Study on compressive properties of microwave cured composites

Abstract

A study on the compressive properties of microwave cured glass fibre/epoxy composite has been carried out and the results are compared with those of thermally cured (autoclave) composites. Fractographic analysis has also been carried out after compression tests were done. Two orientations [0/90] and [±45] glass fibre/epoxy prepregs were fabricated and were cured in an autoclave and in a commercial domestic microwave oven with operating frequency of 2450 MHz.

Compressive properties of the microwave cured [0/90] and [±45] composites were comparable to that of autoclave cured ones. Better compressive strengths were achieved for both orientations of the microwave cured specimens when the pressure applied was even and uniform for compaction of laminates and to remove volatiles, and sufficient cooling was given after curing process to prevent residual stresses.

Fractographic analysis was carried out to observe the failure modes of both the microwave and autoclave cured composites. Residual stresses were more likely to be present in the microwave cured composites due to the current curing technique and set up, resulting in higher occurrence of residual stress induced failure modes that were only found in the microwave cured specimens.

Microwave curing has proven to be significantly faster than thermal curing and the tremendous cut down in curing time can be translated into energy and cost saving. Further improvement in the pressure application method in the microwave curing process could ease the problem of large scattering of data due to non-uniform curing in the current project.