16

CHAPTER 2

LITERATURE REVIEW

2.1 LITERATURE SURVEY RELATED TO PRESENT WORK 17

2.2 SUMMARY OF LITERATURE REVIEW AND GAPS FOUND

TO ESTABLISH PRESENT WORK 38

BIBLIOGRAPHY 39

17

CHAPTER 2

LITERATURE REVIEW

The evolution of composite material has replaced most of the conventional

material of construction in automobile, aviation industry etc. Fibre reinforced

composites have been widely successful in hundreds of applications where there was

a need for high strength materials. There are thousands of custom formulations which

offer FRPs a wide variety of tensile and flexural strengths. When compared with

traditional materials such as metals, the combination of high strength and lower

weight has made FRP an extremely popular choice for improving a product’s design

and performance.

2.1 Literature Survey Related to Present Work

Polymer matrix composites are predominantly used for the aerospace industry,

but the decreasing price of carbon Fibres is widening the applications of these

composites to include the automobile, marine, sports, biomedical, construction, and

other industries [1]. Carbon Fibre polymer-matrix composites have started to be used

in automobiles mainly for saving weight for fuel economy. The so-called graphite car

employs carbon Fibre epoxy-matrix composites for body panels, structural members,

bumpers, wheels, drive shaft, engine components, and suspension systems. This car is

570 kg lighter than an equivalent vehicle made of steel. It weighs only 1250 kg

instead of the conventional 1800 kg for the average American car. Thermoplastic

composites with PEEK and polycarbonate (PC) matrices are finding use as spring

elements for car suspension systems [2]. An investigation was conducted by Issac M

Daniel et.al [3] on failure modes and criteria for their occurrence in composite

columns and beams. They found that the initiation of the various failure modes

depends on the material properties, geometric dimensions and type of loading. They

18

reported that the loading type or condition determines the state of stress throughout

the composite structure, which controls the location and mode of failure. The

appropriate failure criteria at any point of the structure account for the biaxiality or

triaxiality of the state of stress. Jeam Marc et.al [4] investigates the modeling of the

flexural behavior of all-thermoplastic composite structures with improved aesthetic

properties, manufactured by isothermal compression moulding. A four noded plate

element based on a refined higher order shear deformation theory is developed by

Topdar et.al [5] for the analysis of composite plates. This plate theory satisfies the

conditions of inter-laminar shear stress continuity and stress free top and bottom

surfaces of the plate. Moreover, the number of independent unknowns is the same as

that in the first order shear deformation theory. Banerji and Nirmal [6] reported an

increase in flexural strength of unidirectional carbon Fibre/ Poly(methyl

methacrylate), composite laminates having polyethylene Fibres plies at the lower face

Li and Xian [7] showed that the incorporation of a moderate amount of carbon Fibres

into ultra-high-modulus polyethylene (UHMPE) Fibres reinforced composites greatly

improved the compressive strength, flexural modulus while the addition of a small

amount of UHMPE Fibres into a carbon Fibre reinforced composite remarkably

enhanced the ductility with only a small decrease in compressive strength. Rohchoon

and Jang[8] studied the effect of stacking sequence on the flexural properties and

flexural failure modes of aramid-UHMPE hybrid composites. The flexural strength

depends upon the type of Fibres at the compressive face and dispersion extent of the

Fibres. Matteson and Crane [9] reported increase in flexural strength by using

unidirectional steel wire tapes in glass Fibre composites and carbon Fibres

composites. They showed that the increase in flexural strength was due to a change in

failure mode from compressive buckling to nearly ductile tensile failure. Bradley and

19

Harris [10] used unidirectional high carbon steel wires to improve the impact

properties of epoxy resin reinforced with unidirectional carbon Fibre reinforced.

Unfortunately, flexural design methodologies rely on their experimental

boundary conditions and the particular laminate setup, since a scaling of the results is

very difficult. The occurrence of usual failure modes under flexural loading

conditions, like delamination, matrix tensile fracture, localized compressive failure

and Fibre shear failure is strongly dependent of the material configuration (Fibre type,

resin type, lay-up, and thickness), the loading type. In this respect, three point bend

test equipment along with specimen indicated in figure 1 was used as a fast and cost

efficient comparison tool.

