Polymer International Polym Int 53:1274–1281 (2004)DOI: 10.1002/pi.1511

Impact response of epoxy systems containingshort fibres and/or oxide particles asreinforcementsKishore,1∗ SP Harimkar2 and DS Desai31Polymer Composites Laboratory, Department of Metallurgy, Indian Institute of Science, Bangalore 560012, India2TVS Motors Ltd, Mysore 571311, India3Wilco International Systems Pvt Ltd, Hyderabad 500082, India

Abstract: This work looks at the role played by constant levels of fibre and/or particles in epoxy matriceson impact responses during dynamic loading. In order to delineate the differing roles of reinforcements,hybrid composites containing different amounts of fibres and particles were prepared. Maximum loadsand energies were used to distinguish the responses during and following impact. Scanning electronmicroscopy (SEM) was used to characterize the surface features before and after failure. Furthermore,such microscopic analyses were also employed to substantiate the deductions arrived at based onmechanical data analysis, which included the deduced parameter in the form of energy for propagation.The experimental results pointed to the fact that the total energy and load generally rise as the fibrecontent in the epoxy system increases. The hybrids, on the other hand, displayed a trend where thenormalized load and the total energy increased as the fibre content in the hybrid was raised from 1 to 5vol%. This was most evident when the differing levels of fillers and fibres were fixed at a total of 7 vol%. Inaddition, comparison was made between two sets of compositions of fibres and particles in the composites.The results showed that the higher fibre content in the hybrid allowed greater load bearing and energyabsorption and the difference in recorded levels increased with higher fibre content in one hybrid set.Fractography studies indicated flatter surface features for systems with only particles added, whereas the‘all-fibre’ bearing systems displayed ‘fast-fracture’ features resembling ‘river patterns’. 2004 Society of Chemical Industry

Keywords: short fibers; oxide particles; hybrids; impact; fractography

INTRODUCTIONThe search for materials which cater to greaterdemands in performance and reliability has led topolymer composites. These composites are oftenreinforced with ‘capital-intensive’ fibrous materialthat is expensive but is, performance-wise, highlyreliable. Automobile, sports goods and furniture-based industries use such materials.1–6 The strengthretention following impact to such materials is asubject of considerable concern to a wide range ofengineering disciplines and spectrum of industries.Generally, thermoset matrices are preferred whengreater emphases on durability and long service arerequired. Among the thermosets, epoxy resins areconsidered important as they possess several attractiveproperties for use with many fibrous reinforcements.

As regards the epoxies, the anhydride-curedmaterials show better impact properties as the alkenylchain length of the hardener increases.7 The explana-tion offered for this observation is that the non-polar

component of the alkenyl succinic anhydride favoursimprovements in the toughness properties.7 The frac-ture behaviours of four epoxy resins under impactconditions have been examined by D’Almeida.8 Theadiabatic test conditions and the temperature increasethat follows were suggested as favouring bluntingof the crack tip and hence the energy absorption.8

In another work, the same author prepared com-pounds of the difunctional liquid epoxy diglycidylether of bisphenol–A (DGEBA) with an aliphaticamine and two aromatic polyamines,9 and a rela-tionship between the impact energy absorbed and thetemperature rise was established.9 To study the influ-ence of resin/hardener ratio on the impact behavior ofthe epoxy system, the resin was crosslinked with differ-ent amounts of triethylene tetramine hardener.10 Thetests showed a continuous increase in the absorbedenergy with increase in hardener/resin ratio.10 Boththe synthesis and the impact properties of the silox-ane–DGEBA epoxy copolymer were investigated by

∗ Correspondence to: Dr Kishore, Polymer Composites Laboratory, Department of Metallurgy, Indian Institute of Science, Bangalore9560012, IndiaE-mail: balkis@metalrg.iisc.ernet.in(Received 28 March 2003; revised version received 8 September 2003; accepted 10 November 2003)Published online 1 June 2004

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Lin and Hung.11 The impact strengths recorded anincrease and this was related to the structure and con-tent of siloxane oligomers in the copolymer.11 Theseauthors further observed on impact specimens a roughsurface for the copolymers and smoother surfacesfor the unmodified epoxy resins. The morphologicalchanges indicated that siloxane acted as a toughen-ing agent in the epoxy network, thereby contributingto improvement in the impact properties.11 The lit-erature shows studies of the effects of both angularsilica particle12 and glass fibres13 on the impact prop-erties of epoxy resins and thermoplastic resin systems.Efforts to lessen the damage in such materials byinclusion of wood chips,14 rubber15 glass fibres16–18

have also been made. It was noticed that the compos-ite impact strength increased directly with increasingfiller concentrations.

