Failure analysis of pin loaded glass epoxy polystyrene composite plates
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Failure analysis of pin loaded glass epoxy polystyrene composite plates

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    Failure analysis of pin loaded glass epoxy polystyrene composite plates Failure analysis of pin loaded glass epoxy polystyrene composite plates Document Transcript

    • International Journal of Advanced Research in OF ADVANCED RESEARCH IN INTERNATIONAL JOURNAL Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEME ENGINEERING AND TECHNOLOGY (IJARET)ISSN 0976 - 6480 (Print)ISSN 0976 - 6499 (Online) IJARETVolume 3, Issue 2, July-December (2012), pp. 137-144© IAEME: www.iaeme.com/ijaret.htmlJournal Impact Factor (2012): 2.7078 (Calculated by GISI) ©IAEMEwww.jifactor.com FAILURE ANALYSIS OF PIN LOADED GLASS EPOXY/POLYSTYRENE COMPOSITE PLATES D.Lingaraju1, *, K.Srinivas2, B.A.Ranganath2 1. Aditya Institute of Technology and Management, India (*Corresponding Author) 2. Maharaj Vijayaram Gajapati Raj College of Engineering, India ABSTRACT Composites are becoming an essential part of today’s materials because they offer advantages such as low weight, corrosion resistance, high fatigue strength, faster assembly etc. Composites are used as materials in making aircraft structures to golf clubs, electronic packaging to medical equipment and space vehicles due to their good mechanical properties. In the practical use of the composite materials in structures, some geometrical discontinuities like cut outs and holes are necessary for some functions such as riveted and bolted joints. Therefore it is necessary to study the failure behaviour at these joints. In this study, behaviour of pin loaded laminated composite plates with different dimensions are observed experimentally. The aim is to investigate the stress and failure load and failure mode in laminated glass epoxy/polystyrene composite plates with one circular hole. The hole of the plate is subjected to a traction force by rigid pin. The analysis is then extended to find the effect of varying K/D and W/D. It is observed that the strength of the specimen increases with the increase in K/D and W/D to an extent and then becomes constant. W/D has a greater effect on the mode of failure. Keywords: Pin Load, Failure analysis, FRP, Epoxy, Polystyrene. INTRODUCTION Composite civil and mechanical structures are appearing more frequently in load-bearing applications because of their low cost, lightweight and environmental resistance. Low cost glass-fiber/plastic composites are used in the process industry when the environment is highly hostile and metal corrosion is a serious problem. In the practical use of the composite materials in structures, some geometrical discontinuities like cut outs and holes are necessary for some functions such as riveted and bolted joints. Therefore it is necessary to study the failure behaviour at these joints. For this reason and because civil structures are designed for 137
    • International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976– 6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEMElongevity, it is becoming increasingly important that engineers have tools to designcomposite structures for both life and strength. Typical failure mechanisms for the pin loaded-joint configuration are shown inFigure-1. The joint fails in one of these three modes or a combination of these. The strengthof the joint is the least of normal, shearing and bearing strengths. The mode of failuredepends on the type of strength which is the least. In general, failure of a joint means eitherthe failure of the plate or the failure of the pin / joint. The normal mode of failure occurs forplate while shearing and bearing modes of failure occur either for plate or pin depending onwhich is weaker. In the present work, the pin is considered to be rigid and therefore thefailure is considered only in the plate. (a) (b) (c) Figure-1: Modes of failure (a) Normal (b) Shear (c) BearingFU-KUO Chang et.al. [1] Studied the progressive damage model for notched laminatedcomposites subjected to tensile loading. The model is capable of assessing damage inlaminates with arbitrary ply-orientations and of predicting the ultimate tensile strength of thenotched laminates. The failure strength and failure mode of bolted connections of glass woven fabriccomposites was investigated by H.J.LIN et.al. [2]. the failure criteria and the materialdegradation model were successfully used to model the behaviour of laminates subjected toin-plane loads. They considered five types of failures: matrix failure in tension, matrix failurein compression, fiber failure in tension, fiber failure in compression and fiber- matrix de-bonding failure. Experimental results showed that laminates with moulded-in holes arestronger when the edge distance is small. When the edge distance is large, specimens withmoulded-in holes have about the same strength as those with drilled holes. Camanho et.al. [3] developed a three-dimensional finite element model to predictdamage progression and strength of mechanically fastened joints in carbon fiber-reinforcedplastics that fail in the bearing, tension