.90 946.20 936.84 942.51
6 1101.10 1023.0 996.28 1087.67
7 1254.31 1233.5 1174.7 1317.81
8 1498.53 1337.9 1340.67 1337.72
S. Mondal et al. / Composite Structures 131 (2015) 479–489 481
4. Convergence studies have been performed with reduced mesh
sizes to find out suitable discretization for determining the fre-
quencies and mode shapes of the sandwich plates. The final
selected mesh sizes are 5 mm on all sides for the core and
10 mm  10 mm  1.25 mm for the face sheets. Only free bound-
ary condition has been explored. A shifted block Lanczos algorithm
has been utilized to obtain the eigenvalues and eigenvectors.
It should be noted that the values of the in-plane Young’s
moduli (i.e. Ex and Ey) and the shear moduli (Gxy,Gyz,Gxz) are
estimated through a model updating exercise by correlating the
experimentally observed frequencies and mode shapes with the
results obtained from an initial finite element model. The densities
of the core as well as of the face-sheets are determined experimen-
tally and the Poisson’s ratios (isotropic value for the core and
in-plane Poisson’s ratio txy and out-of-plane Poisson’s ratios txz
and tyz for the face sheets) are assumed nominally. It should also
be noted that the modes considered for the current investigation
is not sensitive to the value of Young’s modulus of the face sheet
in thickness direction, i.e. Ez (which is taken to be considerably
smaller than Ex or Ey). For the core region, since it is assumed to
Fig. 2. Typical comparisons of mode shapes for plate without hole (P0) and plate with 100 diameter hole (P100).
Fig. 3. (a) MAC values between the test plate with 150 mm hole (P150) and plate without hole. (b) MAC values between the test plate with 200 mm hole (P200) and plate
without hole.
482 S. Mondal et al. / Composite Structures 131 (2015) 479–489
5. be an isotropic material, the value of Young’s modulus has been
taken to be same in all directions.
For the present investigation the gradient based Inverse
Eigensensitivity Method (IEM) [29] implemented through the soft-
ware FEMTools [30] has been used to obtain the updated Young’s
moduli and shear moduli. The elastic material values thus obtained
are shown in Table 2. These values are assumed to be constants for
further numerical investigations.
A typical mode shape comparison of the experimental modes
and finite element modes with updated material properties of
the plate without hole is shown in Fig. 5. The corresponding MAC
values are also shown to indicate the degrees of correlation
between modes.
Similarly, the MAC values between the experimental and
numerical mode shapes for the sandwich plate with concentric
holes are computed. The values corresponding to 100 mm
diameter hole and 150 mm diameter hole are presented in Fig. 6.
It can readily be observed that the modes correlate quite well.
Thereby a representative numerical model has been established.
4. Numerical experimentation
An extensive numerical experimentation has been carried out
using the representative finite element model established in the
previous section. The objective of this numerical experimentation
is to understand the relationship between different variables sen-
sitive to the dynamic behavior of sandwich composite plates.
Parameters of interest are thickness of the core, thickness of the
face sheets, as well as the diameter and positions of the circular
holes or cut-outs and the aspect ratio of the plate. Initially, one
or two of the parameters are varied, keeping the others constant
Fig. 4. (a) Schematic diagram of the sandwich plate (b) finite element discretization of the plate with a hole.
Table 2
Material property of sandwich composite plate.
Material parameter Core Face-sheet
E 1.19 N/m2
–
Density (q) 100 kg/m3
1400 kg/m3
Poisson ratio (t) 0.3 –
Ex – 1.446E10 N/m2
Ey – 1.35E10 N/m2
Ez – 6E7 N/m2
Gxy – 3.27E9 N/m2
Gxz – 5.47E6 N/m2
Gyz – 4.831E6 N/m2
txy – 0.32
txz ¼ tyz – 0.10
Fig. 5. Comparison experimental and finite element mode shapes.
S. Mondal et al. / Composite Structures 131 (2015) 479–489 483
6. to understand the nature of variations in dynamic responses, indi-
cated by the changes in natural frequencies.
