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Role of silicon carbide in glass fiber reinforced composites

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https://www.eduzhai.net International Journal of Composite M aterials 2012, 2(5): 92-96 DOI: 10.5923/j.cmaterials.20120205.04 The Effect ofSilicon CarbideAddition into Fibreglass Reinforced Composites Júlio César dos Santos*, Rubens Bagni Torres, Luciano Machado Gomes Vieira, Zé lia Maria Ve lloso Missagia, André Luis Christoforo, Túlio Hallak Panze ra Departmentof M echanical Engineering, Federal University of SãoJoão delRei (UFSJ), São João del-Rei, 36.307-352, Brazil Abstract In today’s modern world the composite materials have been widely used not only for aerospace/aeronautics, but also automotive, sports and construction industries. The flexural strength of laminated composites depends on the characteristics of dispersive and matrix phases, considering the presence of tensile and co mpressive loadings. For this reason, the addition of particles into the matrix phase has been investigated to enhance its stiffness and consequently the elastic modulus of the composite. Th is work investigates a glassfibre co mposite reinforced with silicon carbide part icles. The following responses were evaluated: apparent density, water absorption, flexural strength, modulus of elasticity. The results were compared to those manufactured with no silicon carbide particles. It was observed that the silicon carbide particles provided the increase of the apparent density and flexu ral strength of the composites. Keywords Laminated Co mposites, Silicon Carbide, Fibre Glass, Hybrid Co mposites 1. Introduction The growing demand of co mposite materials has increased the attention to the theories of reinforced materials and advanced processes for their production. Some industrial sectors, as the areas of missiles, rockets and aircraft, owned the restricted use of structural poly meric materials or advanced polymeric materials. Following decades of restrict ion, modern industries have expanded the use of these materials. The automotive, sports and construction industries[1,2] have experienced an increase of this technology every year due to their superior specific strength, lower density, higher corrosion resistance and high strength/modulus over conventional materials[3,4]. Replacement o f metals by co mposites in co mmercial aircraft prime structures has been rapidly increasing to achieve further structural weight saving and reduce fuel consumption with a background of g lobally soaring oil p rices [3] . Bra zil has e xpanded their e xpe rience of innovation in the application of structural co mposites, especially in the aeronautics sector, using for external and internal planes/ helicopters (about 20% of the area of an aircraft) and a lesser extent for structure of rockets[3]. The dynamic flexu ral loadings in aircraft fuselage must be cons idered in th e st ruct u ral d es ign . In th is case, t he * Corresponding author: juliosantosjcs@hotmail.com(Júlio Cesar dos Santos) Published online at https://www.eduzhai.net Copyright © 2012 Scientific & Academic Publishing. All Rights Reserved composites must provide high stiffness and fatigueresistance[5, 6]. The modification of the mechanical behavior of poly mers by the addition of filler materials have shown a great importance in researches and has lately been a subject of considerable interest[7,8]. In order to increase the flexural modulus of laminated composites, ceramic particles have been added in the matrix phase to enhance the mechanical performance of laminated composites. Flexural strength of laminated composites can be improved with ceramic particles[9]. Silicon carbide (SiC) particles can improve thermal responses of poly mers[10] and some mechanical responses[11] of laminates. This work investigates the physic-mechanical properties of hybrid poly meric co mposites reinforced with glass fib re and silicon carbide particles. The fatigue resistance and therma l properties will be the scope of future investigations. 