Control of stress relaxation and residual thermal stress during cure of random fibre mat-reinforced polyester composites

摘要

The study deals with the control of stress relaxation and residual thermal stress during cure of random fibre mat-reinforced thermoset composite through a practicable optimal temperature scheme to manufacture timely and quality composite laminates with good mechanical properties. Samples were cured at 85? for 3 hours and cooled down under 10 different cool-down paths designated, Modes I to X. It was found that the stepped cool-down mode with subsequent fanning, Mode IX, gave the highest strength of 86MPa at the end of cool-down, and showed only a change in stiffness from 1.8GPa to 2.9GPa. In contrast, the quenched samples strength of 63MPa was among the least but increased remarkably both in strength (99MPa) and stiffness (2.5GPa) at the end of 4 months. This suggested that Mode IX relaxed out the residual thermal stress induced as the composite cooled down while Mode I had the highest thermal stress of 36MPa which relaxed with time.