4.1. Variation of frequencies with core thickness
The core thickness was taken as 30 mm for the experimental
case studies. In this numerical investigation, the lower and the
upper limits of the core thickness have been chosen as 15 mm (half
the experimental core thickness) and 60 mm (twice the
experimental core thickness). The results for plate without hole
and for the plates with various concentric holes such as 100 mm,
150 mm, 200 mm have been plotted in Fig. 7.
It can be observed from Fig. 7(a) that the frequencies increase
monotonically at all modes with increasing core thickness for the
plate without hole. Similar observations could be made for lower
modes in plates with different concentric holes (refer Fig. 7(b)–(d)).
However, this type of pattern could not be observed for higher
modes for plates with holes. The result for this deviation in pattern
Fig. 6. MAC value for sandwich plate (a) with 100 mm diameter hole and (b) with 150 m diameter hole.
Fig. 7. Frequency variation with core thickness for sandwich plate without and with holes.
484 S. Mondal et al. / Composite Structures 131 (2015) 479–489
7. can be attributed to drastic relative reduction in stiffness due to
hole as compared to reduction in mass for certain modes at certain
core thicknesses. Thereby from this observation it may be entirely
possible to increase the frequency of a sandwich plate with hole
especially for higher modes. It is necessary to perform detailed
dynamic analysis prior to fix design criteria for sandwich plates
with holes.
4.2. Variation of frequency with respect to face-sheet thickness
In these sets of simulations, the variation of natural frequencies
of the sandwich plates with respect to the changes in face-sheet
thicknesses on both faces are investigated, keeping the core thick-
ness constant (i.e. 30 mm). The thickness of the face sheets is varied
from 1.25 mm to 5 mm (half and twice of the face sheet thickness of
the experimental sandwich plate respectively). The variations of
frequencies are found to be mostly monotonically decreasing for
the plate without a hole (Fig. 8(a)). Similar observations could be
made for almost all modes in plates with different concentric holes
(refer Fig. 8(b)–(d)) with the exception of 7th and 8th mode for
plate with 200 mm hole. The result for this deviation in the pattern
can be attributed to relative increase in stiffness due to hole as com-
pared to increase in mass for certain modes at certain face-sheet
thicknesses. This observation once again supports a thorough
dynamic analysis prior to taking any design decisions.
4.3. Variation of frequencies with combined changes in core and face-
sheet thicknesses
If an operating frequency range is provided for the sandwich
plate, then it is necessary to determine whether introduction of a
hole would change the dynamic response of the plate significantly.
There may be various combinations of core and face sheet thick-
nesses which can satisfy the requirements of a particular frequency
band. It may not always be effective to increase the frequency of
the plate by increasing the core thickness or by reducing the face
sheet thicknesses. Thereby it is necessary to observe the combined
effect of both the core and face-sheet thickness on the dynamic
responses of sandwich composite plates with holes. In order to
obtain an insight about the variation in dynamic responses from
the numerical experimentation, only two lower modes (fundamen-
tal and 2nd mode corresponding to torsional and flexural
responses respectively) and two higher modes (6th and 7th corre-
sponding primarily to torsional and bending responses respec-
tively) are presented in Fig. 9. The effects of the other modes
have not been presented due to space restrictions. The legend in
these figures indicates the diameter of the hole first, followed by
the face sheet thickness, e.g. ‘‘Hole 100 face 1.25’’ means the plate
is having a concentric hole of 100 mm diameter with face sheet
thickness 1.25 mm on both sides.
For the fundamental mode (as observed in Fig. 9(a)) there
appears to be a monotonic increase in the variation of frequencies
with increasing core thickness and corresponding decrease in
face-sheet thickness. However, for the 2nd mode (Fig. 9(b)), as
the diameter of the hole increases, there is a non-uniform variation
of the frequencies for certain core and face-sheet thickness combi-
nation. For example, with 5 mm face sheet thickness the frequency
of the 2nd mode almost remains same even after increase of the
core thickness from 40 to 50 mm for sandwich plate with
200 mm hole. Moreover, the frequency dips down for 5 mm face
sheet thickness with 150 mm hole compared to the 200 mm hole
as the core thickness is increased from 50 to 60 mm. Similar trends
Fig. 8. Frequency variation with face sheet thickness for sandwich plate without and with holes.
