Process distortions in prepreg manufacturing – An experimental study on CFRP L-profiles

Process distortions are still a challenge in composite manufacturing. In academia and in industry, considerable effort is invested to characterize the main drivers inducing manufacturing distortions. However, due to the variety of different manufacturing techniques, such as resin transfer molding (RTM), resin transfer infusion (RTI) or prepreg processing, universal conclusions are not available yet. This paper focuses on process distortions in prepreg manufacturing using autoclave techniques. A comprehensive experimental study is performed that focuses on essential parameters such as lay-up, part thickness, part radius and scattering of occurring distortions. About 200 L-profile specimens are fabricated on invar and aluminum tools in order to study the effect of the tool material on spring-in. All specimens of this study are made from 8552/AS4 prepreg material. Experimental findings are compared to results published in the literature, while the effect of flange warpage is discussed in detail. Scattering of measured distortions is evaluated, while at least three specimens of each configuration are fabricated.