2. Materials and Methods 2.1. Epoxy Resin The epoxy resin was supplied by M/s. Alpha Resiqualy Co mpany (São Paulo, Brazil). The addition of 66.66% of resin (RQ-0100RF) with 33.34% of hardening agent (RQ-0164RF PLUS) was mixed to obtain the matrix phase. 2.2. Reinforcements Phases The glassfibre fabric of 240 g/ m2 was used in this experiment. The silicon carbide particles were supplied by M/s. Saint Gobain Co mpany (Barbacena, Brazil) with 93 International Journal of Composite M aterials 2012, 2(5): 92-96 particle size between mesh 200-325. 2.3. Experi mental Condi tions The glass fibre reinfo rced composites were investigated by the use of matrix phase non-modified and modified with silicon carb ide particles. 2.4. Manufacture The specimens were fabricated by hand-lay-up process[12] according to the recommendations of Vison and Sierakowski[13] (Fig. 1). For this research, the silicon carbide part icles were sieved in mesh 200 - 325 US-Ty ler (the part icles retained on 325 US Tyler, were used). By volu me percent, the composite was shared in 30% of reinforced phase and 70% ofmatrix phase. Three layers of glass fibre were cut into squares of 200 x 150 mm. Then, the mass of fibre was measured and the fibre volume ( Vf ) of co mposite was calculated according eqn. 1: Vf = mf /ρf (1) Where mf is the mass of fibre and ρf (2,5 g/cm3) is the density of fibre. According eqn. 2, the volume of matrix ( Vm )was obtained: Vm = (Vf × 70)/30 (2) After, by density of matrix ρm (1,16 g/cm3), the matrix mass (mm) was obtained according eqn. 3: m m = Vm × ρ m (3) Figure 1. Hand lay-up method The weight of particles mass was based in 20 wt.% (this amount was based in results of[14]). The silicon carbide particles were mixed into epoxy resin matrix, manually. Later, the matrix reinforced with particles, was used for laminating of the three layers of glass fibre. The Armalon® demoulding sheets were used at the bottom and upper surfaces in order to ensure a goodsurface fin ish,as shown in Fig. 2. The samples were cured under room temperature, under 20 Newtons of uniaxial co mpressive forces, for 7 days. 2.5. Methodol ogy 2.5.1. Relative density The apparent density was obtained according to ASTM SD792[15]. Test method a for testing solid plastics in water was used. By eqn. 4 was possible to calculate the relative density (rd) of samp le: rd = a (a + w − b) (4) Where: a (apparent mass of specimen, without wire or sinker in air), b (apparent mass of comp letely immersed and of the wire partially immersed in liquid) and w (apparent mass of totally immersedand of partially immersed wire)[15]. 2.5.2. Water Absorption The water absorption was measured according to ASTM D570[16]. The specimens were immersed in saturated distilled water for 24 hours at 23ºC. The water absorption was calculated as fo llo ws : % = wet weight − cond.weight ×100 cond.weight (5) Conditioned weight: is the mass of sample immersed in water. The percentage of soluble matter lost during immersion, was determined by using the eqn.6. % = cond.weight − recond.weight ×100 cond.weight (6) Recond. weight: mass of sample reconditioned in water after removal of there. The percentage of water absorption was calculated dividing eqn.1 by eqn.2. Figure 2. Silicon Carbide addition 2.5.3. Flexural Stress The samples were prepared according to ASTM D790[17], based on the recommendations of materials less than 1.6mm in thickness. The flexu ral strength was calculated by Eqn. 7. σ f = 3PL 2bd 2 (7) Where P is the load at a g iven point of load-deflection curve, L (25,4 mm) is the support span, b (12,7 mm) is the width and d (mean of 1,28) is the depth of beam tes ted. Júlio César dos Santos et al.: The Effect ofSilicon CarbideAddition into Fibreglass Reinforced Composites 94 2.5.4. Modulus of Elasticity The modulus was obtained by the tangent modulus of elasticity in the ASTM D790 as follows: E B = (L3 m) (4bd 3 ) (8) Where L (25,4 mm) is the support span, b (12,7 mm) is the width of beam tested, d (mean of 1,28 mm) is the depth of beam tested and m (calcu lated by graphic) is the slope of the tangent modulus (obtained by 50% deflection relative of the maximu m flexu ral strength force). by the “t tabulated data”, then the initial hypothesis (Ho) is rejected[18]. 