S. Mondal et al. / Composite Structures 131 (2015) 479–489 485
8. of non-uniform variations could be observed at higher modes in
Fig. 9(c) and (d). This apparently weird behavior of overall loss of
stiffness of the sandwich plate with bigger diameter holes could
not be compensated enough by increasing the core thickness.
Hence the global natural frequency of the plate reduces despite
the fact that there is an increase in core thickness. Similarly, there
may not be any increase in stiffness even after decrease of face
sheet thickness for larger diameter of the holes.
The curves thus prepared can also be used to determine readily
a particular set of parameters against a desired frequency range of
interest. For example, if it is known that the frequencies of opera-
tion of a sandwich plate needs to be confined between 300 and
400 Hz, ranges of appropriate values of face sheet thicknesses
can be selected for a chosen value of core thickness in the design
so that the 1st fundamental frequency falls within this range.
Similarly, appropriate values of core thickness can be selected for
a chosen face sheet thickness and a frequency band. Similar inves-
tigations can be carried out for higher modes as well.
The same set of curves can also be utilized to decide about the
limiting values of frequencies that may be affected by the choice of
a particular set of values of core and face sheet thicknesses with
certain pre-decided diameter of hole.
4.4. Variation of frequencies with respect to changes in the position of
hole
Variations of frequencies can be represented graphically by sets
of curves drawn for various locations of the hole. Fig. 10 shows one
such set of frequency variations for 100 mm central diameter of the
hole, with core thickness 30 mm and face sheet thickness 2.5 mm.
The hole maintains a minimum distance of 50 mm from the edge.
Case 1 depicts the variation of frequencies with a concentric hole;
Fig. 9. Frequency variation of modes for different combination of core and face sheet thickness and diameter of the hole for (a) 1st mode (b) 2nd mode, (c) 6th mode (d) 7th
mode.
Fig. 10. Change in frequencies for various locations of 100 mm hole with core
thickness 30 mm and face sheet thickness of 2.5 mm.
486 S. Mondal et al. / Composite Structures 131 (2015) 479–489
9. whereas Case 2, Case 3 and Case 4 represents the frequency varia-
tions for plate with holes eccentric along the longitudinal axis,
transverse axis and diagonal axis respectively, maintaining the
prescribed minimum distance of 50 mm from the nearest edge.
From Fig. 10 it can be observed that the variations in frequen-
cies are not substantial for lower modes but are considerable at
certain higher modes for different positions of holes. Significant
increase in frequency is observed at the 6th mode for Case 2 and
3. This may be explained in conjunction with the 6th mode shapes
of the plate with 100 mm concentric hole (Fig. 2). The shifting of
the hole from the centre towards the direction of smaller radius
of curvature of the plate will result in more incremental changes
to the frequencies. From the figure it is clear that the most effective
average reduction considering all frequencies can be achieved in
Case 2 i.e. plate with holes eccentric along the longitudinal axis.
4.5. Variation of frequencies with respect to diameter of hole located
along the diagonal
Investigations have been carried out to determine the relation-
ship of variation of frequencies with core thickness for various face
sheet thicknesses and hole diameters, when the hole is placed
eccentrically as explained in Fig. 11. It may be noted that the pre-
scribed minimum distance of the hole is maintained at 50 mm
from any side of the plate. It is interesting to note that the variation
of frequencies at higher modes will have many non-uniform vari-
ations as shown in Fig. 12.
Distribution of stiffness within the plate becomes further lop-
sided as the diameter of the eccentric hole (along the diagonal) is
increased, keeping minimum prescribed distance from the sides.
Frequencies of the plate vary widely for different combinations of
core and face sheet thicknesses and may have intersections in the
Fig. 11. Locations of eccentric hole having different diameters in the sandwich
plate.
Fig. 12. Frequency variation of modes for different combination of core and face sheet thickness and diameter of hole located at corner keeping minimum 50 mm distance
from edge for (a) 1st mode (b) 2nd mode (c) 6th mode (d) 7th mode.
