Effect of fibre surface treatment on the mechanical response of ceramic fibre mat-reinforced interpenetrating vinylester/epoxy resins

A vinylester/epoxy (VE/EP ratio=1/1) hybrid resin of interpenetrating network (IPN) structure was reinforced by a needle punched ceramic fibre mat (30 wt%) composed of long discontinuous fibres (length ⩽50 mm). The surface chemistry of the ceramic fibres was varied by coating them with various organosilanes resulting in vinyl (VS) and epoxy (ES) functionalities. In addition, mats containing ceramic fibres without (initial sizing removed by burning, B) and with sizing by producer (as received, AR) were involved in this study. The mechanical response of the composites, produced by resin transfer moulding (RTM), was determined in tensile and flexural loading. The mechanical behaviour of the mat-reinforced composites strongly changed as a function of fibre surface treatment. Regarding to stiffness and strength the following ranking was deduced: VS ⩾ ES > B > AR. The failure mode of the composites was studied both in situ (using the acoustic emission technique) and post-mortem (fractographic inspection), and discussed.