Mechanical Characterization of Hybrid Thermoplastic Composites of Short Carbon Fibers and PA66/PP

Transcription

1 Aville online t Mechnicl Chrcteriztion of Hyrid Thermoplstic Composites of Short Cron Fiers nd PA66/PP B. V. Lingesh 1, B. N. Rvikumr 1, B. M. Rudresh 2 * Indin Journl of Advnces in Chemicl Science 1 Deprtment of Mechnicl Engineering, Bnglore Institute of Technology, Bengluru, Krntk, Indi. 2 Deprtment of Mechnicl Engineering, Government Engineering College, Krishnrjpete, Krntk, Indi. Received 22 th Septemer 2016; Revised 30 th Septemer 2016; Accepted 05 th Octoer 2016 ABSTRACT The hyrid effect of fiers on the mechnicl ehvior of thermoplstic composites is the most importnt for structurl pplictions. This rticle dels with the individul nd hyrid effect of 10 wt. % short glss fiers nd 10 wt. % short cron fiers on the mechnicl ehvior of 80/20 wt. % PA66/PP lend. These composites re produced y melt mixing method using twin screw extruder followed y the injection molding. The mechnicl properties such s tensile, flexure, nd impct ehvior of the composites re studied s per ASTM method. Further, the hrdness nd density of the composites were lso discussed. Experimentl results reveled tht the reinforcement of hyrid short fiers into the lend gretly enhnced mechnicl ehvior of PA66/PP composites. Increse in tensile strength y 77%, 104% flexurl strength, nd 20.8% reduction in elongtion ws exhiited y the lend due to the hyrid effect of fiers. Significnt improvement in strength of the composites ws oserved due to individul effect of the fiers. The synergistic effect etween the fiers nd mtrix lend supported in improving the mechnicl ehvior. The strin rte of the hyrid composites ws deteriorted due to the hyrid effect. The impct strength of the hyrid composites is reduced due to the rittle nture of the hyrid filled composites. Fier frcture, fier pull-out, nd fier mislignment re the some of the mechnisms oserved through scnning electron microscopy photogrphs. Keywords: PA66/PP, Hyrid mterils, Cron fiers,mechnicl, Blends. 1. INTRODUCTION Polymer composites re the clss of composite mterils for structurl pplictions. Polymer composites re often used s the sustitute for the metl sed ones in the mechnicl industries. They re used in the penl of solr ords, utomoile ccessories, polymer gers, ody of modern crs, rtchets of dminton, etc. However, the mechnicl performnce of the polymer is only the prmeter which cn hold the strength of them in the field of industries. Homopolymer could not stisfy the demnd rising from the situtions where the comined effects of mechnicl nd triologicl properties re required. Therefore, it is required to improve the properties of the homopolymer to suit the ove mentioned situtions. Copolymeriztion, polymer lending nd reinforcing the polymers y fiers nd fillers re importnt methods for the polymer modifictions. Polymer lending is fscinting in polymer modifiction ecuse it hs very simple processing nd unfolds unlimited possiilities of producing mterils with vrile properties [1]. Polymer lends *Corresponding Author: E-mil: mrudreshn@gmil.com Phone: re mixtures of two mcromoleculr species, polymer nd/copolymers. Mixing two polymers usully leds to immiscile lends chrcterized y corse, metstle morphology, nd poor dhesion etween the phses. Elongtion t rek, toughness, nd tensile strength re the mechnicl properties gretly ltered y the phse seprted morphology [2]. Therefore, selection of the lend ssocites determines the effective polymer mteril. Mny reserchers hve reveled tht the ddition of fillers nd fiers to the polymer mtrix hs gretly enhnced the mechnicl ehvior of the composites. A lot of reserch hs een mde to improve the mechnicl properties using reinforcing the fiers with vrious net polymers. The strength nd stiffness of the polymer mtrix cn e effectively improved y reinforcing fiers. Glss nd cron fiers re most widely used reinforcing gents in thermoplstic mtrix ecuse of good lncing properties. These fiers re usully sized to permit good onding with the mtrix, producing mteril of high flexurl, nd tensile strength. The ddition of reinforcing gents such s glss nd cron prticulrly 425

2 in the form of fiers enhnces the mechnicl properties of polymer composites. Mnoj Kumr et l. [3] studied the effect of nn nturl fiers on the mechnicl ehvior of high density polyethylene nd polymide 66 (HDPE/PA66) lend composites. They stted tht the tensile strength of the treted nn fier composites is etter thn the non-treted ones. A similr trend ws noticed for the flexurl ehvior nd tensile modulus up to 40 wt. % of nn fiers with lowering the vlue of impct toughness. They reveled tht the effect of sizing gent is most pprecile in improving the mechnicl ehvior of nn fier filled composites. Bhdur nd Cheng [4] studied the reinforcement effect of short glss fiers (SGFs) on the mechnicl ehvior of polyester composites. The tensile strength, flexurl strength, nd hrdness of the polyester were incresed due