A cursory glance at the literature shows that, by andlarge, the emphasis has been on polymers reinforcedwith fillers in one instance and fibres in the other.For the former category, the work of Hussain et al,concerning the study of fracture behavior and fracturetoughness of the TiO2 –epoxy filled system, may bementioned.19 For larger particle sizes and at lowertesting temperatures, the fracture toughness was foundto increase.19 Wang et al reported the combined effectof SiO2 and the interfacial region between the fillerand matrix of an epoxy resin20 on the yield strength ofthe system. Particle addition to the matrix was foundto produce large disturbances in the stress distributionleading to stress concentrations, which were foundto have negative effects on the yield strength ofthe composite.20 In another study, the effect ofthe coupling agent in the TiO2-reinforced systemhas been examined.21 The Young’s modulus andflexural strength of titanate-coupling-agent-treatedcomposites were significantly improved over silane-treated systems.21 The simultaneous inclusion ofAl2O3 filler and carbon fibre in epoxies forms thesubject matter of another investigation by Hussainet al, where they found that the mechanical propertiesimprove by incorporating 10 vol% of nano- or micro-sized particles into the epoxy matrix.22

As regards the carbon-filament-reinforced system inepoxies, this showed an increase in both longitudinaland transverse loss moduli while the storage moduluswas found to decrease in the longitudinal direction.23 Afurther study of the influence of chopped Kevlar fibreson the energy dissipation process showed that differentfailure mechanisms were involved in the dynamic andquasi-static delamination processes.24 G� values werefound to essentially double due to inclusion of smallamounts of Kevlar fibre.24 When the experiments wereextended to microscopic, investigations the resultsshowed support for processes such as fibre bridging,‘pull out’ and fracture of the chopped Kevlar fibresduring delamination.24 While quite a number ofstudies have been carried out on either fibre- orparticle-reinforced systems,12–18 composites with bothparticulate and fibre reinforcements have been studied

only rarely.22,24,25 It is also clear from perusal of theliterature that epoxy systems reinforced with hybrid(ie differently shaped) fillers have been little exploredand hence there is a need to explore this aspect.This present effort, therefore, addresses such issuesby selecting an inexpensive mineral and short-lengthglass fibres to reinforce an epoxy material, while at thesame time keeping low-end applications in mind.

Corderite, an inexpensive mineral, consisting ofsmall spherical particles of assorted sizes was chosenas the filler material. This mainly consists of silicaand alumina and when bonded well at the interfacewith a matrix, confers good mechanical properties. Asurvey of the available literature revealed no referenceto work having been carried out with this particularfiller system. In order to differentiate the roles of thefibres and the particles, which differ considerably intheir aspect ratios, at one end only fibre-bearing epoxycomposites have been examined while at the other,only mineral particle bearing composites have beeninvestigated. To make this comparison substantive,the percentage volume level of the reinforcements waskept the same in both cases. The scope of the workwas broadened by studying systems where both fibresand oxide particulates were present simultaneously invarying proportions such that the total volume wasmaintained at the same level as that employed formaking composites with only particulates as fillers.The purpose of including both reinforcements in thesame composite system was to study the responsechanges resulting primarily from the aspect ratioand surface area of contact differences arising whileusing regularly shaped glass fibres in one situationand irregular surface bearing oxide particulates inthe other. The properties chosen to evaluate weredata such as maximum load, energy, etc. gatheredby the instrumented impact set-up employed for thispurpose. In addition, the failure modes exhibitedby the reinforcement-bearing systems were examinedby employing scanning electron microscope (SEM)fractography.

