IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 The Mechanical Properties of Laminated Composites Reinforced With Discontinuous and Continuous Different Fibers M. A. AL-Nesearawi Department of Physics, College of Education I bn Al-Haitham, Unive rsity of Baghdad Abstract In this p aper we invest igate how do the laminated comp osites behave mechanically when subjected to external st resses, when reinforced with continuous fibers (mat) and discontinuous fibers (chopped) and to find the effect of the fiber type on the mechanical p rop erties. Laminated comp osites consisting of wood- wood and Ph-F resin as suitable adhesive were r einforced with different fibers(jute, glass, and carbon).However, two different methods of reinforcement namely , mat and chopp ed fibers were utilized. The mechanical p rop erties such as (imp act st rength, comp ression strength, tensile strength, shear strength, bending st rength, and elasticity modulus) of laminated comp osites were measured. Fib ers reinfor ced laminated composite exh ibited bett er mechan ical p rop erties than anreinforced composite. Furthermore, Carbon fibers reinforced laminated comp osite exh ibited b ett er mechan ical p rop erties than both jute and glass fibers reinforced composite. All used fibers of laminated comp osite showed that distribution as mat rather than as chopp ed, where the increase in the total st rength of laminated comp osite was observed as mat. Introduction Lay ered comp osites are found in many familiar app lications. Ply wood comp osite is usually made from thin layers of wood with a suitable thermosetting resin as adhesive. The lay ers of wood p rovide the bulk of the st rength, while the resin acts as a semi-rigid binder[1]. As a result, laminates formed from bonding lay ers of wood by organic adhesive exhibit distinctive p rop erties from these of the individual p ly (lamina) that its usually used for makin the comp osite. Laminates such as metal to metal, metal to ceramic, metal to p olymer, p olymer to p olymer, ceramic to p olymer, ceramic to ceramic are also good examp les of laminated comp osites[2].Adhesion is the interaction between the two different subst rates across an interface which may involve either p hy sical or chemical bonding. Chemical bonding consists of direct interlinking between molecules by covalent or ionic bonds. The p hy sical bonding may result from mechanical interlocking or from the forces of p hy sical adsorp tion between adhesive molecules and substrate molecules, or by the p enetration of adhesive molecules into subst rate by diffusion. Thus, the mechanism of adhesive action is quite different according to the ty p e of reaction[3].The advantage of fiber reinforcement is two-fold: i- enhancement of the mechanical p rop erties such as st rength, st iffness and heat deflection temp erature, ii- increase of the toughness of the matrix, so that more energy is required to initiate and p rop agate fracture[4]. In the fibers reinforced materials, the stress is carried almost entirely by the fibers and the matrix is used to 1- bind the fibers t ogether (by cohesion and adhesion),2-transmit t he stress from one fiber to the other(dist ributes load evenly among fibers),3-p rovides resistance for a comp osite to crack p rop agation,4- p rotect the fibers from the environment,5- keep reinforcing fibers in a desired orientation[5]. However, we must consider the factors in the design of fibers reinforced comp osites. They are the asp ect ratio, volume fraction, ty p e of fiber( metallic, glass, carbon, IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 ceramic, p olymer, and whisker ) ,critical length for chopp ed fibers, and the method of reinforcement. It may be classified as continuous fibers along the matrix , orthogonal fibers, mat (in which the continuous fibers are distributed equally along the matrix longitudinally and transversely to give the form of mat or net), and chopp ed fibers (discontinuous) [6]. M any researches st udied the effect of adhesive on the mechanical p rop erties for laminated comp osites[7,8,9]. The aim of using the resin as a binder among thin lay ers is to p roduce laminated comp osites with a high st rength. So we seek to increase st rength of these sy st ems via the reinforcement with fibers and better choice of fiber ty p e and distribution within the resin. In a p revious article [10] we reported the effect of continuous fibers distribution regarding (length, width, orthogonal, and mat) method, on the mechanical p rop erties for laminated comp osites by using glass fibers. It was found that fibers reinforced laminated comp osites exhibit bett er mechanical p rop erties than anreinforced comp osites. Furt hermore, the increase in the total st rength of laminated comp osite was observed as mat. This p aper aiming to comp are the mat (continuous