A Computer Aided Design System for Three-Dimensional Compression Mold Heating

Abstract

Compression mold processing of composites involves taking the charge through a material dependent temperature and pressure path, inducing thermochemical reactions to cure the charge. While curing, specific uniform temperatures are required for a time, and spatial variation of the cavity surface temperature can lengthen time needed to cure and also cause voids and residual stresses, reducing the quality of the finished part. Towards mold heating design goal of uniform cavity surface temperature, an interactive CAD system for compression mold heating design has been developed. The system accepts a previously defined three dimensional, discretized goemetry and uses a Boundary Element Method (BEM) analysis which includes the effects of long, thin electric resistor heating rods, and is coupled with the CONMIN algorithm for constrained minimization of an objective error function to obtain uniform temperature over the cavity surface. Realistic constraints are featured to insure design feasibility. The problem is organized with design in mind to allow fast, easy redesign and a sensitivity study along with the optimization. The approach used is unique and is the first application of this type of optimization to three dimensional mold heating design. An example of the whole design process including creation, reviewing, optimization, and redesign of curved mold example is presented for results.