EXPERIMENTALMaterialsThe matrix material used in this work was the medium-viscosity epoxy resin diglycidyl ether of bisphenol-A (commercial trade name, LAPOX L-12) alongwith a room-temperature curing hardener (aliphaticpolyamine, K-6) supplied by Atul India Ltd. The fibresused were E-glass’ short fibres having a diameter of10 µm and a length of 6 mm, thus yielding a high aspectratio. The density of the fibres was 2.54 g cm−3. The‘as-supplied’ fibres had an epoxy compatible surfacefinish. As described above, particles of the well-knownmineral family corderite were added to the system;the particle sizes varied from 250 to 650 µm withthe largest particle sizes meeting the ‘sieve 44 BSSspecification’. Further data for the filler included thefollowing: compressive strength, 350 MPa; modulus of

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elasticity, 3.7 GPa; hardness, 7 (on the Mohs scale);crystal structure, orthorhombic; density, 2.5 g cm−3.Its chemical formula was 2MgO·2Al2O3·5SiO2.

FabricationThe composites were prepared by mixing pre-weighedamounts of resin and hardener (in a proportion suchthat the latter was 10 wt% of the former) in a beakerwith gentle stirring (so as to minimize air entrapment),following which the reinforcements were added to thesolution and the mixture was uniformly stirred toobtain a homogeneous system. The mixture was thenslowly poured into a prepared mould and allowedto cure for 24 h. The mould, made of aluminium,was coated with a layer of silicone grease, a mouldrelease agent, to facilitate easy removal of the casting.The composites produced by introducing differentamounts of reinforcement are classified as follows.

Only fibre-reinforced composites were cast first.Thus, for instance, the composite having 7 vol% offibres was abbreviated as 7F in this work. Followingthis pattern, slabs bearing the nomenclature 1F, 2F,4F, 5F and 6F were also cast. Then, keeping thetotal reinforcement content at 7 vol%, compositescontaining both fibres and particles were cast. Thecomposite having 1 vol% fibre and 6 vol% particleswas designated as 1F6P, and similarly the compositeslabs, according to the coding, 2F5P, 3F4P, 4F3Pand 5F2P (where the numerals before the letters ‘F’and ‘P’ stand for the volume percentage of fibresand particles in the resin system, respectively), werefabricated. In order to obtain a comprehensive picture,a system containing only particles (ie no fibres) wasalso cast. The latter had 7 vol% particles and this castslab, following the earlier pattern, was coded as 7P.Low-value reinforcements were specifically chosen forstudy as the ‘resin smeal’ around the reinforcementswould be better. In addition, the chances of clusteringof fillers are lesser at these levels when compared tolarger-level reinforcement-bearing systems.

TestingUnnotched impact test samples of dimensions55 mm × 10 mm, with a thickness generally of about4.25 mm, were cut from the cast slab by using adiamond-tipped cutting machine to produce a smoothsurface finish. The impact tests, on the above spec-ified geometry of test coupons, and not conformingto ASTM specification26 (owing to the slab thicknessduring casting being of a smaller size), for relativecomparison of performance as envisaged in this study,were conducted by using a Tinius Olsen, pendulumtype, Model 84 universal impact tester in a mountingresembling the Charpy type positioning of test sam-ples. Impacts were made on one face of the thicknesswith the width face resting on the flat end supportsprovided in the test set-up. The pendulum, with amass of 27 kg, when positioned at an angle of 15 ◦and released could provide a maximum energy of 8.2 Jat a maximum velocity of 0.8 m s−1. The test results

provided by the system were in the form of plots ofload and energy versus time, or load versus deflection.The load data for all fibres, as well as in the hybridsystems, were normalized with respect to 7P, whichdisplayed the lowest of the recorded strength values.In each category, a minimum of five samples weretested and the average data value thus evaluated usedfor the present analysis.

RESULTS AND DISCUSSIONThe scatter observed during the experiments, alongwith the average maximum impact loads, are recordedin Fig 1 from which it is clear that the loads sustainedby the fibre-bearing systems are much higher thanthat for the particle-bearing case (ie 7P). From this,it is clear that, under impact, for identical levelsof reinforcements (ie when 7P and 7F data arecompared), the fibrous systems perform better thanthe particle-bearing ones. The reason for this could betraced to fibres acting as barriers to crack propagationand to detour the growing crack around them. Theload borne by the system becomes enhanced if thefibres offer resistance to the dynamic loading. Such atrend being high for 7F, this sample shows the highestmaximum load and energy (Figs 1 and 2 respectively).

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Figure 1. Normalized maximum load data for ‘fibre-only’ or‘particle-only’-bearing composites.

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Figure 2. Total impact energy absorbed by ‘fibre-only’ or‘particle-only’-bearing composites.

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To substantiate these deductions, the failed sampleswere examined by using SEM and the details presentedin the following.

