OPTIMIZATION OF RESIN FLOW IN A FLEXIBLE MOULD INFUSION PROCESS FOR LARGE PRESSURE VESSELS

摘要

Permeability and fibre volume fraction of reinforcement fabrics are two parameters that are greatly influenced by the mould compression effect during the resin infusion process for the manufacturing of textile composite parts. In closed mould processes, such as resin transfer moulding (RTM), compression is determined by mould cavity, while in open mould processes such as vacuum assisted resin transfer moulding (VARTM) with flexible tooling on at least one side, the compression of the fabrics is mainly determined by the vacuum outflow pressure conditions. In our specific application of the production of a large pressure vessel, the mould setup consists of a fixed external mould and a flexible rubber tooling bag as the internal mould. The bag can be pressurized externally under controlled conditions in order to provide a compression force to the reinforcement fabrics before infusion. The effect of the enforced pressure conditions on the flexible tooling will be reflected on the fabric, as the generated compression effect will modify the permeability and fibre volume fraction. The object of this study is to optimize the pressure history and control of the inflatable bag during an infusion process for large textile composite pressure vessels in order to better control resin flow and minimize the effect of permeability and fibre volume fraction changes on process time and final part quality. Numerical simulation techniques of resin flow will assist in finding better process conditions such as flexible tooling pressure, infusion time, and final thickness of the part. Results of numerical simulations conducted show the importance of the thickness reduction phenomena in bag moulds and its influence on the real part. The inflatable bag used, considered as a rigid mould, gives improved results and manifests itself as best choice for the application. Simulations allowed reduced the need of expensive experimental prototype testing by means of virtual infusion process optimization.