to the effect of SGF loding. They lso reveled tht the effect of comptiilizer on the mechnicl ehvior of the polymer composites. The effect of long glss fiers on the mechnicl ehvior of polypropylene (PP) composites ws studied y Hrtikinen et l. [5]. They oserved tht the ddition of fier into the PP improved the tensile strength, frcture toughness, nd lso tensile modulus of the composites. Pliyik nd Bhdur [2] studied the hyrid effect of polytetrfluoroethylene (PTFE) nd copper oxide on the mechnicl ehvior of SGF filled PA6 nd HDPE lends. There is 60% increse in tensile strength for 15% of SGF in the lend. Further the hrdness of the lend ws incresed in the similr wy. However, the ddition of PTFE into SGF filled lend PA6/HDPE decresed the tensile strength of the composites. Run et l. [6] studied the reinforcement effect of short cron fiers (SCF) on the mechnicl ehvior of poly trimethylene terephthlte (PTT/SCF) composites. They reveled tht the tensile strength nd the rupture strength re incresed with incresing content of SCF. The mximum vlue of the impct strength ws otined for 5 wt. % of SCF in the mtrix. Run et l. [7] studied the mechnicl properties of SCF reinforced PTT/Acrylonitrile-Butdiene-Styrene (ABS) lend. When the ABS content ws 5 wt. % in the lend, SCF hd significntly improved the flexure, tensile nd impct strength of the lends. The SCF hs good interfce dherence with the mtrix. The storge modulus increses s the content of SCF increses in the lend. Fu et l. [8] studied the tensile properties of SGF nd SCF reinforced PP composites. The results out the composite strength nd modulus were interpreted using the modified rule of mixture equtions y introducing two fier efficiency fctors respectively, for the composite strength nd modulus. It ws found tht for oth types of composites the fier efficiency fctors decresed with incresing fier volume frction nd the more rittle fier nmely cron fier corresponded to the lower fier efficiency fctors thn glss fier. Yun et l. [9] studied the effect of coupling gent on mechnicl properties of glss fier reinforced SCF filled HDPE composites. They showed tht incresing coupling gent will improve the onding strength etween glss fiers nd the mtrix. They proved tht the coupling gent will ct positively in improving the mechnicl ehvior of SGF reinforced SCF/HDPE composites. The mechnicl ehvior of cron fier reinforced PA composites is studied y Botelho et l. [10]. Two types of composite mtrices ws studied PA6 nd PA66 oth reinforced y cron frics nd unidirectionl cron fiers. A slight increse of mechnicl ehvior of PA6/SCF nd PA66/SCF ws oserved. Shu et l. [11] reported the development nd chrcteriztion of prticulte filled glss fier reinforced hyrid composites. They studied the effect of lumin filler on the 40 wt. % of SGF filled polyester composites. The mechnicl ehvior of SGF filled composite decreses s the percentge of lumin in the composites increses. Pliyik nd Bhdur [12] studied the mechnicl ehvior of PA6/HDPE lends reinforced with SGF. They showed tht the ddition of 5-15 wt. % of SGF into 80 wt. % PA66-20% wt. % HDPE improved the tensile strength of the lend from 20% to 60%, respectively. Yuqin nd Junlong [13] reported the mechnicl properties of cron fier reinforced polyoxymethylene (POM) composites. They reported tht the ddition of SCF improves the tensile strength of POM. Chen et l. [14,15] studied the effect of short glss/cron fiers on the mechnicl properties of PA66/polyphenylenesulphide (PPS) lend. They showed tht the ddition of wt. % of SGF gretly improved the mechnicl properties of PA66/PPS Blend. On the other hnd, 30 vol. % of SCF hd the est mechnicl properties of PA66/PPS even though it hs negtive effect on the sme. Experimentl investigtion on the effect of glss fiers on the mechnicl properties of PP nd PA6 plstics were reported y Gullu et l. [16]. They showed tht SGF filled PA6 nd PP hd exhiited etter mechnicl properties. Investigtion on the mechnicl properties of PPS/SCF composites nd PA6 filled PPS/SCF composites were studied y Jin nd To [17]. They showed tht etter flexurl strength ws otined for 25 wt. % of SCF in PPS. Furthermore, they proved tht the ddition of 6 wt. % of SCF into PA66/SCF exhiited etter flexurl strength thn PPS/SCF composites. Co et l. [18] reported the effect of slt fier in ultr-high moleculr weight polyethylene. Increse in slt content in the composite led to decrese in toughness nd increse in strength, hrdness, nd creep resistnce. Zhou et l. [19] studied the effect of cron fier reinforcement on the mechnicl properties of PA6/PPS composites. Addition of 15% of SCF into the lend PA6/PPS hd gretly improved the mechnicl ehvior of the composites. There ws 45% increse in tensile modulus of filled composites ginst the lend. Similrly, the ending stress nd ending modulus re lso followed the sme wy. The impct strength of 426