The 7F sample (Fig 3) shows how a group offibres resist the crack path. The crack along ‘ABC’terminates well before reaching the fibres. Somefibres have fragmented while the others remain intact,thus contributing to the enhanced energy (Fig 2)and maximum load (Fig 1) in this system. Furtherexamination of the matrix by SEM showed thepresence of undulations (Fig 4) due to the irregularflow of fracture in these materials, hence supportingthe view that the crack paths were made to detourdue to the resistance offered by the fibres, whichare incidentally seen at the top and right corner of thismicrograph (Fig 4). Together, these situations favour alarge absorption of energy in this system (Fig 2). Thus,the significant role of fibres in enhancing the loadsustained and energy absorbed by the sample during

C BA

Figure 3. Fracture features in the highest-fibre-bearing epoxy resincomposite (7F), showing a crack ‘ABC’ in the matrix regionterminating before approaching the fibre-rich area, plus the presenceof fragmented fibres.

Figure 4. The matrix region showing undulations and an uneventerrain in the failed 7F composite.

dynamic instrumented impact is brought to evidenceby this experiment on the highest fibre-bearing systeminvestigated in our work. How important is the fibrecontent in the composite system needs to be examined,especially in light of the presence together of two typesof reinforcements, namely, the higher-aspect-ratio-bearing regular-shaped fibres and the lower-aspect-ratio-bearing oxides with irregular surfaces, in thematrix system. To understand these aspects, in thefollowing the early part will dwell on the fibre issue,while the latter part takes up the case where both ofthe differing aspect-ratio-bearing materials are presentin the system as hybrid reinforcements.

Coming to the ‘fibre-only’ case, visual macroscopicexamination of the highest fibre (ie 7F)-bearingcomposites, as briefly stated earlier, showed featureswhere the fractures were totally uneven. What featuresprevail in the 7P system needs to be looked into andthen compared with the 7F case. Therefore, medium-range-magnification electron micrographs of thesesamples are presented in Figs 5 and 6, corresponding,respectively, to the 7F and 7P composition. Theformer, as stressed before, clearly shows undulationsand a rough terrain, while 7P displays flat featureswith marks resembling those of a river. Such featuresin 7P are typical of fast fracture and hence lowenergy absorption in this sample (Fig 2). Hence, SEMfully lends support to the mechanical test data. Thevast difference in load (Fig 1) and energies (Fig 2)absorbed by 7F and 7P thus becomes obvious fromthese comparative microscopic presentations of thefracture features.

Having seen the importance of fibres over par-ticles in this brief way, it is essential to establishthat the fibre content has a bearing first on theload borne by the system and then on the energyabsorbed by the material. This can be done byincluding into an epoxy a gradation of increas-ing fibre levels and then recording the values ofload and energy. When this exercise is carried

Figure 5. A predominantly matrix-rich region showing unevenfracture features in the ‘fibre-only’ (7F) composite.

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Figure 6. A ‘particle-only’ reinforced (7P) system showing flatterfeatures in the matrix, along with ‘river-like’ marks.

out for these ‘fibre-only’ reinforcement-bearing sys-tems, they showed a generally rising trend withfibre content, with the only exception being 6F(Figs 1 and 2).

To record the features in the low ‘fibre only’-bearingsystems, a 2F sample was examined under themicroscope. It is interesting to note that this showscleavage steps in the top and bottom half of themicrograph, while the central mid-zone from left toright shows uneven features (Fig 7). In this way, the 2Fsample displays some features typical of that recordedfor 7P (Fig 6), as well as those of 7F (Fig 5), therebygiving the indication that its characteristics are midwaybetween the ‘all-particle’-reinforced 7P system on onehand and the ‘all-fibre’-reinforced 7F system on theother. The histogram data presented in Figs 1 and 2support this deduction where the values for 2F arehigher than those for 7P but much lower than thosefor 7F. In this way, the utility of microscopy has againbeen stressed.

Figure 7. The 2F composite sample, showing cleavage steps in thematrix at the top and bottom half of the micrograph, while the centralregion from left to right displays uneven features.