Jawad Kadhim Uleiwi [11]: Studies Investigated the effect of fibre volume fraction

on the flexural properties of the laminated composite constructed of different layers,

one of them having reinforced glass fibre and the other layer reinforced with Kevlar

fibre has been investigated experimentally and the results illustrate that tension stress

decreases with the increase in fibre volume fraction of glass fibre of the lower layer

while it increases with the increase of Kevlar volume fraction of the upper layer.

Wen-Pin Lin et.al [12]: Studies analysed the Failure of Fibre-Reinforced Composite

Laminates under Biaxial Tensile Loading. With the onset of failure for individual

lamina is determined by a mixed failure criterion composed of the maximum stress

criteria. It was observed that after the initial damage takes place, the response of the

lamina was described and observed to be brittle or degrading modes with the collapse

of the entire laminate.

Amjad J. Aref et.al [13]: Examined the structural behaviour of the fibre reinforced

polymer-concrete hybrid bridge superstructure system subjected to negative moment

flexural loads through experimental procedures. The experimental results showed that

20

the design of the hybrid FRP-concrete bridge superstructure under a negative flexural

moment is found to be stiffness- driven instead of strength-driven.

Slimane Metiche and Radhouane Masmoudi [14]:Studied the flexural behaviour of

light weight fibre reinforced polymer (FRP) poles. Experimental results show that the

use of low linear density glass-Fibres could provide an increase of the ultimate load

carrying capacity up to 38 % for some fibre reinforced polymer poles. It is also

observed that , the positioning of the hole in the compression side compared to the

tension side leads to an increase of the ultimate load carrying capacity up to 22 % for

the 5.4m (18 feet) fibre reinforced polymer poles and it was learnt that there was no

significant effect (3,5%) for the 12m (40 feet) fibre reinforced polymer poles. This is

mainly due to the stacking sequence and the stress states generated around the hole.

H. A. Rijsdijk et.al [15]: Investigated the influence of maleic-anhydride-modified

polypropylene (m-PP) on monotonic mechanical properties of continuous-glass-fibre-

reinforced polypropylene (PP) composites. This study showed an increase in

composite strength as a result of the addition of maleic-anhydride- modified PP to

continuous-glass-fibre-reinforced PP composites. An optimum in both longitudinal

and transverse flexural strength was reached for composites based on a PP matrix

with 10wt% m-PP.

P.N.B. Reis et.al [16]: Studied the flexural behaviour of hand manufactured hybrid

laminated composites with a hemp natural fibre/polypropylene core and two glass

fibres/polypropylene surface layers at each side of the specimen. Laminate composites

(LC) present an ultimate strength about 4% higher than the hybrid laminated

composites (HLC) associated to changes in failure mechanisms, while the stiffness

modulus was also about 3.8% higher. Fatigue strength of hybrid laminated composites

21

is also about 20% lower than the laminated composites as consequence of the change

of the failure mechanisms and of the different static strengths.

M. Davallo et.al [17]: Investigated the Mechanical behaviour of unidirectional glass-

polyester composites to identify performance differences of composites with different

glass lay-ups and laminate thicknesses during flexure and tensile testing formed by

hand lay-up moulding (HLU). es. The damage generated in the composites exhibited

matrix cracking on the lower face followed by the coalescence of delaminations

formed within the reinforcing plies.

Michel Espinosa Klymus et.al [18]: Evaluated the fracture pattern of four

composites for indirect dental restoration relating to three-point flexural strength.

Further the compressive strength and modulus of elasticity were also addressed.

Composites polymerized under high temperatures (belle Glass and Targis) had higher

flexural strength and elastic modulus values than composites polymerized by light

temperatures (Artglass and Solidex). It was found that they failed earlier under

compression because they were more rigid and showed partial fracture in the material

bulk.

S. Benjamin Lazarus et.al [19]: Investigated the mechanical properties of natural

Fibre developed using a plant fibre which is used for green manuring called Sunhemp.

Polyester is used as the matrix to prepare the composite. From the results the

applications of the composite for some specific purposes can be decided upon since

the maximum value of strength is achieved for a particular Fibre length and Fibre

weight ratio.

M. Wesolowski et.al [20]: Studied the elastic properties of laminated composites by

different Non-Destructive techniques. Two carbon fibre XP45 Turane Resin

laminated composite plates and four beams cut from the plates along their principal

22

directions 1, 2 (two beams from each plate), are chosen for the study. Among all

proposed methods for the elastic properties characterization, the approach based on

the inverse technique is most suited for the convenient, fast, and accurate

identification of elastic properties.

