短炭素繊維強化PPS樹脂中の疲労き裂進展に対する異方性破壊力学によるアプローチ

抄録

The influence of fiber orientation on the crack propagation behavior was studied with single edge-notched specimens which were cut from an injection-molded plate (IMP) of short carbon-fiber reinforced polyphenylene sulfide (PPS) at two fiber angles relative to the molding direction, i.e. θ = 0° (MD) and 90° (TD). Specimens made of only shell layer of IMP and of only PPS were also produced. The finite element method based on anisotropic elasticity was used to determine the stress intensity factor, energy release rate, and crack-tip opening parameter as crack driving forces. The macroscopic crack propagation path was perpendicular to the loading axis in MD and TD, showing mode I propagation. Microscopically, for MD, the crack was blocked by fibers and circumvented fibers along interfaces, showing a zigzag path. For TD, the crack path was less tortuous following the fiber direction. When the crack propagation rate, da/dN, was correlated to the range of stress intensity factor ΔK, da/dN was lowest for MD and highest for PPS. The core layer in TD of IMP retarded crack propagation in the shell layer. Difference among MD, TD and PPS became small when da/dN was correlated to a parameter corresponding the crack-tip-opening radius, HΔG, where H was a compliance parameter. Strictly speaking, da/dN was lowest for MD, highest for TD, and PPS in between. Fibers perpendicular to the crack direction block crack propagation, while parallel fibers provide preferential crack paths.