Forced-interaction and spring-in – relevant initiators of process-induced distortions in composite manufacturing

Abstract

Process-induced distortions are still an issue for today’s CFRP applications. Nonetheless, cost-reduction is considerably pushed by OEMs. Low cost tools, made from aluminum or steel, offer significant cost-saving potential compared to the state-of-the-art Invar (Ni36) tools. However, their high thermal expansion affects the final part shape detrimentally. The present paper reports on an experimental pilot study on forced-interaction and spring-in. Distortions of C- and L-profile specimens with unidirectional, cross-ply and quasi-isotropic laminates and thicknesses up to 8.2 mm were manufactured on Invar and aluminum tools. Local and global part distortions were evaluated after manufacturing and compared. The study gives new insight into both acting distortion mechanisms. It quantifies the effect of a high tool CTE on the final part shape, which is of great value for tool and part designers who strive for high-precision composites.