3 the lend PA66/PPS decresed with the ddition of SCF with increse in hrdness of the lend. Wu et l. [20] studied the mechnicl properties of glss fier nd cron fier reinforced PA6 nd PA6/cly nnocomposites. The results showed tht the mechnicl properties of polymode 6/cly nnocomposites re superior to those of SCF or SGF filled PA6 composites in terms of tensile, flexurl nd modulus without scrificing the impct strength of the composites. The effect of nnoscle cly on toughness is more significnt thn tht of the fier. Mouhmid et l. [21] experimentlly investigted the mechnicl ehvior of glss fier reinforced PA66. They studied y reinforcing 15, 30 nd 50 wt. % SGF into PA66. They concluded tht the glss fier reinforced PA66 exhiits improvements in its mechnicl strengths. Experimentl results showed tht the studied composite is strin rte, temperture nd fier volume frction dependent mteril. Rudresh nd Rvi Kumr [22] studied the effect of SGF loding on the mechnicl ehvior of PA66/PTFE lend. They showed tht the ddition of SGF gretly enhnced the mechnicl ehvior. They studied for 5, 10, 15, 20, 25, nd 30 wt. % of SGF effect on 80/20 wt. % PA66/ PTFE lend. The improved mechnicl ehvior continued up to 30 wt. % of SGF in the lend. Oviously, elongtion to rek decresed due to the rittle nture of PA66/PTFE/SGF composites. PA66 is high performnce thermoplstic polymer. PP is one of the crystlline high performnce thermoplstic polymers. Very less dt re reported on the PA66/PP lend. The lend of PA66/PP will e the est lend for the polymer mtrix. In spite of the fct tht polymer composites re used in such structurl pplictions, no dt re reported on the influence of PP in PA s lend with hyrid fiers such s SGF nd SCF. To design the structurl pplictions with hyrid fiers, keeping this in view, the hyrid effect of SCF nd SGF on the tensile, flexurl nd impct ehvior of PA66/PP lend is discussed. Furthermore, the hyrid effect on the specific properties which chrcterizes the mechnicl ehvior of the developed composites ws. 2. MATERIALS AND PROCESSING 2.1. Mterils The mterils used in the present investigtion PA66, PP, silne coted SGF nd SCF re listed in Tle 1. The detils of mterils nd their specifictions re lso tulted in the sme Tle Friction of Blend nd their Composites The polymers PA66 nd PP with proper proportions (Tle 2) were dried t 80 C for 48 h efore mixing to void plsticiztion, hydrolyzing effects from humidity nd to otin the sufficient homogeneity. The plsticiztion is phenomenon of chnge in therml nd mechnicl properties of given polymer which involves (1) lowering of rigidity t room temperture, (2) lowering of temperture t which sustntil deformtion cn e effected with no too lrge forces, (3) increse of elongtion to rek t room temperture, nd (4) increse of toughness down to the lowest temperture of serviceility. PA66 nd such polymers re very susceptile to moisture, which my deteriorte the mechnicl strength of the composites. For this purpose, plsticiztion nd hydrolyzing effects must e voided efore sujecting ll the ssocites of the composites to compounding process nd friction. The composition of the lend, sline coted sized SGF, nd SCF re mixed in proper proportions. The mixed mterils were extruded using Brender co-rotting twin-screw extruder (Mke: CMEI, Model: 16 CME, SPL, chmer size 70 cm 3 ) (Figure 1). The extruder consists of five heting zones nd the temperture mintined in these zones were zone 1 (220 C), zone 2 (235 C), zone 3 (240 C), zone 4 (265 C), nd zone 5 (270 C), respectively, nd the temperture t the die ws set t 220 C. The extruder screw speed ws set t 100 rpm to yield feed rte of 5 kg/hr. The extrudte otined ws in the form of cylindricl rod which ws quenched in cold wter nd then plletized using Plletizing mchine. During initil stge, round 1 to 1.5 kg of initil extrudte ws Figure 1: Brender Co- rotting twin screw extruder. Tle 1: Dt nd detils of the mterils used. Mterils Designtion Form Size (µm) Trde nme Mnufcturer Density (g/cc) Polymide PA66 Grnules Zytel 101L NC010 Dupontco. Ltd Polypropylene PP Grnules MP1000 Dupontco. Ltd 0.95 Short glss fier SGF Cylindricl Length=2 3 mm Fine orgnics, Mumi 2.5 Short cron fiers SCF Cylindricl Length=2 3 mm Fine orgnics, Mumi

4 removed to get the pure composites nd to remove impurities from the previous stroke of the extrusion. Before injection molding, ll polymer lended composite pllets were dried t 100 C in vcuum oven for 24 h. All specimens were injection molded from the pelletized polylend mteril otined from corotting twin screw extruder. The temperture mintined in the two zones of the injection molding rrel were zone 1 (265 C) nd zone 2 (290 C), nd mold temperture ws mintined t 65 C (Figure 2). The screw speed ws set t rpm followed y r injection pressure. The injection time, cooling time, nd ejection time mintined during injection molding were 10, 35, nd 2 s, respectively. All the molded specimens s per ASTM D638 (tensile Figure 2: Injection moulding mchine (GLS Polymers, Bnglore, Indi). Tle 2: Formultions of composites in weight percentge. Mteril ID Composition PA66 PP SGF SCF 1T Blend (PA66/PP) G Blend (PA66/PP)/SGF C Blend (PA66/PP)/SCF CG Blend (PA66/PP)/SGF/SCF PA66: Polymide 66, PP: Polypropylene, SGF: Short glss fier, SCF: Short cron fiers test), ASTM D790 (flexure test), nd ASTM D256 (impct test) were inspected nd tested visully nd those found defect were discrded for testing. 