Whether such a microscopic approach can solvethe low energy recorded in the 6F case is a pointfor consideration now. Figure 8, for this higher-fibre-bearing system, shows what appears to be a darkband in the top and right-hand side portions of themicrograph. A careful examination of this darkerstructure reveals it to be a cavity, at the left centreof which a single fibre protruding from the matrixbeneath can faintly be seen. It is well recordedin the literature that defects such as these cavitiesor voids trigger premature failure in the system byacting as ‘stress raisers’ during testing. This role ofthe voids in reducing the load and energy becomesaccentuated when dynamic testing is carried out,in which situations these regions act as zones forcrack initiation and growth. Hence, SEM serves as agood and useful tool in resolving such discrepanciesobserved during mechanical testing.

Having established that fibres are more importantas reinforcement when compared to particulates,how the dispersal of particles and short fibres inepoxies affects the strength of the composites willnow be considered.

The hybrids show again a trend where thenon-hybrid and the highest-fibre-bearing compositesystem, ie 7F, have the highest load and energy (Figs 9and 10). The systems where the particles and fibres arepresent together display a small and steady increasein load and energy with increased content of fibres.This clearly shows that, of the two reinforcements,it is the fibres which contribute to the higher-load-bearing ability. This conclusion is strengthened when7P is compared with 1F6P, with the latter showinga substantial increase, both in terms of load-bearingand energy-absorption capabilities (Figs 9 and 10).To find out how, when identical volume fractionsof the reinforcements are put together, such systemsperform when an interchange in the levels of particlesand fibres are effected in the composites, two sets ofdata points were taken. In one case, 2F5P is compared

Figure 8. The 6F composite sample, where a larger darker cavity-likeregion appears sandwiched between the fibre-bearing areas.

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Figure 9. Normalized maximum load data for the hybridcomposite systems.

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Figure 10. Total energy variation in the hybrid composite systems.

with 5F2P, while in the other, 3F4P is compared with4F3P. In all of these cases, as outlined above, thetotal volume fraction of the reinforcements is keptat 7 vol%. Now taking the first set, 5F2P shows amuch higher load and energy when compared to 2F5P(Figs 9 and 10), thus supporting the earlier deductionthat it is the fibres which dominate the response toimpact in these hybrid-reinforced composite systems.The difference between the levels of energy absorbedin the higher- and lower-fibre composites is substantialin this case. When this exercise was performed on thesecond set (ie 3F4P versus 4F3P), the latter againshows higher levels of load and energy, thus reinforcingthe main deduction of this work that fibres dominatethe impact response. However, the numerical values ofthe differences in the levels for both energy absorptionand load are lower in this set when compared to theearlier mentioned 2F5P and 5F2P set (Figs 9 and10). These lower differences in one case and higherdifferences in the other are because of the fact that,in one set (ie 3F4P versus 4F3P) the volume of fibresrises by 1 % while in the other (ie 2F5P versus 5F2P)it becomes enhanced by 3 %. This again supports therole of fibres in this study. The improved mechanicalproperties observed when carbon fibres and Al2O3

Figure 11. A hybrid sample showing a matrix-rich region where a‘tear-out’ of the resin can be seen at a few places of the rough terrain.Imprints of separated fibres can also be observed on the right centreof the micrograph of this 5F2P sample.

Figure 12. A lower-fibre-bearing hybrid composite (ie 2F5P) showingdistinct cleavage in the matrix-rich region.

fillers are used in epoxy matrices support these presentresults.22

To gather information on the microscopic scale,the representative features seen in the first set arepresented in Figs 11 and 12 for the 5F2P and 2F5Pcases, respectively. Figure 11 displays a very roughterrain where the matrix appears to be ‘pulled out’from its original position due to tearing. The fibre thatstayed alongside has left a clear imprint of its presencebefore the split of the test coupon. This imprint canbe seen in the form of a depression in the right centreof the micrograph. The lower-fibre-bearing system, atsuch higher magnification, displays no such features(Fig 12). Instead, it illustrates a fast fracture cleavagepattern on its surface (Fig 12). The matrix being tornapart, distinctly seen in Fig 11, is conspicuous by itsabsence in Fig 12. Such a feature can be invoked toexplain the difference which results in this hybrid, ie

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5F2P, namely, the display of higher load and energywhen compared to the 2F5P case.

