TENSILE DEFORMATION BEHAVIOR OF EPOXY COMPOSITES REINFORCED WITH THREE DIFFERENT WOVEN FABRICS.

Mazen, A. A.; Metwalli, M. A.; El-Mahallawy, N. A.

doi:10.21608/asat.2007.23993

TENSILE DEFORMATION BEHAVIOR OF EPOXY COMPOSITES REINFORCED WITH THREE DIFFERENT WOVEN FABRICS.

Document Type : Original Article

Authors

¹ Associate Professor, Faculty of Engineering, El-Menia University, El-Menia, Egypt.

² Graduate Student, Ain Shams University.

³ Professor, Faculty of Engineering, Ain Shams University, Cairo, Egypt.

10.21608/asat.2007.23993

Abstract

The tensile deformation behavior of epoxy matrix composites fabricated by the hand lay-up technique was investigated. Three different types of woven fabrics were used as reinforcements, namely: glass fibers (GF), carbon Fibers (CF), and hybrid reinforcement made of carbon and glass fibers. Four different volume fractions of GF were used, i.e., 9.2 vol. %, 18.4 vol.%, 27.6 vol. %, and 36.8 vol.%. Carbon and hybrid reinforcements were used at a volume fraction of 36.8% each. Besides, specimens of pure (unreinforced) epoxy were tested as a reference material. It was found that increasing the GF volume fraction produced significant improvement in all mechanical properties of the epoxy matrix. The fracture stress of the composite with 36.8 vol.% GF is 375% that of pure epoxy. The composite with 36.8 vol.% CF showed a remarkable 780% increase in fracture stress compared to that of pure epoxy. The hybrid composite (HC) showed an improvement of 590% over the fracture stress of pure epoxy. Similar pattern was followed by other mechanical properties as will be discussed in detail. The rule of mixtures (ROM) and the Halpin-Tsai (H-T) equations were used to analyse the obtained experimental results. It was found that the ROM gives an upper bound for the results with large differences between calculated and experimentally determined parameters. On the other hand, fracture stress values calculated according to H-T equations were so close to experimentally determined ones for all considered volume fractions. Values of elastic moduli calculated according to H-T equations diverted away from experimentally determined ones as the fiber volume fraction increased. Failure and fracture of the composites were investigated both macroscopically and microscopically. Fiber pull-out played a major role in the fracture of epoxy-GF composites. Interlaminar shear failure was found to be the dominant mechanism for fracture of CF composites. Hybrid composites showed a mixed mechanism. These fractographic results proved to be in good agreement with the mechanical testing results.

Keywords