J. Davies and H. Hamada [21]: Investigated the flexural properties of hybrid

unidirectional fibre reinforced polymer (FRP) composites containing a mixture of

carbon (C) and silicon carbide (SiC) fibres were evaluated at span to depth (S/d) ratios

of 16, 32, and 64. The hybrid composite flexural strength was generally higher than

either the pure CFRP or SiC fibre composites. The work of fracture was a factor of

2.6 larger for the S 4 /C 4 specimen compared to the S specimen and suggests that

these hybrid FRP composites may have a role as energy absorption materials. The

compressive stress, compressive strain and modulus to failure of the SiC fibre were

estimated to be 3.46 GPa, 157 GPa, and 0.018, respectively. Most of the specimens

exhibited out-of-plane pairs of conjugate kinks although specimens with larger SiC

fibre were more inclined to show evidence of shear failure.

IH Tacir et.al [22]: Studied the reinforcing effect of glass fibres on the fracture

resistance and flexural strength of acrylic resins. In this study, statistically significant

differences were found in the flexural strength of the specimens. The injection-

moulded, fibre reinforced polymers had significantly lower flexural strength than the

injection-moulded composites, and the microwave-moulded, fibre reinforced

composites had lower flexural strength than the microwave-moulded composites. The

fracture resistance was significantly higher in the injection moulded, fibre-reinforced

composites than in the injection-moulded composites, and the fracture resistance was

significantly higher in the microwave moulded, fibre-reinforced composites, than in

the microwave-moulded composites.

23

Hoo Tien Kuan et.al [23]: Evaluated the mechanical properties of composite

materials based on two types of self-reinforced polypropylene (SRPP) and a glass

fibre reinforced polypropylene are investigated under quasi-static and dynamic

loading conditions. Hybrid laminates based on glass fibre reinforced polypropylene

skins and a self-reinforced polypropylene core was manufactured using a

compression moulding technique. Hybridising the glass and polypropylene fibre

composites in this manner combines the strength and stiffness of the glass fibres

system with the excellent impact resistance and low density of the self-reinforced

polypropylene composite. Tests have shown that increasing the volume fraction of

self-reinforced polypropylene can enhance the energy-absorbing characteristics of the

hybrid composites. Further with the increase in the amount of glass fibre in the

reinforced composite there was an increase in the flexural modulus of the hybrid

composites.

M. Davallo et.al [24]: Flexural properties of continuous random glass-polyester

composites formed by resin transfer moulding (RTM) and hand-lay up (HLU)

moulding have been studied to determine the effects of glass content, composite

thickness, reinforcement geometry and type of fabrication on damage developed

during flexure tests. Strain values both at maximum-load and failure were determined.

The failure strains of the two sets of composite series were relatively constant. Hence,

both types of composite series appeared to fail at a critical strain value. The damage

developed during the test was monitored on the side of each polished beam using an

optical microscope.

S. Tolson and N. Zasara [25]: Investigated the computational model for determining

the ultimate strength of an arbitrary laminated composite plate. A new higher order

shear deformation plate theory was developed. The theory utilizes seven degrees of

24

freedom at each node. An improvement in the accuracy of the transverse shear stress

was obtained by calculating these stresses using three-dimensional elasticity

equilibrium equations. The composite failure analysis is used to determine the first

and last ply failure of a laminated composite plate. The computer programming was

developed based on the seven degree of freedom higher order shear deformation plate

theory.

Geon-Woong Lee et.al [26]:Studied the mechanical properties and failure

mechanisms of through-the-thickness stitched plain weave glass fabric/polyurethane

foam/epoxy composites. Hybrid composites were fabricated using resin infusion

process (RIP). Stitched sandwich composite increased drastically the flexural

properties as compared with the unstitched fabrics. Breaking of stitching in yarns was

observed during the flexural test and thus the failure mode yielded relatively high

flexural properties. Polymer composites with stitched sandwich structure improved

the mechanical properties with increasing the number of stitching yarns. It was

concluded from the study that proper combination of stitching density and types of

stitching fibre is important factor for through-the-thickness stitched composite panels.

N.K. Naik et.al [27]: Investigated the inter laminar shear behaviour of typical

polymer matrix composites under high strain rate shear loading. Tensional split

Hopkinson bar (TSHB) apparatus is used for the studies in the shear strain rate range

of 496–1000/ s. It is observed that the interlaminar shear strength at high strain rate is

enhanced compared with that at quasistatic loading. Further, it is observed that the

inter laminar shear strength increases with increasing shear strain rate within the range

of shear strain rate considered.

