Moisture and Pressure Effects on Void Formation in Prepreg Processed Composites

摘要

A new generation of prepregs formulated for out-of-autoclave, or vacuum bag only, processing was investigated for void formation as a function of resin moisture content. Uncured prepreg was conditioned in a temperature/humidity chamber at 70, 80 and 90% relative humidity and 35°C. Conditioned prepreg was laid up into 16-ply laminates and cured using vacuum bag only processing, as well as partial vacuum and traditional autoclave processing. Moisture content in the resin was quantified using Fischer titration. Cured laminates were subjected to image analysis to determine void content. Experimentally obtained values for void volume fraction were compared with analytical predictions from a diffusion-based void formation model. Void content increased substantially with increasing moisture content in vacuum bag only processed samples, and a strong pressure dependence was noted. Under autoclave cure conditions, void-free parts were produced even at high moisture levels. Findings are discussed in the context of the mechanisms of void formation in prepreg processed composites.