and shear-out modes. Aktas et.al. [4] investigatedfailure strength and failure mode of a mechanically fastened carbon-epoxy composite plate ofarbitrary orientation. Bearing strength and failure modes were taken as functions of threevariables: orientation angle of fibers, E/ D, and W/ D. By changing the value of one of thevariables while keeping the values of the others constant, experimental and numericalanalyses were performed. Dano et.al. [5] carried out analysis on single mechanically fastened joint in fiber-reinforced plastics. A finite-element model was developed to predict the response of pin-loaded composite plates. The model takes into account contact at the pin-hole interface,progressive damage, large deformation theory, and a non-linear shear stress-strainrelationship. 138
    • International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976– 6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEME Bulent Murat Icten et.al. [6] investigated the possibility of predicting the properties ofthe joint from the properties of the material measured with standard tests. A compositerectangular plate of length L+E and width W with a hole of diameter D, with a hole at adistance E, from the free edge of the plate was taken as the specimen. A rigid pin was locatedat the center of the hole and a uniform tensile load P was applied to the plate. A compressiontesting was applied to the specimen to fan-out failure in net tension, shear out mode, andbearing mode. A progressive damage model was applied which consisted of three: stressanalysis, failure criteria, and property degradation rules. The two dimensional finite elementmethod was used to determine the failure load and failure mode using Hoffman and Hashincriteria. The mechanical properties of the composite material were obtained from standardtests. Load displacement curves for various W/D, the effect of W/D ratio, and orientation onbearing strength were plotted and results were in close agreement with the experimentalresults. Okutan et.al. [7] performed an investigation to study the response of pin-loaded andlaminated composites. Tensile tests were performed on E/glass epoxy composites for twodifferent ply orientations such as [0/±45] s and [90/±45] s. For each ply orientation, 20different geometries were chosen. The major focus of the study was to characterize the failuremechanisms and to evaluate the effect of geometric dimensions on the bearing, shear-out andnet tension strengths of pinned joints. For this purpose, the specimens were tested to find firstfailure and final failure load. Tayfun Gulem et.al. [8] carried out a study to deal with thebearing strength, failure mode and failure load in a woven laminated glass vinyl estercomposite plate with circular hole subjected to a traction force by a rigid pin. Theyinvestigated for two variables; the distance from the free edge of the plate to- the diameter ofthe hole (E/D) ratio and the width of rectangular plate-to-the diameter of the hole (W/D) rationumerically and experimentally. The effects of preload moment, moisture and interference-fit on bearing strength andfailure mode in pin-jointed and bolted carbon–epoxy plates which were subjected to atraction force studied by Servet Kapti et al. Two different geometrical parameters, enddistance to pin diameter ratio (E/D) and width to pin diameter ratio (W/D), were consideredexperimentally. E/D and W/D ratios were selected ranging from 1 to 4 and from 2 to 4,respectively. The test results showed that the ultimate failure loads were directly affected bythe geometrical parameters, preload moments and interference-fit. Tsai-Wu criterion wasused to determine bearing strength corresponding to first failure load [9]. Alaattin Aktas et al. [10] studied the Failure load and failure mode of glass-epoxycomposite plates with single and double parallel pinned-joints have analysed experimentallyand numerically. Two variables were investigated during analyses; the distance from the freeedge of plate to the diameter of the first hole (E/D) ratio (2, 3, 4, 5), and the width of thespecimen to the diameter of the holes (W/D) ratios (2, 3, 4, 5). The effect of the clearance and interference-fit on the failure mode, failure load andbearing strength of the pin-loaded joints subjected to traction forces are examined by Binnuret al. [11]. A failure investigation was performed to determine the failure mode and bearingstrength of mechanically fastened bolted-joints in glass fiber reinforced epoxy laminatedcomposite plates, experimentally. Two different geometrical parameters, the edge distance-to-hole diameter ratio (E/D) and plate width-to-hole diameter ratio (W/D) were considered.For this purpose, E/D ratio was selected from 1 to 5, whereas W/D ratio was chosen from 2 to5. since an important target of this study was observed by Faruk Sen et al. [12] and reportedthe changing of failure mechanism under various preloads. 139