When such an exercise is carried out for the secondset ie 3F4P versus 4F3P, the following features areobserved. The high-magnification micrographs for thisset are presented in Fig 13 for the higher-fibre, ie4F3P, and in Fig 14 for the lower-fibre, ie 3F4P,cases. Both of these figures show ‘pull-outs’ of thefibres from the matrix. A higher resistance is offeredby the matrix in the 4F3P case, while the consequenttear of the matrix is seen in the region marked ‘A’ inFig 13. It is this additional feature which makes 4F3Pdisplay a larger strength and energy than that recordedfor the 3F4P case.

Now, considering another aspect, Fig 15 shows ageneral rise in the initiation and propagation energiesfor the non-hybrids with increasing fibre content,with exception of the 6F system. Of the two, iethe initiation and propagation energies, the rise is

A

Figure 13. The tear-out at ‘A’ and the fibre ‘pull-out’ seen in ahigher-fibre-bearing hybrid composite (ie 4F3P). The left half showsthe cavity left by the ‘pulled-out’ fibre.

Figure 14. The situation prevailing in a lower-fibre-bearing hybridcomposite (ie 3F4P), showing a protruding fibre, in addition to which a‘pulled-out’ fibre, along with its remaining imprint, can alsobe observed.

much steeper in the propagation part as the fibrecontent in the system increases. This again supportsthe view that the fibres have a distinct role toplay in the level of absorption as the reinforcementcontent increases.

Coming to the hybrids, the propagation energy againshows a much steeper rise than the initiation energyas the fibre content increases (Fig 16), thus clearlyreinforcing the deduction arrived at while interpretingthe earlier data obtained for non-hybrids. When anexercise in comparing two sets of hybrids, carried outfor the load and energy cases earlier, was performed,it is seen that 5F2P shows much higher initiationand propagation energies when compared to 2F5P(Fig 16). Of the two energies, it is the propagation thatis much larger in 5F2P, which can be interpreted tomean that for identical volume levels of reinforcement,the large difference in the fibre content for 5F2P and2F5P is responsible for the higher propagation energyin the former. This statement is reinforced when the4F3P data are compared with those of 3F4P. Theformer shows both higher initiation and propagationenergies when compared to the lower-fibre-bearinglatter case.

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Figure 15. Initiation and propagation energy data for the ‘fibre-only’or ‘particle-only’-bearing composites.

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Figure 16. Initiation and propagation energy data for hybridcomposite systems.

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Figure 17. Comparison of propagation energy data for plain andhybrid composite systems.

Extending this work to another view point, thepicture that emerges as for as propagation is concernedwhen oxide particles are introduced into the system,is presented in Fig 17. To make the comparisoncomplete, at the two extremes of this figure, thedata obtained for 7P and 7F, presented in Fig 16,are included. The additional data incorporated inthis figure represent information obtained for eachlevel of the system when only fibres are present asreinforcements. How, consequent upon introductionof particles, a change, if any, in the propagationphase is examined here. This shows that in allhybrid cases, the propagation energies are higherwhen compared to the ‘fibre-only’-bearing systems.This increase is felt more intensely at the higher-fibre-volume (ie lower-particle-content level) than atthe lower-fibre-content level. Thus, 1F6P shows amarginal increase when compared to 1F, while 5F2Pshows a noticeable increase when compared withthe ‘fibre-only’-bearing system ie 5F (Fig 17). Thesedata demonstrate that from an engineering propertypoint of view it is attractive to work with larger-fibre-bearing systems where a low introduction ofdispersed, low-aspect-ratio-bearing irregular shapedparticles is accomplished. Summing up this work, thissubstantiates the general view that a judicious selectionof hybrid systems can improve the dynamic responsesof short-fibre-reinforced epoxy systems.

CONCLUSIONSAs generally stated, the increased presence of fibresleads to an enhancement of maximum load andenergy absorbed by these composite systems. Thehybrids show an enhancement in these properties of

a marginal nature in the maximum load while withregard to energy, a substantial improvement is seenwith increased fibre content in the system. Fromthe total energy data, when the component relatingto propagation energy is separated, this seems to beinfluenced more by the presence of smaller amounts ofparticle reinforcement. Since studies with the hybridsyielded larger values for the energy and loads whenthe fibre content in the total system was higher thanthe filler content, this leads to the obvious fact that,of the two reinforcements, it is the fibrous type whichdecides the impact data by dominating and dictatingthe failure features. The fracture features bring outthe failure features, which are flatter for all particle-bearing composites, while a jagged and rough terrainis observed for the ‘all-fibre’-bearing systems.

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