Slavisa Putic et.al [28]: This paper outlines the experimental investigation of inter

laminar shear strength as the critical mechanical property of composite constructions

25

of structure elements Placed between two thin glass mat layers where a layer is placed

on the glass fabric of the same structure but of different density, with different

polyester resin matrices. The significance of the shear strength lies in the fact that for

all types of composites it is strongly influenced by factors weakening the interface

binds.

W.Richards Thissels et.al [29]: The IM6 Fibres 3051/6 epoxy resin showed a 40%

increased in stress –strain slope under compression loading at strain rate of 2000 L/S

than 1×10-3 L/S when the applied load was parallel,450 and normal to the Fibre axis.

The compression test showed that delamination significant failure component. The

applicability of current hole in plate analytical methods to highly anisotropic material

is there questionable. Both hole in a plate analytical methods indicates that GI is about

50% higher than G1.

Jane Maria Faulstich de Paiva [30]: This paper shows a study involving mechanical

(flexural, shear, tensile and compressive tests) and morphological characterizations of

four different laminates based on 2 epoxy resin systems (8552TM and F584TM). The

results show that the F584-epoxy matrix laminates present better mechanical

properties in the tensile and compressive tests than 8552 composites. Further it is

observed that PW laminates for both matrices show better flexural and inter laminar

shear properties.

Roberto J. Cano and Marvin B. Dow [31]: In this study, the unidirectional laminate

strengths and moduli, of notched (open-hole) and un notched specimens in tension

and Compression tests were performed and the properties of quasi isotropic polymer

composite laminates, and compression after impact strengths of five carbon fibre /

toughened matrix composites, IMT/E7T1-2, IMT/X1845, G40-800X/5255-3,

IM7/5255-3, and 1M7/5260, have been evaluated. This investigation found that all

26

five materials were stronger and more impact damage tolerant than more brittle

carbon/epoxy composite materials currently used in aircraft structures.

José Ricardo Tarpani [32]: Quasi-static tensile properties of four aeronautical grade

carbon-epoxy polymer composite laminates, in both as-received and pre-fatigued

states, were determined and compared. The materials also displayed a significant

tenacification (toughening) after exposed to cyclic loading, resulting from the

increased stress (the so-called wear-in phenomenon) and/or strain at the maximum

load capacity of the specimens. Two-dimensional woven textile (fabric) pre-forms

fractured catastrophically under identical cyclic loading conditions imposed to the

fibre architecture, hence this prevents their residual properties from being

determined.

Wen, H.W., Reddy, T. Y., Reid, S. R. and Soden, P. D [33]: Conducted

experiments on composite sandwich panels consisting of woven E-glass/polyester

laminates and foam core and also found that there was an increase in the failure load

of the composite sandwich under impact loading when compared to static load

indentation. They attributed the load increase to the enhanced strength and stiffness of

the glass/polyester face sheet and foam core at high strain rates as well as the inertia

of the projectile and composite sandwich. Layered materials and sandwich structures

have diverse and technologically interesting applications. These include the increased

use of composite laminates in aerospace and automotive engineering.

Hutchinson, J.W, Suo Z, Rajapakse, Y.D.S Valenti, M [34,35,36]:The introduction

of layered concrete pavements in civil engineering, the use of thin films and layered

structures in micro-electronic components, and very recently, the introduction of

sandwich structures in a variety of aerospace, naval, automotive engineering

applications. In an entirely different length scale such materials and structures are also

27

found in the natural layered rock structure of earth’s crust. The failure characteristics

of layered materials and sandwich structures subjected to static loading have been

investigated extensively in the past years and their dynamic counterparts have

remained elusive.

C.T., Rechak, S, Much & Cantwell, W.J., Morton, [37,38]: Work have been

addressed to identify the evolution of failure modes for different loading regimes, it is

convenient to first classify these modes based on the material constitutions of

layered/reinforced structures. There are two major categories of failure observed in

post-mortem studies. The first major failure category is de cohesion (or cracking)

between bonded layers at an interface. This is often referred to as de lamination in

composite laminates or interfacial de bonding in thin films or sandwich structures. It

is also called inter-layer failure. In general there are two distinct inter-layer failure

modes observed. The first one involves opening-dominated inter-layer cracking or

‘‘de lamination buckling’’

Wu, H.T., Springer, G.S, Lambros, J., Rosakis, A.J et. al, [39,40]: Polymer

laminate composites involves shear-dominated inter-layer cracks or shear de

laminations, and often occurs in layered materials subjected to out-of-plane impact

was observed, present study described the failure modes by conducting a series of

experiments on dynamic de lamination of thick Fibre reinforced composite laminates.

