Impact Behavior of Hybrid-Fiber and Hybrid-Matrix Composites

Abstract

Fracture behavior of advanced interlaminar hybrid composites has been investigated. Single-matrix/double-fiber, double-matrix/single-fiber, and double-matrix/ double-fiber hybrids as well as their single-fiber/single-matrix control versions were stud ied. The addition of glass fiber-PPS (polyphenylene sulfide) laminas in graphite fiber-PPS composites was found to be effective in improving the impact resistance of the material. As the percentage of glass fibers increased, so did the maximum load tolerated and impact energies absorbed by the material. The intermixing of glass- and graphite-fiber plies also helped decrease the sudden catastrophic failure mode, which is usually associated with graphite-fiber composites. This was due to the extra strain energy dissipated by massive delamination and the subsequent crack blunting mechanism. Adding thermoplastic PPS fiber laminas in epoxy/graphite fiber plies was also found to enhance the impact energy ab sorption capability of the otherwise brittle thermoset composites. Different extents of delamination and thickness-direction cracking were observed with different combinations of fibers and matrices. In comparison to the epoxy-based composites, the PPS-based materials, with poorer fiber-matrix bonding, generally showed a greater level of interfacial debonding and fiber pull-out. Visual and SEM examination of the double-matrix hybrid samples also showed large amounts of ply- and fiber-matrix debonding. The bonding be tween dissimilar laminas was not as strong as that between similar matrix plies, resulting in excessive delamination. This was confirmed in post-impact three-point bending tests where the damage tolerance of the double-matrix hybrids was inferior to that of the single- matrix composites.