S. Mondal et al. / Composite Structures 131 (2015) 479–489 487
10. curves, as is apparent for some of the higher modes as shown in
Fig. 12. For example, in the case of 200 mm eccentric hole, the fre-
quency of the 6th mode of the plate with 1.25 mm face sheet
decreases whereas the frequency increases for 2.5 mm face sheet.
The core thickness has the same incremental increase from 30 to
40 mm in both cases. The increase in frequency due to reduction
of face-sheet thickness is counterbalanced by the corresponding
increase due to loss of stiffness with increase in diameter of hole.
4.6. Variation of frequencies with plate aspect ratio
The investigations so far have been restricted to a sandwich
plate of size 400 mm  300 mm. This aspect ratio has been prelim-
inary selected so as to avoid closely spaced and/or repeated modes
which may occur in square plates or plates having aspect ratio
exactly of multiples of integers. The effects of aspect ratio of the
plate on the frequencies have now been extended further to
include a few more rectangular configurations, yet maintaining
aspect ratios which result into mostly well separated modes.
Rectangular plates of dimensions 300 mm  200 mm and
500 mm  300 mm are investigated to observe if there exists any
difference in the observed dynamic characteristics of the sandwich
plate with holes. The results of the variations of the fundamental
frequency for the plate without hole and with concentric hole of
diameter 100 mm for different plate aspect ratios are presented
in Fig. 13. Other results are not presented for brevity.
Here, 3Â2_1.25 means the size of the plate is 300 mm  200 mm
and the face sheet thickness is 1.25 mm on both sides, whereas the
core thickness is kept constant (30 mm).
It may be observed from Fig. 13 that the trends of the curves
showing variations of frequencies have not changed as the aspect
ratio of the plate is altered. This may be explained from the fact that
the basic dynamic characteristics, i.e. the pattern of the mode
shapes, have not changed significantly for the present investigations
related to the rectangular plate for the chosen ranges of aspect ratios.
5. Discussions
An exhaustive mixed experimental–numerical study has been
presented investigating as to how the dynamic performance of a
sandwich composite plate is affected by the introduction of holes.
The study also provides guidelines on what combinations of design
parameters, such as the core thickness, face-sheet thickness, diam-
eter of hole and its position are desirable to keep the dynamic per-
formance (such as, the natural frequencies of the sandwich plate)
within desired values. In case, some sophisticated instruments
are to be mounted or structural modifications are sought in terms
of proposed service holes at designated locations. The changes in
frequencies at various modes can only be predicted by conducting
such rigorous studies. The investigation of changes in frequencies
with respect to core thickness and face sheet thicknesses for plate
with a hole, indicates that for higher modes, the frequencies may
not increase with increase of core thickness or with decrease of
face sheet thickness. This indicates a possibility of an optimum
diameter of hole beyond which, increase in core thickness may
not be an effective measure to increase the frequency of the plate,
especially for higher modes. Same is applicable for the face sheet
thicknesses: the higher modal frequencies cannot be increased
by decreasing the face sheet thicknesses beyond certain core thick-
ness. The study demonstrates that the frequency reduces towards
the minimum as the hole moves off-centre towards the larger side
of the plate. It has been observed that the particular modes which
are affected the most for different plates will be dependent upon
the combined effects of core thickness, face-sheet thicknesses
and the aspect ratio of the plate, as well as diameter and location
of the hole. A thorough dynamic investigation is always necessary
for further modification of the design of the sandwich plate for
required dynamic performance.
6. Conclusions
Investigations have been carried out for sandwich plates with
holes at various locations to determine the effects of core thick-
ness, face sheet thicknesses, diameter of the hole and aspect ratio
of the sandwich plate on the changes in frequencies of various
modes. It has been observed that all the above mentioned param-
eters are contributing to the changes in dynamic responses and a
detailed analysis can only ascertain the correct combination of
the parameters for achieving a desired dynamic performance of
such sandwich plates. The variation of frequencies may not be
always monotonic for higher modes for sandwich plate with holes.
The study is limited to rectangular sandwich plates with circular
through holes only. Free boundary condition has been only
explored in this study.
Fig. 13. Variations of frequencies with core thickness of plate for different aspect ratios for (a) plate without hole, (b) plate with 100 mm diameter hole.
488 S. Mondal et al. / Composite Structures 131 (2015) 479–489
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