EFFECT OF ISOTHERMAL CURE TEMPERATURE AND ENVIRONMENTAL CONDITION ON THE SHORT BEAM SHEAR STRENGTH AND FAILURE MECHANISM OF A CARBON/EPOXY COMPOSITE

摘要

This paper presents the effect of isothermal cure temperature and environmental condition on Short Beam Shear (SBS) strength and failure mode for a commercial carbon fiber prepreg (977-2 UD). The prepreg panels were cured at a wide range of isothermal temperatures (from 149℃ to 182℃) for 180 min and cut into test coupons. Half of the test coupons were tested at room temperature. The other half were conditioned at 71℃ with 85% humidity for 30 days and then tested at 82℃ (hot/wet). The room temperature/dry SBS strength for the specimens cured at isothermal temperatures ranging from 160℃ to 182℃ showed no significant variations. However, the room temperature/dry SBS strength for the samples cured at 149℃ showed a significant drop compared to the other specimens. The hot/wet SBS strength for all specimens showed a decreasing trend by reducing the isothermal cure temperature. Nevertheless, the hot/wet SBS strength drop was more significant for the specimens cured at 149℃. Also, the SBS failure mode of each sample was investigated using an optical microscope. The results of both room temperature/dry and hot/wet tests indicated a change in the SBS failure mode for the specimens cured at 149℃. Glass transition temperature of the specimens cut from the laminates was also obtained using Modulated Differential Scanning Calorimetry (MDSC).