    • International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976– 6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEME July December With the above study it has observed that a progressive damage analysis consists ofthree important steps: stress analysis, application of failure criteria and degradation ofmaterial properties according to failure mode.EXPERIMENTAL STUDY In this study, composite materials rectangular plates (length L, Width W, Thickness t) ,made on fiber-reinforced woven rove mat with a circular hole filled with rigid pin is used.The diameter (D) of the hole is fixed at a constant value of 5mm. The hole is located along hethe central line of the plate at a distance K from end of the plate. A uniform tensile load P isapplied to the plate. Load is parallel to the plate and is symmetric with respect to the central respectline. Thus, the load cannot create bending moments about X, Y, Z axis. The set up is shown ,in figure-2. Figure-2: Geometry of a laminated composite plate with circular hole Geometry parameters: specimen width (W) or ratio of width to hole diameter (W/D),edge distance(K)or ratio of the edge distance to hole diameter(K/D), Specimen thickness )or /D),(t),hole ratio(D)and pitch for multiple joints and the Length of the plate is L. h TESTING PROCEDURE To find the failure load and the failure mode, a series of experiments were performed. performedThe specimens were trimmed as depicted in figure The effects of the pin location were e figure-3.studied by varying the width to diameter (W/D) ratio from 3 to 5, edge distance to diameter ,(K/D) ratio from 1, 2 and between two holes distance to diameter (K/D) ratio from 1 and 2. The experiments were carried out in tension mode on the Universal Testing Machine.The lower edge of the specimen clamped and loaded from the steel pin by stretching thespecimens at a ratio 0.5 mm/min is shown in Figure-3. The load pin displacement diagrams .for all composite configurations were plotted. Figure-3: Experimental setup for pin joint testing and test specimens (epoxy/ polystyrene polystyrene) 140
    • International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976– 6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEMETESTING Take the specimen holder and place the specimen in the holder using the pins andplace that one in the UTM machine to get the shear and tension properties of that specimenand the load that withstand the plate and the deflection are as tabulated. The specimens with varying K/D and W/D the specimen failure, the load at which itcan withstand is observed and the graphs and the results are discussed. In the analyses thediameter of the hole and the thickness of the plate were taken as constant. To understand thefailure behavior of specimens with K/D and W/D, a parametric study was done and presentedin this Paper.Effect of variation in K/D The diameter of the pinhole is kept constant and the W/D, K/D are varied to find thefailure load. The effect of W/D, K/D are studied by taking the diameter of hole as D = 5 mmand for each value of this diameter K/D is varied as 1 2, 3 whereas W/D is varied as 3, 4, 5.Here W/D is varied when K/D=2. This brings up 9 different specimen models obtained fromcombinations of W/D and K/D. Load is applied on each specimen model till failure takesplace. The failure load and failure mode are noted. 250 W/D epoxy BEARING STRENGTH 200 =3 150 100 50 0 1 K/D 2 3 Figure-4: Bearing strength Vs K/D at W/D=3 for epoxy and polystyreneFig-4 to 6 shows the graphs plotted between the Bearing strength and K/D. The observationsfrom this graph are as follows: Bearing strength of different specimens with same W/D, K/D is found to increase with increasing W/D. This is because of the change in the width of the specimen. As W/D increases, the failure mode will be normal and shear. Firstly, it will be normal and by increasing the W/D value, the normal becomes shear. The bearing strength will slightly increase and become constant. Bearing strength for a specific diameter value initially increases as K/D increases, and then almost becomes constant with further increase in K/D. keeping D as constant, when K/D increases, the distance of the hole from one edge of the plate increases i.e. the hole simply shifts its position away from the edge of the plate towards the centre of the plate. This increases the shear strength of the specimen. 141
    • International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976– 6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEME 300 BEARING STRENGTH W/D =4 200 EPOXY 100 0 1 K/D 2 3 Figure-5: Bearing strength Vs K/D at W/D=4 for epoxy and polystyrene. 300 W/D=5 BEARING STRENGTH 200 epoxy 100 0 1 2 3 K/D Figure-6: Bearing strength Vs K/D at W/D=5 for epoxy and polystyreneEffect of variation in W/D The effect of W/D is studied keeping the diameter of hole as D = 5mm and for eachvalue of this diameter W/D is varied as 3, 4 and 5. Initially K/D is kept constant at 1and W/Dat 3. This brings up 9 different specimen models obtained from combinations W/D ratio.Load is applied on each specimen model till failure takes place. Bearing strength and failuremodes are noted. Graphs are plotted between the failure load and W/D for different values of K/D.From these figures the following observations are made while in case of epoxy as thematerial of the plate the following conditions are observed As K/D=1 is kept constant and then increasing W/D value results in increasing of Bearing strength, as that increases slightly and then kept constant this will because that the varying in width of the specimen and D as constant. the failure mode of the specimen are normal and shear takes place As K/D=2 is kept constant and varying the distance between hole and edge then increasing W/D value, then Bearing strength will increase as that increases and becomes decrease slightly and then it fails. This is because of the varying in width of the specimen and the distance between edge and hole and D as constant. Bearing is the failure type of mode. 142
