Abstract
The influences of fiber orientation and stress ratio on the crack propagation behavior were studied with single edge-notched specimens which were cut from an injection-molded plate of short fiber reinforced plastics (SFRP), at five fiber angles relative to the loading axis, i.e. θ=0° (MD), 22.5°, 45°, 67.5°, 90°(TD). Macroscopic crack propagation path was nearly perpendicular to the loading axis for case of MD and TD. For the other fiber angles, the crack path angle increased with decreasing fiber angle. In the relation between crack propagation rate and the stress intensity factor range, ΔK, the propagation rate of fatigue cracks was slowest for MD, and increased with increasing fiber angle. When the crack propagation rate was correlated to ΔK/E (Young's modulus), the relations for different orientations merged together. The crack propagation rate was mainly controlled by the maximum stress intensity factor K_<max> at high rates and by stress intensity factor range ΔK at low rates.
