Cure Cycle Optimization for the Reduction of Processing-Induced Residual Stresses in Composite Materials

The control and reduction of processing-induced residual stresses has been investigated by modifying processing conditions for a graphite/BMI composite material. The effects of dwell temperature, dwell time, cool-down rate, cool-down pressure, and postcure on residual stresses were investigated using unsymmetric cross-ply laminates. The effects on transverse mechanical properties were also measured. Experimental results have shown that residual stresses can be reduced by as much as 25-30% while retaining or enhancing transverse mechanical properties by curing at lower temperatures for longer times or utilizing an intermediate low-temperature dwell in three-step cure cycles. Overall process cycle times are not lengthened for three-step curing.