S.M.R. Khalilia, A. Shokuhfar[41]: Effect of some important parameters on low-

velocity impact response of the active thin-Layered/walled hybrid composite plates

embedded with the shape memory alloy (SMA) wires was investigated. shape

memory alloy wires were embedded within the layers of the composite laminate. The

effect of the shape memory alloy wires on contact force, deflection, in-plane strains

and stresses of the structure was analyzed. The first-order shear deformation theory as

28

well as the Fourier series method was utilized to solve the governing equations of the

composite plate analytically. Further the interaction between the impactor and the

plate was modeled with the help of two degrees-of-freedom system, consisting of

springs-mass system. The Lambros linearized Hertzian contact model was used in the

impact analysis of the laminated hybrid composite plate. Results indicated that some

of the important geometrical and physical parameters like the shape memory alloy

volume fraction, orientation of composite Fibres, impactor mass, impactor velocity,

and a/h ratioof the specimen that is length-to-thickness ratio of the plate are important

factors affecting the impact process and the design of the structures.

P. H. Bull et.al [42]: An investigation of the response of sandwich structures

subjected to impact velocities of virtually 0 m/s and approximately 1000 m/s was The

higher velocity exceeds both the longitudinal and the transverse wave propagation

velocities of the core material in the sandwich panels. Their objective was to

investigate the possibility to simulate the damage from ballistic impact of sandwich

panels through quasi-static experiments. Residual strength of impacted panels is

analyzed by finite element analysis.

Per Wennhage [43]: A generic model of a railway car body in sandwich design was

weight optimized subject to various constraints. The constraints were global natural

frequency, buckling and wrinkling, and sound reduction constraints. Finite element

model was used for global natural frequency analysis, while sandwich plate theory

was used for local structural analyses. The acoustic environment is an important

factor in vehicle design, and a sandwich construction may have poor ability to

attenuate air-borne sound, i.e., have a low sound reduction index. The sound reduction

index is affected by the dimensions and materials in the sandwich. By careful design,

29

the sound reduction can be improved, while maintaining the light weight properties of

the sandwich design.

Kardomateas. [44]: A nonlinear solution method was developed for buckling and

post-buckling of elliptical de laminations under compressive loads. This method

employs a series solution approach in conjunction with the perturbation technique to

solve the laminated plate equations for large deflections. Experiments were performed

on sandwich panels containing delaminated face-sheets (the de laminations were in

between layers of the face-sheet; the face-sheet/core interface did not contain de

laminations). The nonlinear models were able to predict the onset of de lamination

and failure loads in the experiments.

Liang tseng et.al [45]: An integrated sandwich composite adopting 3D woven fabrics

as the core material was experimentally characterized for its effective elastic modulus

as well as its capacity of receiving impact energy. A series of unidirectional tensile

tests as well as impact experiments were conducted for the sandwich composite

fabricated using two different types of reinforced lamina as the face-sheets.

G. Zhou, M. Hill, J. Loughlan [46]: Damage characteristics of composite-skinned

honeycomb sandwich panels in bending (flexural) were investigated, with both

hemispherical (HS) and flat-ended (FE) indenters. The skin thickness of the cross-ply

is varied from 8 plies to 16 plies, whereas the density of the 12.7 mm thick aluminum

honeycomb core varies from 50 to 70 kg/m3. Panels were loaded quasi-statically and

are clamped in 100-mm testing area are subjected to either bending or on a rigid

base.

Whitney, J.M. and Browning, C.E [47]: The effects of varying these parameters on

damage mechanisms are examined through response curves as well as cross sections

30

of selected specimens. Short-beam shear tests for determination of the ILS strength

were conducted.

Bernard, M.L. and Lagace, P.A, Williamson, J.E. and Lagace, P.A [48,49]:

showed that the moderate thickness effect on the ILS strength is negligible and in fact

laminates with fewer plies have slightly higher ILS strength than laminates with more

plies.