3.1. Relati ve Density The apparent density values of the composites varied from 1.50 to 1.63g/cm3. Fig. 3 shows the density graph for both conditions. The addition of siliconcarbide particles leads to an increase of 4.15% in apparent density of the material. This behavior was expected due to the higher density of silicon carbide particles. 3. Results The comparisons between the results were carried out based on the Hypothesis Test for Difference of Means with Unknown Variances[18]. Th is analysis is able to verify whether the factor significant affects the response variables. The statistical analysis was performed for the flexu ral strength and modulus of elasticity responses. The other responses were analyzed based on the average and standard deviation of the e xperimental results. Table 1 shows the means and standard deviations for each response variable. Figure 3. Graphic for Relative density Table 1. Means and st andard deviat ions Variable Response Relative den sit y W at er abso rpt ion Flexural stress Modulus Elast icity Without Particles Mean 1.56 SD 0.096 5.83 50.86 0.056 5.27 6.65 0.77 With particles Mean 1.63 SD 0.005 2.69 73.0806 0.008 9.63 6.63 0.44 3.2. Water Absorption The water absorption values of the composites decreased fro m 1.89% to 0,98%. Fig. 4 shows the water absorption graph for both conditions. The silicon carb ide addition provided the reduction of 45.97% on the water absorption of the co mposites. Like the research of[11], one barrier properties appears, by the high loading of silicon carbide, covering the fibres. This layer of particles under the fibres, pro moted a decrease of water absorption. Table 2 gives the amounts for the hypothesis test for two averages. The confidence of 95% was set, wh ich corresponds to an α =level of 5%. Table 2. Test : Hypot hesis t est V. R. Hyp. t calc t tab Concl. Relative Density Flexural st ren gth Flexural modulus H0: µ1= µ2 H0: µ1> µ2 H0: µ1= µ2 H0: µ1> µ2 H0: µ1= µ2 H0: µ1> µ2 6,52 1,81 Reject H0 4,52 1,81 Reject H0 0,048 1,81 Accept H0 The comparison was performed between two means based on the t-student distribution, calculating the value o f the “t calculed” and comparing with “t tabulated”. When the value of “t calcu lated” is outside the region of acceptance covered Figure 4. Graphic for Water absorption 3.3. Flexural Strength The flexural strength data of the composites varied fro m 50,86 to 73,08 M Pa. Based on the hypothesis test, the flexural strength was significantly affected by the addition of silicon carbide particles, exh ibiting a rate of gro wingof 43,7%. Fig. 5 shows the increase in fle xura l strength. 95 International Journal of Composite M aterials 2012, 2(5): 92-96 shown in Table 1. Based on the Table 2, the two means are statistically the same (Table 2). For this reason, it is concluded the particle addition d id not affect this response. Fig. 6 shows the increase in modulus of elas ticity . The modulus did not affected by poor dispersion the particles into de epoxy matrix. Regions without particles in matrix phase can be observed (fig. 7). For improve the modulus, a good dipersion of particles, should be promoted. Figure 5. Graphic for Flexural Strength The idea behind the increase is due the h igh silicon carb ide particles density, then the particles were decanted (fig. 3) under glass fibre, then, accord ing some argu ments shown by[9] in his rev iew, a fib re surface coating occurred. The particles pro moted an increased in the roughening the fiber– matrix interface affecting the bonding strength between both, causing an increase in the shear stress transfer at the interface, co llaborate to increase the flexu ral s tren gth [9]. 