3. MEASUREMENT OF MECHANICAL PROPERTIES The mechnicl properties such s tensile, flexurl, impct strength long with density, nd hrdness of the composites re mesured s per ASTM. The tensile strength nd the tensile elongtion t rek re mesured using Universl testing mchine (JJ Lloyd, London, United Kingdom, cpcity 1-20KN) in ccordnce with ASTM D638 t constnt strin rte of 5 mm/min. ASTM D 638 Type 1 stndrd dimensions re used (Figure 3). Flexurl strength or three point ending were crried out on the sme mchine y chnging the jws of the set up nd the specimen cts s simply supported em sujected to point lod t the middle. The flexurl strength nd flexurl modulus were determined t the rte of 1.33 mm/min s per ASTM D790. The stndrd specimen dimensions for the flexurl strength is 125 mm 12.7 mm 3.2 mm (Figure 3). The Notched Izod impct strength ws determined using ASTM D256 using Izod impct testing mchine t the striking rte of 3.2 mm/s (Figure 3c). The ASTM stndrds for the mechnicl testing re shown in Figure 3. All these tests were conducted t the room temperture. Minimum of three smples were tested for the dt representtion. On the other hnd, the density nd the hrdness (Shore D) of the composites were determined s per ASTM D792 nd ASTM D2240, respectively. 4. RESULTS AND DISCUSSIONS 4.1. Effect of SGF, SCF, nd their Hyrid on the Density nd Tensile Behvior The effect of fiers on the density of PA66/PP lend is shown in Figure 4. The ddition of 10 wt. % SGF into the lend incresed the density of PA66/PP lend. This is purely ttriuted to the dense nture of silne coted glss fiers. Further, ddition of 10 wt. % SCF into the lend incresed the density of the lend ut less thn tht of SGF. This decrese in density is due to the less dense SCF. But inclusion of oth the fiers into the lend gretly enhnced the density of lend. Tle 3: Tensile properties of PA66/PP composites. Properties Units ASTM 1T 1G 1C 2CG Density gr/cc ASTM D Tensile strength MP D % Elongtion % Pek lod N Stiffness N mm Specific stiffness N mm 2 /Kg 0.91E E E E+08 Specific strength N mm/kg 3.68E E E+07 6E+07 PA66: Polymide 66, PP: Polypropylene 428

5 c Figure 3: Specimen stndrds :() ASTM D 638 () ASTM D790 nd (c) ASTM D256 Figure 4: Individul nd hyrid effect of fiers on the properties of polymide 66/polypropylene lend: () Density nd () Tensile strength nd % Elongtion. Almost 8% increse in density y the hyrid effect of fiers thn tht of net lend. Addition of SGF into PA66/PTFE lend incresed the density of the lend [22]. The individul nd hyrid effect of fiers on the tensile strength nd percentge elongtion re shown in Figure 4. The improvement in the tensile strength ws seemed to e the function of fier reinforcement. The tensile strength of PA66/PP lend is N/mm 2 (Tle 3). However, the effect of 10 wt. % SGF improved the strength of the lend to 64.6 N/mm 2 which is 62.39% increse. This enhncement of strength is gretly ttriuted to the silne coted SGF. The silne will ct s coupling gent in developing the interfcil ond etween the mtrix lend nd the SGF. The slenderness rtio (l/d) of the SGF lso promotes the strength y incresing the surfce re of contct with the mtrix. The interfcil ond etween the SGF nd the mtrix lend hs gretly comptiilized for the effective development of strength of the filled composite. The good elstic modulus of SGF supported the lend mtrix in resisting the externl lod. Further, ddition of SCF into the lend improved the strength y 56% thn tht of net lend. SCF re good in specific modulus nd specific strength. This mde the composites to possess high strength. The interfcil ond developed etween the lend nd SCF is superior. SCF s re rigid nd very tough. The results reveled tht the incorportion of SCF improves oth rigidity nd the toughness of the polymer lend. The degree of comptiility etween SCF nd lend were good for the effective development of the mterils. The hyrid effect of fiers on the tensile strength of composite is most pprecile. It is 70.3 N/mm 2 which is lmost 77% increse over the net lend. This shows tht the effective interfcil ond nd the network etween thermoplstics nd the fiers were estlished during the process of polymer lending. The lod crrying cpcity of the fiers through mtrix is very good. Further, the synergistic effect of fiers hs contriuted lot to the development of strength in the composites. Furthermore, SCF s nucleting gent cn increse the crystlliztion rte nd decreses the crystl size of the lend [6,7]. Due to the hyrid effect of fiers, sustntil improvement in tensile strength ws exhiited y PA66/PP lend. Among the studied composites, hyrid composite is most pprecile. The hyrid effect