SIZING RELATED KINETIC AND FLOW CONSIDERATIONS IN THE RESIN INFUSION OF COMPOSITES

Fibres used in preforms of resin transfer moulded (RTM) composites are coated with sizings, binders, and/or finishes that serve multiple pur poses, including facilitating handling, protection of the fibres from compaction and process induced damage (including notching), aiding in compatibility and wetting of the fibres by the resin, and overall enha ncement of the behavioural response of the composites. In this investi gation four different sizings applied to S2 glass fibres are shown to significantly affect two aspects of RTM processing - resin infusion, a nd cure. In both cases phenomena at the microscopic level are seen to affect response variables at the macroscopic level. On a microscopic l evel, the behaviour of a thermosetting resin based composite is affect ed by the formation of interphase regions that greatly affect the cure kinetics and hence the mechanical and physical properties of the comp osite, which are dependent on the inter-constituent variations in loca l properties such as modulus and glass transition temperature. Similar ly fibre-sizing-resin interactions occurring during the infusion stage affect wet-out and local flow behaviour through the development of st oichiometric imbalances in local regions. It is shown that the molecul ar interactions between the constituents (as initiated by the sizing) are affected by processing conditions such as temperature and rate of resin flow, and that heat evolution and resin rheology may be affected by the stoichiometric imbalances resulting from interphasial level re actions.