Flexible Injection is a newly proposed molding technique for fast manufacturing of fiber-reinforced thermoset composites. This new approach uses a deformable tool to speed up the injection process and apply a uniform consolidation pressure through the thickness of the composite during resin cure. Previous work showed that when dealing with complex geometries, the flexible nature of the tool could generate manufacturing defects such as resin rich zones and thickness gradients. The goal of the present study is to evaluate the impact of such imperfections on the distortion of a composite specimen after demolding. Firstly, a series of stair-shaped parts made of glass fiber and vinyl ester resin have been produced. By varying the processing conditions, it was possible to achieve very different lay-up qualities in the curved areas of the parts. A simple experimental procedure was then used to record the stability in shape of the parts as a function of temperature in order to extract the thermal reversible component of the deformation of the part. The experimentally measured spring-in is then compared with two types of modeling predictions: (1) classical analytical formula assuming perfect lay-up quality; (2) 2D parametric finite element simulations to account for the observed heterogeneities. Preliminary results indicate that the distortion is affected by manufacturing defects located in curved regions. This study highlights the importance of the preparation of the fibrous preform in order to ensure a successful implementation of Flexible Injection.
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