Process Induced Distortions of Composite Structures due to Through- Thickness Fibre Volume Fraction Gradients

Abstract

During the production of composite parts unavoidable deformations occur. In order to meet the strict tolerance requirements of industry branches such as the automotive industry it is essential to understand the underlying mechanisms of these deformations. While much research has been done on the anisotropy driven spring-in effect and also on warpage caused by part-tool interactions, there are only a few studies on deformations driven by a fibre volume fraction gradient (Vf-gradient) in the through-thickness direction of a laminate. Especially for large, thin-walled parts with complex geometries, this effect leads to additional unwanted deformations either locally in curved part areas or even on a global level throughout the entire part. A comprehensive experimental study has been performed examining the effect of a Vf-gradient on process induced deformations. L-shaped carbon fibre reinforced, fast curing epoxy resin based specimens are investigated. The occurring deflections are compared with the predictions of an analytical model. The results are relevant for the future development of robust prediction methods for process induced distortions of large, thin-walled composite parts.