U. K. Vaidya, C. Ulven, S. Pillay and H. Ricks [50]:Therefore the value obtained

for the 16-ply laminate was taken as a low-bound approximation for the other

laminates. Lagace and coworkers [conducted a series of quasi-static and low-velocity

impact tests on square composite panels as well as wide composite beams with both

aluminum and nomex honeycomb cores with a hemispherical (HS) indenter/

impactor. considered filling of honeycomb type cores with foam to produce sandwich

constructions. The potential benefits of this approach are enhancement of damage

resistance, and ability to process honeycomb type sandwich structures through cost-

effective vacuum assisted resin transfer molding (VARTM). Two cores are

considered, a polyurethane foam for full filling of honeycomb cells, and syntactic

foam for partial filling, in conjunction with carbon–epoxy face sheets. Their impact

response was investigated under low and high velocity impact (LVI and HVI

respectively).

Hiroshi and Isao [51]: Investigated the evolution of damage behavior considering the

moisture (water) absorption effect on the textile structures. Non destructive method,

that is direct visual observation method was adopted to investigate the damage

observation. The materials investigated were plain woven fabric and multi axial

knitted fabric. Carbon Fibre reinforced laminates of plain woven did not exhibit much

lower performance under compression after impact. On the other hand the properties

31

of the water absorbed multi- axial knitted fabric properties decreased drastically when

compared with the dry ones. Water absorption did not alter the strength and had no

effect on the compression after impact strength. There were traces of deterioration

caused due to water absorption in both plain woven and multi axial carbon Fibre

reinforced laminates.

Toshio ogasawara and Tet suoka Sai [52]:Investigated the influence of fullerenes

dispersion on the carbon –Fibre reinforced epoxy matrix for its mechanical properties.

The various mechanical properties like flexural test and short beam shear strength

were conducted and it was observed that by dispersing of fullerenes into the matrix

there was an increase in the mechanical properties.The inter laminar fracture

toughness was enhanced by 60%. The small amount of fullerenes will increase the

failure strain of epoxy resin and in turn improves the carbon Fibre reinforced polymer

strength.

F.Elgabbas et.al. [53]: Conducted experimental investigation on the structural

behavior of precast reinforced hallow concrete slabs subjected to flexural loads. For

the analysis externally bonded laminates with near surface mounted are used. Near

surface mounted technique resulted in optimum strength. Near surface mounted

flexural strengthening needs to be carefully designed to avoid shear failure. Pre

mature de bonding was observed because of externally bonded technique.

Kolesnikov et. al,[54]: Investigated the effect of joining structural composites for

aerospace applications. Structural joining enhances the disturbance in the optimized

structure and results in increase in overall weight of the structure and results in

increase in over all weight of the structure. The potential of the light weight

composite materials made of carbon Fibre reinforced polymers are affected because

of these joining and fastening capabilities. The titanium layers are embedded at these

32

joints where fastening and bolting is done which resulted in improvement in structural

efficiency. Hence this demonstrates the influence of titanium hybridization with the

carbon Fibre reinforced polymer materials and results shows advantages of this

hybridization.

Alaattin Aktas and Ibrahim uzun[55]: Investigated the influence of sea water on

the woven glass Fibre laminated composites for its strength. The experiments were

carried by varying the edge distance and the pin diameter. The ratio of width and pin

diameter was varied during the experiments. The failure modes were studied for

varied period of immersion and depths.

B. Pradan and S.K.panda[56]: Studied the effect of residual stresses and mechanical

loading on the ply lay up composites. Inter laminar de lamination crack growth

behavior was analyzed in this paper. Finite element analysis has been performed to

understand the inter laminar elliptical de lamination behavior which is mainly due to

the manufacturing defects and the other reasons for this type of de lamination was

analyzed which may be due to symmetric mid plane quasi - isotropic Fibre reinforced

polymer composite layup. Strain energy release rate procedures were employed to

analyze de lamination and crack growth at the inter faces. It was observed that the ply

sequence and orientation plays a important role in this aspects.

J.Lee and C.Soutis[57]: Investigated the influence of thickness on the compressive

behavior of the laminated composites with different stacking sequence with a open

hole at the centre. It was observed that the strength of the specimen with increasing

thickness was increased. Measured failures strength were compared with the predicted

values.

S.Kellaas, J.Morton and P.T.Curtis[58]: Studied the uni axial strength of centre –

notched laminates under hygro thermal environment. The laminates investigated were

33

carbon Fibre reinforced epoxy laminates. Dry and wet specimens were tested for

tension and compression strengths in a varying range of temperatures. The fabrication

was done on two kinds of stacking sequences. The diameters of the holes were varied

and tensile and compression strengths measured and damage response was observed.

