William Walbran

Simulation and experimental validation of force controlled compression resin transfer molding

The simulation of composite manufacturing processes is a great aid to obtaining efficient production and high-quality parts. The mold and process design must allow for fast filling times as well as dry-spot free parts. Besides an accurate simulation of the resin flow through the reinforcement, the compaction response of the preform is also needed. The stress response of the textile to compaction has an influence on the local and global forces exerted on tooling. The numerical prediction of the clamping force helps to trade-off fast production times against affordable machinery. This article describes the accurate simulation of force controlled Resin Transfer Molding (RTM) and Compression RTM, and compares results of simulations with experimental data. A parametric study is performed in order to minimize the simulation time without compromising the accuracy of the results. The controlled force algorithms have been implemented within SimLCM, a code under development at the University of Auckland to address the liquid composite molding (LCM) family of manufacturing processes. With these new tools, the trade-off between production process time and equipment cost can be considered, and optimal process design solutions found.

Evaluating the shear component of reinforcement compaction stress during liquid composite moulding processes

During the compression of fibrous preforms for complex part geometries, a shear component of the reinforcement compaction stress is present in addition to the normal component. Consideration of the shear stress is required when modelling the forces experienced by mould tools used for liquid composite moulding processes, as they contribute significantly to the total clamping force required during reinforcement compression for high draw angle geometries. The friction coefficient between glass-fibre reinforcements and various mould surfaces has been evaluated. Processing parameters, such as mould closing speed, fibre volume fraction and number of layers of reinforcement, have little influence on the magnitude of the friction coefficient. The presented results validate the use of a simple friction model within liquid composite moulding process simulations.