| Research Abstract |
Constant DELTAK fatigue crack propagation tests were conducted with double cantilever baam (DCB) specimens made of two kinds of unidirectional CF/epoxy laminates. The effects of loading frequency, test temperature, and environment on the interlaminar delamination fatigue crack growth were investigated. The effect of cyclic frequency was not observed in air. The effect of test temperature was found to depend on material and environment. The interlaminar fatigue crack propagation rate was lower for higher angle between fiber and crack propagation direction. The rate also depended on specimen width.
Fatigue crack propagation rate accelerated after overloading while it usually decelerates in metallic materials. Crack tip shielding by fiber bridging may diminish (or minimize) by overloading.
In addition to the continuous fiber reinforced plastic mentioned above, stress relaxtion tests of short glass fiber reinforced plastics (GFRP), which is widely employed in engineering products, were conducted to evaluate interfacial shear stress. Based on the visco-elastic model and stress relaxation tests, the effects of surface treatment, strain rate, mixing pressure on tensile and fatigue properties were analyzed.
|