It was found that the interactions depend on the stacking sequence and notch

geometry.

M.Raghavendra et. al,[59]: Investigated studies on woven glass Fibre reinforced

polymer matrix and determined the tensile strength, compressive strength and in plane

shear strength at room temperatures and at high temperatures and at high

temperatures. The test data is statistically analyzed it was found that the specimens at

higher temperatures showed low strength when compared with the specimens at room

temperature.

Buket Okutan[60]: Conducted experimental studies to determine strength of

mechanically fastened Fibre – reinforced E-glass/epoxy composites. Various

Mechanical properties and strength was determined experimentally. The laminates

manufactured had different orientations of the Fibres. Parametric study was conducted

considering the geometry of the Fibre orientation and failure characteristics for the

pin-loaded Fibre reinforced laminated composites were analyzed. A comparison

between experimental values with finite element modal was carried. It was observed

that the ply orientation and the geometry of the composites are crucial in case of

pinned Fibre reinforced laminated composites.

Adam Quiter[61]: Aerospace structures are often prone to flexural loads, that may

lead to result in serious damage. Hence, for structural integrity, aerospace structures

must be efficient to resist bending. The first use of modern composite materials in

commercial aircrafts was by Airbus in 1983.

34

Pegoretti, E. Fabbri, C. Migliaresi, F. Pilati [62]: Flexural loading causes stresses

in the polymer laminated composites that may vary through the thickness. These

flexural stresses are the maximum at the outer surfaces and are minimum (zero) in the

middle at the neutral axis. In the laminates subjected to pure bending, the composite

failure initiates on either the tensile or compressive side depending upon whether the

composite is stronger in compression or tension respectively. The stress in an

individual ply depends upon the stiffness of that ply and its distance from the

laminate’s neutral axis. By including, one or more extra components having relatively

better elastic properties in the laminate can help in improving the flexural properties

of the composite structures. This class of composite materials consisting of more than

two types of constituents is commonly known as a hybrid composite.

G.Kertsis[63]: Hybrid composites having two or more types of reinforcing Fibres in

a polymer matrix can be classified according to the way their constituent Fibres are

mixed such as; sandwich hybrids, interply hybrids, and intermittently mixed hybrid

composites. Interply hybrid composites are gaining attention because hybridization

facilitates the tailoring of mechanical properties according to need by having a

selective amount of extra reinforcement at some selective position in the laminate.

presented a comprehensive review on the properties of hybrid composites. The

relative volume fraction of reinforcing Fibres and their positioning in the hybrid layup

act as the determining factors in the enhancement of flexural properties. Therefore, for

structural laminates under flexural loading, material can be designed for better

flexural properties by investigating the effect of the stacking sequence.

Banerji and Nirmal [64]: In a hybrid composite, the two reinforcing Fibres differ in

their mechanical properties and the interface they make with the matrix it was

observed that there was an increase in flexural strength of unidirectional carbon Fibre/

35

Poly(methyl methacrylate), composite laminates having polyethylene Fibres plies at

the lower face.

Li and Xian [65]: Showed that the incorporation of a moderate amount of carbon

Fibres into ultra-high-modulus polyethylene (UHMPE) Fibres reinforced composites

greatly improved the compressive strength, flexural modulus while the addition of a

small amount of UHMPE Fibres into a carbon Fibre reinforced composite remarkably

enhanced the ductility with only a small decrease in compressive strength.

Rohchoon and Jang [66]:studied the effect of stacking sequence on the flexural

properties and flexural failure modes of aramid-UHMPE hybrid composites. The

flexural strength depends upon the type of Fibres at the compressive face and

dispersion extent of the Fibres.

Matteson and Crane [67]: Reported increase in flexural strength by using

unidirectional steel wire tapes in glass Fibre composites and carbon Fibres

composites. They showed that the increase in flexural strength was due to a change in

failure mode from compressive buckling to nearly ductile tensile failure.

Bradley and Harris [68]: Used unidirectional high carbon steel wires to improve the

impact properties of epoxy resin reinforced with unidirectional carbon Fibre

reinforced laminate. By having steel wire on the compression side of the specimen,

the strength of the laminate got enhanced, thus increasing the energy of the fracture,

increased by 200% by elimination of compressive failure mode. The flexural strength

of the hybrid laminate was increased particularly when the wires were placed in the

compression side of the specimen and also as the volume fraction of the wire was

increased.