of fiers on the percentge elongtion of PA66/PP composites is shown in Figure 4. The decrese in percentge elongtion fter the hyrid fier reinforcement into the lend PA66/PP ws noticed. The mximum reduction in elongtion ws noticed for SCF filled PA66/PP composites. This is minly ttriuted to the synergistic effect etween the ssocites of the thermoplstic lend nd the cron fiers. The SCF re rigid nd toughened in nture. The PA66/PP lend ws siclly crystlline in nture. However, the ddition of 10 wt. % SGF mde the mteril little ductile therey incresing the ductility of the composite mteril. Furthermore, the ddition of 10 wt. % SCF reduced the elongtion of the filled composite. This my e due to the crystlline nd rittle nture of SCF. But the reduction in percentge elongtion of the lend ws exhiited due to the hyrid effect of fiers. Among the studied composites, hyrid composites hd the lest elongtion. The lod versus deflection curve, the stress-strin curve, specific stiffness, nd pek lod for the hyrid fier filled PA66/PP lend re shown in Figure 5-d. Both lod-deflection nd stress-strin curve followed the liner trend up to the ultimte point. From Figure 5d, the pek lod for the lend is 1617 N. However, the reinforcement effect of fiers shifted the pek lod to higher point which is 56, 62 nd 77% higher thn tht of net lend for SCF, SGF nd hyrid fier filled PA66/PP composites, respectively. The stress-strin ehvior of hyrid fier filled PA66/PP composites is shown in Figure 5. The hyrid effect of fiers on the stress-strin ehvior mintined the liner trend up to the pek point. SGF filled PA66/PP lend initilly experienced less stress up to the strin rte of But sudden increse in stress ws noticed during the finl elongtion of the composites. This is purely ttriuted to the rittle nture of the composites. The ehvior of the lend is uniform throughout the test. This shows the ductile nture of the composites. Among the studied composites, hyrid composites hd the lest strin rte. The individul nd hyrid effect of 429

6 improve the strength of the hyrid composites PA66/ PP/SGF/SCF. c d Figure 5: Individul nd hyrid effect of fiers on the properties of polymide 66/polypropylene lend: () Lod versus deflection, () Stress strin curve, (c) Specific stiffness nd specific strength, nd (d) pek lod. Figure 6: Individul nd hyrid effect of fiers on the properties of polymide 66/polypropylene lend: () Flexurl strength nd % deflection nd () Flexurl modulus. fiers on the specific strength nd specific stiffness of PA66/PP lend composites is shown in Figure 5c. The mechnicl chrcteriztion of ny composite mteril is mesured y its specific stiffness nd specific strength. The specific strength is the mesure of rtio etween the ultimte tensile strength nd the density of the composite mterils. For the composite mterils, this rtio should e high. The specific stiffness of the composites followed the liner trend. This is due to the increse in the tensile lod of the composites. Among the studied composites, hyrid effect of fiers improved the stiffness of the hyrid composites. Similr oservtions re mde with the specific strength. The specific strength of the hyrid composite is high. This is due to the high strength of the hyrid fiers. Among the strength nlysis of the composites, it is cler tht the comptiility of the hyrid fiers with tht of the thermoplstic composites re superior when compred with the individul effect of the fiers. The higher specific stiffness of the composites is due to SGF wheres, the higher specific strength is due to SCF. The high stiffness nd high specific strength fiers developed the interfcil onding etween the mtrix lend nd the fiers to 4.2. Individul nd Hyrid effect SGF/SCF on the Flexurl Behvior of PA66/PP Blend The individul nd hyrid effect of SGF nd SCF on the flexurl strength nd % deflection due to ending of PA66/PP lend is shown in Figure 6. The flexurl strength of PA66/PP lend is 55 MP. SGF (10 wt. %) reinforcement into PA66/PP lend promoted the flexurl strength y 87%. Sme oservtion ws exhiited y the 10 wt. % filled SCF. The improved flexurl strength of the lend is ttriuted to the good lncing flexurl ehvior of the short glss nd cron fiers. The lod crrying cpcity of the composite is very good. This hs proved y the effective trnsformtion of the lod through the fiers into the mtrix. This shows tht the fier filure is only y fier pullout nd not y fier frcture. During the flexurl test, outer fiers re in tension nd inner fiers re in compression. The outer fiers my pull out from the mtrix mteril resulting in no loss of strength. However, the fiers trnsformed the lod to the mtrix which is surmounting them therey effectively receiving the lod. Fier rupture nd fier pull-out re the mjor filures noticed during the performnce. The hyrid effect of SGF nd SCF improves the ending strength of the composites y 104%. This shows tht the fiers hve very good interfcil ond with the thermoplstics. Among the studied composites, hyrid