Resin Infusion under Flexible Tooling

Resin infusion under flexible tooling (RIFT) can be considered to be a variant of resin transfer moulding (RTM) in which one stiff mould face is replaced by a flexible film. It is seen as an alternative to conventional hand lay-up techniques as it offers many benefits, particularly with regards to health and safety whilst not involving the high tooling costs of a change to RTM. It is a vacuum driven process and as such fibre compaction may occur during vacuum bag preparation, prior to resin infusion and during resin infusion. The aim of the work was to examine the effect of the application of cycled loads equivalent to one atmosphere (i.e. the maximum load in a vacuum infusion process) on fibre beds to determine whether higher fibre volume fractions could be obtained. Mechanical compression testing has been conducted on both wet and dry fibre beds. Tests were conducted on two fabric types; a plain weave and biaxial stitched fabric of similar areal weights (weight per unit area). Results show that fibre bed thickness decreases with increasing number of cycles and is lowest for the wet fibre beds when compared to dry fibre beds. Fibre volume fractions for multicycle loading were also found to be higher when compared to equivalent fibre beds subjected to a long monotonic load cycle. Tests were also conducted to measure the dynamic fibre beds thickness during the RIFT process in an attempt to correlate the flow data with the mechanical compression work. Results indicate that the final laminate thickness may be predictable to an accuracy equivalent to one layer of reinforcement for the configuration tested. Knowledge of final laminate thickness is useful for the prediction of accurate mechanical properties and may lead to increased use of infusion processes in commercial sectors where they might not otherwise be considered. As part of this work a comprehensive literature review has been undertaken. Whilst the relevance of some papers may not be directly obvious, it is the case that aspects of other techniques and in particular fibre behaviour and resin flow are directly relevant or can be modified to suit RIFT like processes