Zuoguang et.al [69]: Damage characteristics of composite sandwich panels in

bending were investigated with both hemispherical and flat-ended indenters. The

36

thickness of the cross-ply laminate skins varies from 8 to 16 plies. Clamped panels

with a 100-mm testing area are loaded quasi-statically in bending. The effects of

varying these parameters on damage mechanisms were examined through response

curves as well as cross sections of selected specimens.

Issac M Daniel et.al [70]: An investigation was conducted on failure modes and

criteria for their occurrence in composite columns and beams. They found that the

initiation of the various failure modes depends on the material properties, geometric

dimensions and type of loading. They reported that the loading type or condition

determines the state of stress throughout the composite structure, which controls the

mode of failure and its location. The appropriate failure criteria at any point of the

structure account for the bi axiality or tri axiality of the state of stress.

Jean Marc et.al [71]: Investigates the modeling of the flexural behavior of all-

thermoplastic sandwich composite structures with improved aesthetic properties. The

aesthetic thermoplastic sandwich composites exhibit specific features such as thick

multi-layered faces and significant core properties variation due to processing

conditions. Taking into Consideration these specific features, a three-step calculation

methodology, they developed an accurate analytic model. With the help of the

analytical model developed the equivalent shear properties of the core after

manufacturing was predicted and to take into account the influence of the glass veil

layer used to improve the surface quality of the part.

Topdar et.al [72]: A four node plate element based on a refined higher order shear

deformation theory is developed, for the analysis of composite plates. This composite

plate theory satisfies the conditions of inter-laminar shear stress continuity and stress

free top and bottom surfaces of the plate. Further, the number of independent

unknowns is the same as that in the first order shear deformation theory. Numerical

37

examples of composite plates were solved to validate the element & results are

presented.

Mallick P.K [73]: Polymer matrix composites are predominantly used for the

aerospace industry, but the decreasing price of carbon Fibres is widening the

applications of these composites to include the automobile, marine, sports,

biomedical, construction, and other industries.

Gill, R.M [74]: Carbon Fibre polymer-matrix composites have started to be used in

automobiles mainly for saving weight for fuel economy. The so-called graphite car

employs carbon Fibre epoxy-matrix composites for body panels, structural members,

bumpers, wheels, drive shaft, engine components, and suspension systems. This car is

570 kg lighter than an equivalent vehicle made of steel. It weighs only 1250 kg

instead of the conventional 1800 kg for the average American car. Thermoplastic

composites with PEEK and polycarbonate (PC) matrices are finding use as spring

elements for car suspension systems.

Y.C.Shiah et.al [75]: Investigated an integrated sandwich composite adopting 3-D

woven fabrics as the core material & thoroughly studied its elastic modulus. Even

with extensive applications of 3-D woven sandwich composites due to their improved

mechanical properties, there is no suitable theoretical model that has been proposed to

predict the elastic modulus for such composite structures in the open literature so far.

In this work, a theoretical model by means of a micro mechanics approach and the

rule of mixtures is proposed to predict its effective in-plane elastic modulus. To verify

the veracity of their prediction, unidirectional tensile tests were also carried out to

determine the effective elastic modulus. Eventually, their experimental results turn out

to agree with predicted values.

38

2.2 SUMMARY OF LITERATURE REVIEW AND GAPS FOUND TO

ESTABLISH PRESENT WORK:

After exhaustive literature survey and discussion, it is imperative that the use

of polymer laminated composites is an emerging field in all sectors of the industry

specifically in automotive industries because of its benefits of high strength to weight

ratio in order to enhance performance of the vehicle. Evaluation of Flexural and Shear

properties of laminated composites are realised to be important as flexural test and

short beam shear test are considered as real time tests as most of the components are

subjected to bending and shear load.

1. Flexural and Short beam shear properties for plain bi-woven laminates were

not much emphasised for different fibre orientation in the earlier literature.

2. Flexural properties for varying thickness of the specimens were not being

evaluated especially for fibre reinforcement volume between 54-60 % in the

earlier literature.

3. Effect of de-lamination at the interface between the matrix and Fibre

reinforcement under flexural loads is not being addressed.

4. Not much of the work has been done on correlation of experimental results

with FEA results for different fibre fraction and fibre orientation.

So, in the present work, it is intended to focus the Investigation on flexural and

shear properties of the laminated composite materials which is very useful to the

industry and helps design engineers to choose appropriate materials for specific

applications.

39

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