OPTIMISATION OF LIQUID MOULDING TECHNIQUES APPLIED TOTHE PRODUCTION OF COMPOSITE MATERIALS FOR AUTOMOTIVEAPPLICATIONS

摘要

Liquid moulding techniques, in which a thermosetting resin flows through fibrous dryreinforcements, are commonly used in composite material production. In particular, the presentstudy focuses on Resin Transfer Moulding (RTM) and Vacuum Assisted Resin TransferMoulding (VARTM) processing techniques.In the case of a RTM technique, a dry reinforcement is embedded in a mould cavity, whereafter athermosetting resin is forced to flow in the cavity and wets the reinforcement itself whilst pushingout the air. After the cure process, the components are extracted from the mould and can be usedwithout any additional refinement operations. The infusion pressures are quite low (69 ÷ 690 kPa)[1] and any kind of fibre and reinforcement configurations may be used. In VARTM, the infusionpressures are lower than in the RTM, thanks to the vacuum application that promotes the infusionstep and the air evacuation.In the last few years, the automotive and nautical industries have shown increasing interest inthese techniques for the production of light components, but they also need to satisfyrequirements of enhanced speed and automation for the aforesaid process. For this reason, severalresearch paths have been followed:? A search for both highly reactive resins and high performance, light and high permeabilityreinforcements.?The use of software instruments for correct modelling during the infusion stage.? A definition of industrial strategies for the improvement of product quality, reproducibilityand cost saving.In this study, models of the reinforcement permeability (based on the Carman-Kozeny equation),and of the infusion stages for the RTM and VARTM techniques applied to both glass– and flax–reinforced composite materials were developed. These models permitted the prediction ofinfusion times when the processing parameters (infusion and cavity pressure), mould geometryand temperature, resin characteristics and the reinforcements’ volume fraction have been defined.Obviously, the results obtained for simple geometries can be extended to components havingmore complex shapes and larger dimensions.