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1. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 07 | July 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 2111
NON-DESTRUCTIVEsDETECTIONs&sCHARACTERIZATIONs OFs
DAMAGESsINsHONEYCOMBsCOMPOSITEsSTRUCTURES
Sangita Kumari1, Er. Rahul Malik2,
1M.tech Student, P.M. Group of Institutions, DCRUST Murthal, Sonipat, Haryana
2Head of Department, Mechanical Engineering, P.M. Group of Institutions, DCRUST Murthal, Sonipat, Haryana
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Abstract –This thesis discusses many existing methods of
non-destructive evaluation used on honeycomb
structures ranging from ultrasonic transduction to various
lows frequency techniques. The focus, however, is given to
newly developed technique based onhysteresiseffectsinforce-
displacement curves. The area enclosed by the hysteresis loop
represents the amount of energy absorbed by the samples
during the loading and unloading phases. The great
advantage of this method is that it only requires access to one
surface of the structure to generate a force displacements
curve. A mechanical testing machine could take up to 15
minutes to produce a single force-displacement curve, this
method will produce the same curve in seconds. Much of this
research was devoted to the testing and development of the
techniques used to deduce a force-displacementcurvefrom an
accelerometer tap.
Keywords- Delamination, Micro cracking,
Thermography,Shearography,ComputerAided TapTest
1. INTRODUCTION
A honeycomb composite differs from a solid laminates in its
structure. The honeycomb composite makes use of a light
weight material fashioned into a honeycombsstructurewith
a high load bearing ability in relations to its weight. The
honeycomb is then sandwiched between two face sheets
which are solid laminates.Composites,unlikealuminum,can
have defects embedded within the material, ranging from
delamination between plies to micro cracks and porosity in
the matrix. Most cracks ins aluminums propagates to the
surface because they do not have to cross materials
interfaces, making them easily detectable. Cracks in
composites however are stopped by each ply interface,
making them much more difficult to detect. As a result,
structural uncertainties requires airplanes manufactures to
over design composites aircraft, taking away much of the
light weight advantages of the composite material. Non
destructive evaluation gives manufacturers the ability to
reducesor eliminates theoverdesignofcomposite materials,
allowing them to make full use of their lightweight
advantage. For this reason the development of non
destructive techniques is essential to the use of
composites within any structure. A focus on honeycomb
composites and their associated damages must be outlined
in ordered to evaluate the new detection techniques
developed throughout the course of this research. Various
different detection techniques havebeenaddressed, ranging
from the tap test to air coupled ultrasonic.
1.1 COMPOSITEs DEFECTS
1.1 Defects In The Laminate-In a composite structure,
the laminate constitutes a composition of materialsmade up
of fibers and resin matrix. Several plies are built up to form
the face sheets or laminate. The face sheet tends to be more
resilient to damages than the core, though damages cans
stills occur. Many times the damages cans occurs before the
structures has ever entered service. Poor layups conditions
ors flawed fabrications cans causes various types of defects
in the faces sheet. The majority of in-services damages ins
faces sheets comes from impacts damages, which cans
causes various defects within the layup, some of which
remains hidden to the naked eye.
1.2s Delamination-As delamination occurs when as gaps
forms betweens twos plies of deferent fiber orientation.
Dues to the facts that theses composites are usually
assembled ply bys ply, poor layups conditions cans be as
causes of delamination. Ifs manufacturingconditionsarenot
clean, unwanted particles, such as dust, cans be introduced
into the interfaces between the plies. Faulty bonding
conditions will result, which leads to as delamination. There
exist as resins rich areas which willsbelackinginfibers.This
sections is the weakest points of thetwosplyregionsand ass
as results becomes as failures points when the structure is
puts under as load.
1.3s Micro cracking-Insadditionstodelamination,matrix
micro cracking also presents itself ass as commons defects
ins solids laminates. It is ones of the many types of defects
associated with impacts damages, yet the damages cans be
caused by thermals cycling as well. This structures was
thermally cycled from rooms temperatures to cryogenics
temperatures several times to induces severe matrix micro
cracking.

2. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 07 | July 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 2112
1.4s Cracking Ors Buckling-Cracking ors buckling takes
places when as sandwiched composites is puts under an
excessive compressive load. When the loads exceeds the
limits of the structure, the cores buckles ands leaves as
fractures lines ins the cores which often takes the shapes of
as “smile” centered below the impacts site.
2. EXISTINGs INSPECTIONs METHODS
2.1s Ultrasonic Transduction
Ultrasonic transduction is as very popular techniques used
to inspects composites structures. It is able to detect
delamination, micros cracking, porosity, skin-to-cores
disbands, and as hosts of others defects commons among
composites materials. As selected frequency is dependents
upon the mediums used and the thickness of the material,
where lowers frequencies are able to penetrate further into
the material. Ultrasonic transductions is also hampered bys
very expensive ands complex scanning systems needed to
collects the data ands generates an image.
2.2s Thermography
Whiles ultrasonic makes uses of sounds waves propagating
though a material thermography makes uses of thermals
waves propagating from the surfaces into the material.
Theses waves are outsides the visible spectrums of light,
having longer wavelengths than those contained within the
visible spectrums of light. This sections wills outlines three
types of methods involvinginfraredsthermograph which are
actively beings used ass nondestructive techniques; they
include: Traditional Thermograph, Flash Thermograph ors
Thermal-Waves Imaging, ands Vibro Thermography.
2.3s Shearography-Another popular optical, non-contacts
methods is shearograpy; digitals speckles shearography is
starting to make its way into non destructive evaluation. Itis
an inter Ferro metric method which uses images obtained
from as structures whiles at rests and whiles loaded. When
the surfaces of the structures is illuminated by the laser, the
cameras produces twos sheared images which interferes
with each other producing as specklespattern.Theseimages
are obtained while the structure is at rest and loaded using
the same highs resolutions film, where the specklespatterns
wills changes whiles the structures is loaded. The twos
speckles patterns interferes with each other, revealing as
macroscopic fringes patterns which correlates to the
stiffness of the material.
2.4s Developments of Taps Test Method-Aside from
visual inspection, manual, hearing-based,taptestisarguably
the most practiced inspection technique on composites,
especially on bonded sandwich structures. s Because of its
wide use, as reals improvements of the taps tests methods
wills haves as significant impacts on the NDI(Non
Destructive Inspection)s of composites.
2.5s Computers AidedTapsTest-TheComputersAided
Taps Test (CATT)s is as methods which makes uses of an
accelerometers and electrics circuitstocapturestheimpacts
duration, τ, of the tap. The CATTs systems is able to stores
theses τ values and plots very informative contours maps
over the surfaces of the structure. Figs shows alls
components of the CATTs systems ass wells assanexamples
of as CATTs images produced on the computers screen. The
photos also shows as magnetic carts in the foreground,
which provides as quick, semi-automatic method of
obtaining alls the τs values over thesurfacesofthestructure.
s Figs 1.s As stiffness images of as Boeings 747s outboards
spoilers generated by taps test

3. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 07 | July 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 2113
Figs 2.s B747s outboards spoiler (left)s and its resulting
taps tests image(right).
2.6s Image-Based NDIs for Composite Inspection
Ultrasonic inspection, when implemented with mechanized
automated scanners generates scans images and is widely
used in the laboratories and for the inspections of
manufactured composites products. When used in the fields
ors ins as maintenances hangar, ultrasonic inspections is
typically carried outs with as flaws detector.Lowsfrequency
bonds testing and taps tests are not imaged-based
techniques. Ins the inspections of composites structures the
advantages of an image-based techniques cannot be over
emphasized Bys having the inspectionsresultspresented ins
an images forms as completes coverage of the inspected
areas is ensured.
As recently developed approach for makingsmanual,image-
based “C-scans” using ultrasound, eddy current, ands lows
frequency bondstesting(mechanicalsimpedancesanalysis)s
exploits the existences of off-the-shelf, lows cost,
commercials products with positions encodings capability.
The NDI output, such as the amplitude or time-of-flight ofan
ultrasonic signal, is combined with the position information
by software in the generation of the scan image.
3. CONCLUSIONS
As the use of composite increases, especially in the next
generation of airplanes, there will be a greater need for
nondestructive inspections procedures for quality’s
assurances by the manufacturers. The challenges wills
includes efficient inspections of thick primary structures’
Specifics fields inspections needs of the news generations of
composite-intensives airplanes may not arisesuntil theyare
ins services for as numbers of years. Mores bonded
structures are now classifieds ass primary structures and
wills receives more inspections attention. The uses of foam-
cored sandwiches are also on the rise, with the
accompanying NDIs needs. Theses twos techniques were
discussed ins detail, although no real developments were
made to theses techniques during the courses of the
research; they were simply used ass as reference.
REFERENCES
[1]s Baker, A.s Dutton, S.s Kelly, D.s (2004).s Composites
Materials for Aircrafts Structures. Americans Institutes of
Aeronautics and Astronautics, Inc.
[2]s Shull, B.E.s grey, J.N.s (1989).s X-Rays Measurements
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[3]sHsu,sD. (2006).Non destructive Evaluation ofDamagein
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[4]sKommareddy, V.s (2003).s Air-coupled ultrasonic
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[5]sNationals Instruments (2008).s Fundamentals of
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[6]s Kang, K.s Choi, M.s Kim, K.s Cha, Y.s Kang, Y.s Hong, D.s
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Cores Splice
Plys Drop-offs
Actuators fitting
Leadings Edge
Cores Splice

4. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 07 | July 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 2114
AUTHORS PROFILE
Sangita Kumari, M.tech Student at PM College
of Engineering, Sonipat , Haryana.
Er. Rahul Malik, completed B.Tech
(Mechanical Engineering) from Maharshi
Dayanand University, Rohtak in 2008 and
M.Tech. (Specialization: Design) from
Deenbandhu Chotu Ram University of
Science and Technology, Murthal Sonipat in 2011. Currently
working asanHeadofDepartment(Mechanical Engineering)
with PM College of Engineering, Sonipat, Haryana, India.