fier filled PA66/PP lend hd the etter flexurl strength. Thus, the effect of fier properties is of gret importnce for the structurl pplictions. The effect of fier reinforcement on the percentge deflection of PA66/PP lend is shown in Figure 6. Reduction in percentge deflection due to ending ws oserved during reinforcement of fiers into the lend. Reinforcing SCF into the lend hd reduced the percentge deflection y 51% ginst the lend. Blend hd the good percentge of deflection due to the ductile effect of lend. However, the ddition of fiers into the lend mde the mteril rittle nd reduced the deflection of the lend. SCF hd the gret effect in reducing the deflection of the lend. This is due to the good comptiility etween fiers nd mtrix. The dhesive ond developed etween the fiers nd the lend is very good. The hyrid effect of fiers on the deflection of the lend is very severe. Very less deflection due to ending ws otined y the hyrid fier filled lend. This shows tht the hyrid fier effect mde the mteril strong to support the ending lod. The coupling gent of SGF (Silne) nd SCF hs sized uniformly during lending to contriute eqully with tht of mtrix lend. The effect of fiers on the flexurl modulus of the studied polymer lend is shown in the Figure 6. The significnt improvement over the flexurl modulus ws noticed y reinforcing the fiers into the lend. The flexurl modulus ws incresed y 3 times tht of 430

7 net lend y reinforcing SCF. This is purely due to the good modulus nd strength of SCF. A slight decrese in flexurl modulus ws oserved y the effect of SGF on the SCF filled PA66/PP lend. Inclusion of SGF into the SCF filled polylend incresed the rittleness of the composite. The hyrid fier filled composites mke the lend to develop voids which cn initite the crck in the polylend. The lod v/s deflection nd the S-S curve for the flexurl ehvior of hyrid composites re shown in Figure 7 nd. The ending lod crrying cpcity of the polylend is less when compred to the studied Figure 7: Individul nd hyrid effect of fiers on polymide 66/polypropylene lend: () Lod versus deflection curve nd () ending stress nd strin curve. Figure 8: Individul nd hyrid effect of fiers on the impct strength nd hrdness of polymide 66/ polypropylene lend. composites. This is due to the sence of the fier. However, the inclusion of fiers mde the polymer lend stiffened nd strengthened to crry the mximum lod (Figure 7). Among the studied composites, hyrid composites hve the significnt lod crrying cpcity. The ending stress nd strin ehvior of the composites re shown in Figure 7. All the composite mterils studied hve followed the elstic ehvior up to the reking point. PA66/PP lend hs the highest strin rte. The hyrid effect of the fiers hs reduced the strin rte y 20% thn tht of pure lend. The rnge of strin rte for the rek lod of ll the composites studied is in the rnge of Hyrid effect of Fiers on the Impct Strength nd Hrdness of PA66/PP Blend The individul nd comined effect of short fiers on the impct strength nd hrdness of the lend is shown in Figure 8. The impct strength of pure polylend is 60 KJ/mm 2. Inclusion of 10 wt. % SGF into the lend incresed the impct strength y 8%. Furthermore, the effect of 10% SCF on the sme hs impired the impct strength y 35%. However, the hyrid effect of fiers hd slightly improved the impct strength ove SCF filled one ut elow the impct strength of SGF filled polylend. The decresed impct strength of SCF filled polylend is due to the counterlnce of incresed surfce frcture energy incresed sizes of the voids or SCF ggregtes in the polylend [23]. Influence of hyrid fiers increses the size of the voids nd lso the numer of ggregtes of the short fiers. Glss fier improved the rittle nture of the polylend. This my led to the introduction of voids in the lend nd lso the reinforcement effect initites the crck development in the polymer lend nd therey reducing the impct strength. This will led to the wek reinforcement effect simultneously uilding the strong ridge for the development of internl crck due to the hyrid fier effect. The high impct strength of the polymer lend is due to the effect of PP. The polymer PP modified PA66 requires more energy to rek. This will increse the impct strength of the lend. Hrdness of the polymer lend nd their composites re shown in Figure 8. The hrdness of the polylend Figure 9: Scnning electron microscopy photogrphs of frctured surfce of 10 wt. % short glss fier filled polymide 66/polypropylene lend: () Tensile frcture, () flexurl frcture, nd (c) impct frcture. c 431

