Automation of autoclave cure of epoxy/graphite composites

Tests were conducted on cured 100 ply epoxy/graphite composite laminates. It was found that the temperature used differed by approximately 10% from the value the oven finally reached. This showed up mainly as an offset between the actual and transfer function plots as time increased. Estimation of midpoint temperature from a location near the laminate surface is important if system dynamics have to be determined quickly or if a thermocouple cannot be placed at the midpoint due to structural or aesthetic reasons. In this study, a simple isothermal boundary condition was used to develop this concept. The results of an experiment to demonstrate that the transfer function is independent of the magnitude of the imposed step change. A 25% step change was used in the determination of system dynamics. 50% was approximately the magnitude of step change that would raise the laminate to a final temperature of 180°C, the curing temperature of this material.