Prediction of Permeability in RTM Process for Composite Based on Multi-scale Approach

Abstract

Composite materials have high specific strength and specific stiffness. However, the application of composite materials has been limited for space and aerospace applications due to their relatively high price. Composite cost reductions due to mass production has greatly expanded their application to many industries, such as the automobile sector. The resin transfer molding (RTM) process can produce complex composite materials. Permeability in the RTM process refers to the resin fluidity, which can affect quality and production time because it determines the mold opening and closing times. It is normally measured using dedicated equipment. However, composite materials are anisotropic, and design changes cause material lay-up sequence, which impact on permeability, and lead to design delays by additional permeability measurement and increased design costs. This study proposes a virtual test method that predicts permeability using a multi-scale approach. Composite fiber permeability was derived from micro-scale fiber flow analysis using a commercial analysis tool. Meso-level woven models were selected to derive permeability within and outside tow. A simple theoretical expression of the woven model is presented and compared with analytical results, and a parametric study of the woven model pattern performed to identify the effect on permeability. As to undulation increases, fabric permeability decreases. Thus, permeability can be derived with a virtual test, significantly shortening the composite design process.