    • International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976– 6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEMEWhile in case of polystyrene as the material of the plate, the following conditions areobserved As K/D=1 is kept constant, then increasing W/D value, then Bearing strength will increase as that increases slightly and then kept constant. This is because of the varying in width of the specimen and D as constant. The failure mode of the specimen are normal and shear takes place As K/D=2 is kept constant, then increasing W/D value, the Bearing strength will increase as that increases and becomes decrease slightly and kept constant This is because of the varying in width of the specimen and D as constant. The failure mode of the specimen is bearing. Table-1: W/D along bearing strength and failure mode Epoxy Bearing Failure Polystyrene Bearing Failure Strength Mode Strength Mode K=1 150.85 S W/D=3 K=1 27.65 S W/D=3 K=2 192.46 S K=2 53.73 B K=3 194.24 B K=3 67.11 B W/D=4 K=1 132.72 B W/D=4 K=1 28.46 B K=2 240.94 B K=2 33.82 B K=3 246.78 B K=3 48.83 B W/D=5 K=1 145.36 B W/D=5 K=1 30.26 B K=2 260.42 B K=2 33.33 B K=3 267.46 B+S K=3 40.22 B+S As compared to both the materials the strength is more to epoxy material and it can withstand high Bearing strength as compared to the polystyrene material composite plateCONCLUSIONS In the present work failure analysis on double pin loaded glass epoxy/polystyrenecomposite plates is performed for different values of E/D, K/D, and W/D. The followingconclusions are drawn from this analysis. • The analysis to find the effect of varying K/D and W/D. It is observed that the strength of the specimen increases with increase in K/D and W/D to an extent and then becomes constant. W/D has a greater effect on the mode of failure. • The failure load of the specimen increases with increase in K/D as a result of increase in edge distance of the specimen and becomes constant for higher values. • The failure load of the specimen increases with increase in K/D as a result of increase in edge distance of the specimen and becomes constant for higher values. • As W/D increases the failure load initially increases then decreases or becomes constant as a result of increasing stress concentration factor. • As the thickness of the specimen increases the failure load increases as a result of increase in cross sectional area of the specimen. 143
    • International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976– 6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEMEREFERENCE1. Fu-Kuo Chang, Kuo-Yen Chang, (1987) “A Progressive Damage Model for LaminatedComposite Containing Stress Concentrations”. Journal of Composite Materials, 21, 834-855.2. H. J. Lin & C. C. Tsai, (1995) “Failure Analysis of Bolted Connections of Compositeswith Drilled And Moulded-In Hole”, Composite Structures, 30, 159-168.3. P.P. Camanho and F.L. Matthews, (1999) “A Progressive Damage Model for MechanicallyFastened Joints in Composite Laminates”, Journal of Composite Materials, 33(24) 2248-2279.4. AlaattIcn Aktas, Ramazan Karakuzu, (1999) “Failure Analysis of Two- DimensionalCarbon-Epoxy Composite Plate Pinned Joint”, Mechanics of Composite Materials andStructures, 6, 347–3615. Marie-Laure Dano, Guy Gendron and Andre Picard, (2000)” Stress and Failure AnalysisOf Mechanically Fastened Joints In Composite Laminates”, Composite Structures, 50, 287-2966. Bulent Murat Icten and Ramazan Karakuzu, (2002)” Progressive Failure Analysis of Pin-Loaded Carbon–Epoxy Woven Composite Plates”, Composites Science and Technology, 62,1259–1271.7. Buket Okutan and Ramazan Karakuzu, (2003) “The Strength of Pinned Joints inLaminated Composites”, Composites Science and Technology, 63, 893–905.8. Ramazan Karakuzu, Tayfun Gulem, Bulent Murat Icten, (2006)” Failure Analysis ofWoven Laminated Glass–Vinylester Composites with Pin-Loaded Hole”, CompositesScience and Technology, 72, 27–329. Servet Kapti, Onur Sayman, Mustafa Ozen, Semih Benli, (2010) “Experimental andnumerical failure analysis of carbon/epoxy laminated composite joints under differentconditions”, Materials and Design 31, 4933–494210. Alaattin Aktas, Huseyin Imrek, Yusuf Cunediog˘lu, (2009) “Experimental and numericalfailure analysis of pinned-joints in composite materials”, Composite Structures 89, 459–46611. Binnur Gören Kiral, (2010) “Effect of the clearance and interference-fit on failure of thepin-loaded composites”, Materials and Design 31, 85–93.12. Faruk Sen, Murat Pakdil, Onur Sayman, Semih Benli, (2008) “Experimental failureanalysis of mechanically fastened joints with clearance in composite laminates underpreload”, Materials and Design 29, 1159–1169. 144