抄録
The influence of plate thickness on the crack propagation behavior was studied with single edge-notched specimens which were cut from injection-molded plates (IMP) of short-fiber reinforced plastics at three angles of the loading axis relative to the molding flow direction (MFD), i. e. θ=0° (MD), 45°, 90° (TD). Injection molded plates had the thickness of 1 and 4mm, and were called IMP1 and IMP4, respectively. IMP have three layer laminated structure where the core layer was sandwiched by two shell layers. The fiber orientation in the shell layer was parallel to MFD and that of the core layer was nearly perpendicular to MFD. The fraction of the shell layer to the plate thickness was 0.845 for IMP1 and 0.185 for IMP4. In the relation between the crack propagation rate and the stress intensity factor range, ΔK, MD has slower rates than TD and 45° in IMP1, while in IMP4 MD has faster rates. When the crack propagation rate was correlated to ΔK/E, the relations for different orientations merged together in the case of IMP1. On the other hand, in the case of IMP4, the relations didn't merge. Macroscopic crack path was nearly perpendicular to the loading axis for MD and TD with both thicknesses. The crack growth direction of 45° plates of IMP1 was inclined against the loading axis, while that of IMP4 was nearly perpendicular with repeated up-and-down.
