Ghafaar, M., Mazen, A., El-Mahallawy, N. (2006). BEHAVIOR OF WOVEN FABRIC REINFORCED EPOXY COMPOSITES UNDER BENDING AND COMPRESSIVE LOADS. JES. Journal of Engineering Sciences, 34(No 2), 453-469. doi: 10.21608/jesaun.2006.110472
M. Abdel Ghafaar; A. A. Mazen; N. A. El-Mahallawy. "BEHAVIOR OF WOVEN FABRIC REINFORCED EPOXY COMPOSITES UNDER BENDING AND COMPRESSIVE LOADS". JES. Journal of Engineering Sciences, 34, No 2, 2006, 453-469. doi: 10.21608/jesaun.2006.110472
Ghafaar, M., Mazen, A., El-Mahallawy, N. (2006). 'BEHAVIOR OF WOVEN FABRIC REINFORCED EPOXY COMPOSITES UNDER BENDING AND COMPRESSIVE LOADS', JES. Journal of Engineering Sciences, 34(No 2), pp. 453-469. doi: 10.21608/jesaun.2006.110472
Ghafaar, M., Mazen, A., El-Mahallawy, N. BEHAVIOR OF WOVEN FABRIC REINFORCED EPOXY COMPOSITES UNDER BENDING AND COMPRESSIVE LOADS. JES. Journal of Engineering Sciences, 2006; 34(No 2): 453-469. doi: 10.21608/jesaun.2006.110472
BEHAVIOR OF WOVEN FABRIC REINFORCED EPOXY COMPOSITES UNDER BENDING AND COMPRESSIVE LOADS
1Design and Production Engineering Department, Faculty of Engineering, Minia University, Minia, Egypt
2Production Engineering Department, Faculty of Engineering, Ain Shams University, Cairo, Egypt
Abstract
The mechanical behavior of epoxy reinforced by three different types of woven fibers was studied under compressive and bending loads. The reinforcements used were: woven glass fibers (volume fractions: 9.2%, 18.4%, 27.6%, and 36.8%), woven carbon fibers, and woven hybrid (carbon/glass) fibers at 36.8 vol.%, each. The composites were manufactured using the hand lay-up technique. Pure (unreinforced) epoxy specimens were tested as a reference material. The fracture behavior of the investigated specimens was studied both macroscopically, and using scanning electron microscopy (SEM). It was found that under compressive loads, elastic deformation is nonlinear for pure epoxy as well as epoxy reinforced by low volume fractions of glass woven fibers. At high volume fractions of glass fibers, carbon fibers, or hybrid ones, this non linearity diminished significantly. The modulus of elasticity of epoxy-reinforced by glass fibers (GF) continued to increase as a function of fiber volume fraction. At 9.2 vol.% the modulus of elasticity showed an increase of 65% compared to pure epoxy, while at 36.8 vol.% GF the improvement reached 117%. At the same volume fraction of 36.8% hybrid, and carbon reinforcements the improvements were 160%, and 178%, respectively. Similar trend of improvements were observed for the other mechanical properties under compressive loads. Under bending loads, both the flexure modulus, and flexure strength showed significant improvement as a function of glass fiber volume fraction. At the same reinforcement volume fraction, carbon fiber composites gave the highest mechanical properties, followed by hybrid composites, while glass fiber composites showed lowest improvement (about 348% improvement in flexure strength compared to pure epoxy). Fiber pull-out and debonding are the main fracture mechanisms for glass fiber reinforced epoxy, while interlaminar shearing is the main mechanism for carbon fiber composites. Hybrid (C/G) composites showed a mixed mode mechanism. The fracture process in bending proceeded in stages from the tension side inwards towards the compression side. Each stage is associated with a load drop and audible sound waves.
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