Abstract
High strength type CF/Epoxy composites have been applied to many aircraft and spacecraft structures. The composite laminate, however, has week point at interlamina strength. It is well known that the plates easily delaminate by low velocity impact such as tool drop and fatigue loading. Therefore, there are many studies to evaluate the delamination resistance. In those, stick-slip phenomena has been reported in mode I delamination resistance measurements. In this study, the stick-slip phenomena was examined in detail with CF/Epoxy unidirectional lamia by changing loading speed of mode I delamination tests. Additionally, crack configurations were observed by using a scanning acoustic microscope during testing. The observation made it clear that nonlinearity between load and displacement relations reveals directly the beginning of the delamination crack propergation. Based on many experimental results, models of source of fiber bridging and delamination toughness were proposed and successfully verified by experiments.