fibers) with chopp ed (discontinuous fibers) and effect of fiber ty p e through choosing three fibers(jute, glass, and carbon) on the mechanical p rop erties such as imp act st rength, comp ression st rength, tensile strength, shear strength, bending st rength, and elast icity modulus of laminated comp osite. Experime ntal We have p repared and test ed 42 samp les of laminated composites reinforced by jute, glass, and carbon fibers with 22wt % .They were manually distributed on adhesive by two methods (chopp ed and mat) .Laminated comp osites consisting of wood-wood and resin reinforced with fibers were p repared in p olymer searches unit, College of Science ,University Al-mustansiriy a through many st eps.T he first was st arted with p utting the solvent ethanol (15ml) in flask to dissolve Ph-F(p henol-formaldehy de)resin by using water bath at controlled temp erature (70 o C). The reaction was st irred and heated for 30min until the solution becomes t urbid and then adding the bonding sy st em (talk p owder 8%), Hexamethy letetraamine( H.M TA. 10%), and resorcinol(4%). Finally we fix Ph-F resin reinforced by jute, glass, and carbon fibers between wood surface of various dimensions. The prepared samples were heated at 120 o C under pressure to obtain the final solid p roduct .For the invest igation of st ructure of laminated comp osites, we st udied the microstructure of the p repared sp ecimens by the op tical microscope of the ty p e (Oly mpus).T he micrographs of p olishing surface texture of anreinforced and reinforced laminated comp osites are shown in Figs.(1,2,3) by using images analysis with soft ware of ty p e VCIA,G,version 4.81. Charpy imp act instrument was used for imp act test ,where the samples are p rep ared with dimensions 10 x10 x55mm according to (ISO-179). Hy draulic p iston type Ley bold Harris No.36110 was used to measure the comp ressive strength of samples at room temp erature . ASTM -D695 method was used for the p rep aration of the samples with the length double the width to obtain the ratio 2:1 and the thickness was equ al to its width. Bending test of rectangular samples with dimensions of (10x135mm)was carried out accordin g to ASTM -D790. Tensile st rength , modulus of elasticity ,and shear st rength were determined by Zweigle instrument accordin g to ASTM -D648, where the crosshead sp eed was 5mm/min at room temp erature. These testes are carried out in p hy sics laboratory , Dep artment of App lied Sciences, University of Technology . IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 Results and Discussion The resultant mechanical p rop erties of the (st andard) anreinforced and reinforced laminated comp osites are showed in f igures(4-15). Three different ty p es of fibers were used to st udy the effect of fiber ty p e. Figs.(4-9) show the p lots of imp act st rength, comp ression st rength, tensile st rength, shear strength, bending st rength, and elasticity modulus of the (jute,glass,carbon) fibers reinforced and st andard comp osites versus fibers distribution. Where the sy mbols (s, ch, m ), indicates; standard, chopp ed, and mat r esp ectively. It is observed that as mat gives better results comp ared with chopped way through increasing of imp act, comp ression, tensile, shear st rength, and elast icity modulus as shown in Figs.(4-8) due to the fibers which form mat carry and transmit the stress together to p roduce higher modulus and high er ener gy absorption for the comp osite while random (chopp ed) fibers p roduce lower modulus and low energy absorption for the comp osite . Also It is observed the decr ease of deflection and then the increase of bendin g st rength of comp osite are due to t he reinforcin g fibers, sp ecifically as mat with carbon fibers as illustrated in Fig.(9). M oreover, Figs.(4-9) ensure that the p resence of the reinforcing fibers would st rengthen the comp osite. After choosing mat as an alternative method we have studied the effect of t yp e of the fiber through the results showed in Figs(10-15) where the carbon fibers gave more st rength of the mechan ical p rop erties of the laminated comp osites comp ared to glass and jute fibers because of the carbon fibers hav e higher modulus compared to glass and jute fibers . Conclusions The exp erimental results give rise to the conclusion that laminated composites reinforced with continuous fibers, as mat, exhibit bett er mechanical p rop erties than discontinuous chopp ed fibers .Also the fiber typ e affects the mechanical p rop erties of laminated comp osites, where carbon fibers gave better strength than others fibers (glass and jute). Re ferences 1- Eckold, G.,(2000) “Design and M anufacture of Composite Structure”,(3 rd ed),pp.126- 128,M cGraw-Hill Inc., En gland. 