4. Conclusions The addition of micron silicon carbide particles provided the increase of apparent density and the reduction of water absorption of the co mposites. The addition of part icles increased the flexural strength; however the modulus of elasticity was not significantly affected. REFERENCES 3.4. Modul us of El asticity [1] M . S. Issa, I.M . M etwally, S. M . Elzeiny. “Influence of fibers on flexural behavior and ductility of concrete beams reinforced with GFRP rebars”, Engineering Structures, Volume 33, pp 1754-1763, 2011. [2] P. J. D. M endes, J. A.O. Barros, J. M . Sena-Cruz. M . Taheri. “Development of a pedestrian bridge with GFRP profiles and fiber reinforced self-compacting concrete deck”, Composite Structures, Vol. 93, pp 2969-2982, 2011. [3] M . C. Rezende. “O Uso de Compósitos Estruturais na Indústria Aeroespacial.” Polímeros: Ciência e Tecnologia, vol 10, nº 2, 2000. Figure 6. Increase of Modulus of Elasticity [4] D. Qian, L. Bao, M . Takatera, K. Kemmochi, A. 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SEM - Agglomerates of silicon carbide particles in the inferior region of polymer The modulus of elasticity varied fro m 6.65 to 6.63 GPa. The mean and standard deviation for each condition are [8] V. Fiore, F. Alagna, G. Galtieri, C. Borsellino, G. Di Bella, A. Valenza. “Effect of curing time on the performances of hybrid/mixed joints.” Composites Part B: Engineer ing, ISSN 1359-8368. 2012. [9] Y. Cao, J. Cameron. “Flexural and Shear Properties of Silica Particle M odified Glass Fiber Reinforced Epoxy Composite.” Júlio César dos Santos et al.: The Effect ofSilicon CarbideAddition into Fibreglass Reinforced Composites 96 Journal of Reinforced Plastics and Composites.2006; 25; 347originally published online Aug 16, 2005.DOI: 10.1177/0731684405056450. fibres and silica microparticles”. Composites Part B: Engineering, Available online 9 January 2012, ISSN 1359-8368, 10.1016/j.compositesb.2012.01.026. [10] R. M . Rodgers, H. M ahfuz, V. K. Rangari, N. Chisholm, S. Jeelani. “Infusion od SiC Nanoparticles Into SC-15 Epoxy: Na Investigation of Thermal and M echanical Response.” M acromolecular M aterials and Engineering. 2005, 290, 423-429. 2005. [11] H. Alamri, I.M . Low. “Effect of water absorption on the mechanical properties of n-SiC filled recycled cellulose fibre reinforced epoxy eco-nanocomposites”. Polymer Testing, Volume 31, Issue 6, PP 810-818, ISSN 0142-9418, 2012. [12] E. Sevkat, M . Brahimi. “The bearing strength of pin loaded woven composites manufactured by vacuum assisted resin transfer moulding and hand lay-up techniques”. Procedia Engineering, Volume 10, pp 153-158, 2011. [15] ASTM Standard D792, 2008. “Test M ethods for Density and Specific Gravity (Relative Density) of Plastics by Displacement,” ASTM International, West Conshohocken, PA, 2008, DOI: 10.1520/D0792-08, www.astm.org. [16] ASTM Standard D570, 1998 (2010). “Test M ethod for Water Absorption of Plastics,” ASTM International, West Conshohocken, PA, 2010, DOI: 10.1520/D0570-98R10E01, www.astm.org. [17] ASTM Standard D790, 2010. “Test M ethods for flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating M aterials,” ASTM International, West Conshohocken, PA, 2010, DOI: 10.1520/D0790-10, www.astm.org. [13] J. R. Vison, R. L. Sierakowski. “The Behavior of Structures [18] D. C. M ontgomerry, G. C. Runger. “Estatística aplicada e Composed of CompositeM aterials.” 2 ed. Nem York: Kluwer probabilidade para engenheiros.” 4. ed. Rio de Janeiro: LTC, Academic Publishers, pp 16-17, 2002. pp 208-217. 2009. [14] L. J. da Silva, T. H. Panzera, V. R. Velloso, A. L. Christoforo, F. Scarpa.“Hybrid polymeric composites reinforced with sisal

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