8 c Figure 10: Scnning electron microscopy photogrphs of frctured surfce of 10 wt. % short cron fiers filled polymide 66/polypropylene lend: () Tensile frcture, () flexurl frcture, nd (c) impct frcture. c Figure 11: Scnning electron microscopy photogrphs of frctured surfce of 10 wt. % short glss fiers nd 10 wt. % short cron fiers filled polymide 66/polypropylene lend: () Tensile frcture, () flexurl frcture, nd (c) impct frcture. is incresed due to the effect of SGF. This cn explined due to the hrd nture of SGF. Further, slight improvement in hrdness ws noticed due to the SCF effect on the lend. The hyrid effect of the fiers on the hrdness of the polymer lend PA66/PP mrginlly reduces. This cn e ttriuted to the rittle nture of fier filled polymer lend. But the hrdness of the hyrid composite ws retined ove the vlue of the pure lend. Among the studied composites, SGF filled PA66/PP lend composites possess the etter hrdness. 5. FRACTOGRAPHY OF THE SURFACES USING SCANNING ELECTRON MICROSCOPY (SEM) The SEM photogrphs of frctured surfces sujected to tensile, flexure nd impct test of fier filled PA66/PP composites re shown in Figures 9-11, respectively. The SEM microgrphs of frctured surfces of 10% SGF filled PA66/PP lend is shown in Figure 9-c. It is cler from the grph tht SGF filled composites chrcterized y the rittle nture. The fier frcture nd the fier pull out re seen in Figure 9. The sizing of the fiers y the mtrix lend is uniform nd comptile. Less numer of voids ws seen in Figure 9. The flexure frctured surfce of the sme composites is shown in Figure 9. The effective fier-mtrix interfce is seen in the grph. However, the mtrix lend seemed to e strined much. More numer of fier ggregtes is seen in the picture. This is the evidence for the fier frcture. More numer of fier mislignment ws seen from the picture. The fier pull-out is evidenced during the impct ehvior of composites. This is shown in Figure 9c, nd severe mtrix deformtion is lso seen in Figure 9. The sme oservtion ws mde with the SCF filled composites (Figure 10-c). However, the fier pull-out is more during the tension test. The impression of the fier pull out is clerly visile in the SEM picture (Figure 10). The fiers re misligned during the flexure test (Figure 10). But the interfcil onding etween the mtrix nd the fier seemed to very good. Moreover, the uniform sizing of SCF y the epoxy mde the interction effective etween the lends ssocite. There is physicl interction etween the SCF nd lend during the melt lending process. The impct ehvior shows the uniform onding etween the fiers. This is very clerly evidenced in Figure 10c. However, the phse morphology shows tht the crystllinity of the lend is more. This will introduce more numer of voids nd hence less impct strength. The SEM photogrphs of frctured surfces of hyrid composites re shown in Figure 11-c. The tensile frcture is chrcterized y the rittle frcture with the vilility of the voids (Figure 11). Fier fcture nd fier pull-out is evidenced from the photogrph. The severe mtrix deformtion ws exhiited y the photogrph. The impression of fier pull-out from the mtrix is more. This shows the effective onding etween the fiers nd the mtrix. The ending frctured surfces exhiits fier frcture, fier mislignment, nd fiers pull out (Figure 11). However, the ggregtes of SGF nd SCF re more 432

9 due to the fier filure. The ending frcture occurred due to rittle frcture. The mtrix lend seemed to e more strined thn the fiers. The impct surfces of the hyrid composites chrcterized y the rittle filure (Figure 11c). Furthermore, the inner crck initition y the fiers is seen in Figure 11. On the conclusion, the hyrid composites re chrcterized y the rittle frcture which is evidenced y the SEM photogrphs. 6. CONCLUSIONS The effect of lend composition with the hyrid fiers is most promising composites for the etter mechnicl components. The following re the fcts emerged from the experimentl investigtion of hyrid composites. 1. The hyrid composites with 10 wt. % SGF nd 10 wt. % SCF in 80/20 wt. % PA66/PP lend re the promising composites for the structurl pplictions. 2. The hyrid effect of fiers on the tensile strength of composite is most pprecile. It is 70.3 N/mm 2 which is lmost 77% increse over the net lend PA66/PP. 3. The mximum reduction in elongtion ws otined for SCF filled PA66/PP composites. 4. The reinforcement effect of fiers shifted the pek lod to higher vlue which is 56, 62 nd 77% higher thn tht of net lend for SCF, SGF nd hyrid fier filled PA66/PP composites, respectively. 5. The specific strength of the hyrid composite is high. This is due to the high strength of the hyrid fiers. 6. The flexurl strength is improved y 104% over the lend y the hyrid effect of fiers. 7. The significnt improvement over the flexurl modulus ws noticed y reinforcing the fiers into the lend. The flexurl modulus ws improved y 3 times thn tht of the net lend y reinforcing SCF into the lend. 8. The hyrid effect of the fiers hs reduced the strin rte y 20% thn tht of pure lend during ending. 9. Inclusion of 10 wt. % SGF into the lend improved the impct strength y 8%. The effect of 10% SCF on the sme hs impired the impct strength y 35%. 