2- Gray son ,M. (1983) “ Ency clop edia of Comp osite M aterials”,(3 rd ed),John-Wiley, New York. 3- Skeist ,I. (1990) “Hand Book of Adhesive”,(3 rd ed) ,pp.41-46,Krieger, New York. 4- Pisharath, S. and Wong, S.C. (2001) , J.M ater.Process.Tech., 113:167-171. 5- Gupt a, R.B. (1979) “M aterials Science and Processes”,(4 th ed)., pp .529-534, Saty a Prakashan,India. 6- Craig, M .C. and Daniel, F.C. (1999) J.Elast.Plas., 31:367-372. 7- At heer, A.A. (2005),“Effect of Bonding on the M echanical Prop erties of Resin as Adhesive for Wood-Wood Surf aces”, M .Sc Thesis, Ba ghdad University , College of Edu cation Ibn al- Haitham. 8-M udhafer, J.A. (2006) “Prep aration Cement Bonding Ceramic-M etal”, M .Sc Thesis, Baghdad University , College of Edu cation Ibn al-Haithem. 9-Ahmed,(2003) “Ability Poly mer As Adhesive For Bonding Iron-Iron”, M .Sc Thesis, Ba ghdad University , College of Edu cation Ibn al-Haithem. 10-M uhammed ,A.A and Atheer, A.A. (2008) Al-M ustansiriy a J.Sci,vol.19(10: 27-34 IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 Fig(1): The optical micrograph(100x) of wood- a dhe si ve - wood Fig.(2): The optical micrograph(100x) of wood- a dhe si ve - wood rei nforced with mat fi bers Fig.(3): The optical micrograph(100x) of wood- a dhe si ve - wood rei nforced with chopped fibers wood wood wood wood wood wood adhesive adhesive fibers fibers adhesive IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 s ch m s ch m s ch m 7 8 9 10 11 12 13 fibers dist ribution Im pa ct s tr en g th (k J/ m 2) Jute Glass Carbon Fig.(4):Effect of fibers distribution on the impact strength. s ch m s ch m s ch m 13 15 17 19 21 fibers distributio n C o m p re ss io n s tr en g th (M p a ) Jute Glass Carbon Fig.(5):Effect of fibers distribution on the compression strength. s ch m s ch m s ch m 16 18 20 22 24 fibers d ist rib ution E la s ti c ity m o d u lu s (M p a ) Jute Glass Carbon Fig.(6):Effect of fibers distribution on the elasti city modulus. IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 s ch m s ch m s ch m 7 11 15 19 fibers distribution T e ns il e s tr e ng th ( M p a ) Jute Glass Carbon Fig.(7):Effect of fibers distribution on the tensile strength. s ch m s ch m s ch m 6 8 10 12 14 16 fibers distrib ution S h e a r s tr es s (M p a ) Jute Glass Carbon Fig.(8):Effect of fibers distribution on the she ar stress. IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 s ch m s ch m s ch m 0.4 0.6 0.8 1 fibers distr ibution D ef le c tio n (c m ) Jute Glass Carbon Fig.(9):Effect of fibers distribution on the deflection at load 250g. 7 9 11 13 standard Jute Glass Carbon Fiber Type Im p a c t S tr en g th (k J /m 2 ) Fig.(10):Effect of fibers type reinforced with mat way on the impact strength.. IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 13 15 17 19 21 standard Jute Glass Carbon Fiber Type C om pr es si on S tr en gt h( M pa ) Fig.(11):Effect of fibers type reinforced with mat way on the compression strength. 16 18 20 22 24 standard Jute Glass Carbon Fiber Type E la s ti c M o d u lu s (M p a ) Fig.(12):Effect of fibers type reinforced with mat way on the elasti city modulus. IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 7 10 13 16 19 standard Jute Glass Carbon Fiber Type T en si le S tr e n g th (M p a ) Fig.(13):Effect of fibers type reinforced with mat way on the tensile strength. 5 8 11 14 standard Jute Glass Carbon Fiber Type S h ea r S tr es s( M p a) Fig.(14):Effect of fibers type reinforced with mat way on the she ar stress. IBN AL- HAITHAM J . FO R PURE & APPL. SC I VO L. 23 (1) 2010 0.3 0.5 0.7 0.9 standard Jute Glass Carbon Fiber Typ e D ef le ct io n (c m ) Fig.(15):Effect of fibers type reinforced with mat way on the deflection at load 250g. 2010) 1( 23مجلة ابن الھیثم للعلوم الصرفة والتطبیقیة المجلد تمرة مس بألیاف مختلفة الخواص المیكانیكیة للمواد المتراكبة الطبقیة المعززة وغیر مستمرة محمد عبدالنبي النصیراوي . ابن الهیثم، جامعة بغداد-قسم الفیزیاء، كلیة التربیة الخالصة في هذا البحث عن التصرف المیكانیكي للمواد المتراكبة الطبقیة المعززة بألیاف مستمرة بطریقة الحصیرة و نتحرى .و ما تأثیر نوع اللیف على الخواص المیكانیكیة .ألیاف متقطعة عندما تخضع للجهود الخارجیة ألیاف :(بألیاف مختلقة مثل امناسب االصق F-һРخشب و الراتینج - عززت المواد المتراكبة الطبقیة المكونة من خشب قیست الخواص المیكانیكیة عززت هذه األلیاف بطریقتي الحصیرة و األلیاف المتقطعة.)و الكاربون،و الزجاج ،الجوت للمواد المتراكبة ) و معامل المرونة مقاومة االنحناء و مقاومة القص و مقاومة الشدو مقاومة االنضغاط و مقاومة الصدمة( الطبقیة وظهر أن الخواص المیكانیكیة للمواد المتراكبة الطبقیة المعززة بأاللیاف أفضل مما للمواد المتراكبة الطبقیة غیر میكانیكیة أفضل من المواد المتراكبة الكاربون أظهرت خواصالمواد المتراكبة الطبقیة المعززة بألیاف ا فضال عن ذلك ةالمعزز ة قي تعزیز المواد المتراكبة بینت أن طریقة الحصیرة أفضل من لمعجمیع األلیاف المست.الطبقیة المعززة بألیاف الجوت و الزجاج ة الطبقیة من خالل الزیادة الملحوظة في المقاومة الكلیة للمواد المتراكب طریقة األلیاف المتقطعة عند استخدام طریقة الحصیرة