High performance/high rate composite processing with trapped rubber

Paper in proceeding, 2019

Trapped rubber processing (TRP) is an autoclave alternative to achieving high pressures during polymer matrix composite processing, utilizing thermally induced volume change of a nearly incompressible material inside a closed cavity mould. Recent advances in material and computational technology have made this processing technique more attractive. Computer electronics research has led to the development of elastomers with relatively high thermal conductivity. In addition, recent advances in computer processing have opened the possibility to simulate complex thermomechanical processes with finite element analysis. In this study, the volumetric change and resulting pressure is captured via a series of experiments. These experiments are used to characterize the dynamic in situ change in temperature, the dynamic change in volume and the resulting real-time change in surface pressure at multiple locations throughout the sample. The material characterization includes an iterative testing and computational modelling framework where the design of experiments is fed by initial material models based on the linear coefficient of thermal expansion and then the characterization is improved by the experimental tests. The silicone rubber elastomer used in this initial study was chosen to be compatible with the cure cycle for Hexcel M21 epoxy prepreg system, due to the large amount of material and processing data available. The development of an accurate thermomechanical material model of nearly incompressible elastomeric polymers for use in advanced trapped rubber processing modelling will allow more design freedom with more advanced shapes and less risk of processing failure while maintaining the possibility for custom distributions of pressures and temperatures, therefore, high-quality consolidation during curing.