10. The hrdness of the polylend is incresed due to the effect of SGF. Slight increse in hrdness ws noticed due to the SCF effect on the lend. The hyrid effect of the fiers on the hrdness of the polymer lend PA66/PP still reduces. This cn e ttriuted to the rittle nture of fier filled polymer lend. 11. Fier frcture, fier pullout, nd fier mislignment re some of the mechnisms oserved during frctogrphic nlysis through SEM. 7. REFERENCES 1. Z. Chen, X. Liu, T. Li, R. Lu, (2006) Mechnicl nd triologicl properties of PA66/PPS lend. II filled with PTFE, Journl of Applied Polymer Science, 101: M. Pliyik, S. Bhdur, (2000) Mechnicl nd triologicl properties of polymide 6 nd high density polyethylene polylends with nd without comptiilizer, Wer, 246: Mnoj Kumr, S. Rkesh Kumr, H. Shekhr, P. Poomli, (2013) Studies on nn fier reinforced high density polyethylene/ polymide66 lend composites, Journl of Food Technology, 1(4): S. Bhdur, Y. Cheng, (1990) Mechnicl nd triologicl ehviour of polyester reinforced with short glss fiers, Wer, 137: J. Hrtikinen, P. Hine, J. S. Szo, M. Linder, T. Hrmi, R. A. Duckett, K. Friedrich, (2005) Polypropylene hyrid composites reinforced with long glss fiers nd prticulte filler, Composite Science nd Technology, 65: M. Run, X. Li, H. Song, Z. Wng, (2010) Studies on the morphologicl, rheologicl, electricl, mechnicl nd therml properties of PTT/SCF composites, Journl of Thermoplstic Composite Mterils, 23: M. Run, H. S. Wng, X. Li, (2012) Morphology, mechnicl, rheologicl nd therml properties of PTT/ABS/SCF composites, Composite Interfce, 19: S. Y. Fu, B. Luke, E. Mder, C. Y. Yue, X. Hu, (2000) Tensile properties of short glss fier nd short cron fier reinforced polypropylene composites, Composites, 31: Q. Yun, S. A. Btemn, S. Shen, C. Glori-Esprz, K. Xi, (2011) High electricl conductivity nd elstic modulus composites comprising glss fier reinforced cron-filled HDPE, Journl of Thermoplstic Composite Mterils, 26(1): E. C. Botelho, L. Figiel, M. C. Rezende, B. Luke, (2003) Mechnicl ehviour of cron fier reinforced polymide composites, Composite Science nd Technology, 63: H. Shu, A. Rout, A. Kumr, (2012) Development nd chrcteriztion of prticulte filled glss fier reinforced hyrid composites, Interntionl Journl of Mechnicl nd Industril Engineering, 20(3): M. Pliyik, S. Bhdur, (2002) Triologicl studies of polymide6 nd high density polyethylene lends filled with PTFE nd copper oxide nd reinforced with short glss fiers, Wer, 253: T. Yuqin, H. Junlong, (2012) The mechnicl nd triologicl properties of cron reinforced POM composites, Journl of Applied Mechnics of Mterils, :

10 14. Z. Chen, X. Liu, R. Lu, T. S. Li, (2007) Friction nd wer mechnism PA66/PPS lend reinforced with cron fier, Journl of Applied Polymer Science, 105: Z. Chen, X. Liu, R. Lu, T. S. Li, (2006) Mechnicl nd triologicl properties of PA66/PPS lend reinforced with glss fier, Journl of Applied Polymer Science, 102: A. K. Gullu, A. Ozdemir, E. Ozdemir, (2006) Experimentl investigtion on the effect of glss fiers on the mechnicl properties of polypropylene nd polymid6, Mterils nd Design, 27: L. I. Jin, S. To, (2012) The mechnicl nd triologicl properties of CF/PPS composite filled with PA6, Journl of Thermoplstic Composite Mterils, 2: S. Co, H. Liu, S. Ge, G. Wu, (2011) Mechnicl nd triologicl ehviors of UHMWPE composites filled with slt fiers, Journl of Reinforced Thermoplstic Composites, 30(4): S. Zhou, Q. Zhng, C. Wu, J. Hung, (2013) Effect of cron fier reinforcement on the mechnicl nd triologicl properties polymide6/ polyphenylene sulphide, Mterils nd Design, 44: S. H. Wu, F. Y. Wng, C. Chi, M. M, W. C. Chng, C. T. Kuo, H. C. Kun, W. J. Chen, (2001) Mechnicl, therml nd morphologicl properties of glss fier nd cron fier reinforced polymide6 nd polymide66/cly nno composites, Mteril Letters, 49: B. Mouhmid, A. Imd, N. Benseddiq, S. Benmedkhene, A. Mzouz, (2006) Study of the mechnicl ehviour of glss fier reinforced polymid66, Polymer Testing, 25: B. M. Rudresh, B. N. Rvi Kumr, (2016) Effect of SGF loding on the mechnicl ehvior of PA66/ PTFE lend, Trnsctions of The Indin Institute of Metls, DOI: /s N. Y. Ji, V. A. Kgn, (1998) Effects of time nd temperture on the tension-tension ftigue ehviour of short fier reinforced polymides, Polymer Composites, 19: *Biliogrphicl Sketch Dr. B N Rvi Kumr otined his chelor degree in Mechnicl Engineering nd Mster Degree in Mechnicl Engineering specilized in Mchine design from Bnglore University in the yer 1985 nd 1990, respectively. He otined his Ph. D. Degree from Visvesvry Technologicl University (VTU), Belgvi, Krntk, in the field of polymer composites in the yer He hs guided more thn 30 PG projects in mchine design for students of the Progrmme M. Tech in Mchine Design. He hs rich experience of more thn 25 yers in the field of teching. His field of interest includes frcture mechnics, FEM, design of mchine elements, experimentl stress nlysis nd polymer composites. He hs pulished more thn 25 journls in ntionl nd interntionl repute. Presently he is working s Professor in Mechnicl Engineering for Bnglore Institute of Technology, Bengluru , ffilited to VTU, Belgvi, Krntk, Indi 434