STRENGTH OF THE FIBER THERMOPLASTIC-MATRIX INTERFACE UNDER CYCLIC COOLING TO LOW-TEMPERATURES/

The effect of cyclic cooling from ambient temperature down to liquid n itrogen temperature on the shear adhesive strength tau of fiber/polyme r joints was investigated. The joints between thermoplastic poly(aryle ne sulphone) PSK1, poly(phenylene sulphide sulphone)) and thermosettin g (epoxy, modified epoxy, Rolivsan) matrices and high strength steel w ire were examined. It was demonstrated that the multiple cooling produ ces losses in adhesive strength. The level of losses depends on the na ture of joint components, on the cyclic numbers and on the size of joi nt. It was concluded that the decrease of boundary strength is mainly determined by thermal residual stresses. As a result of their action t he fiber/matrix interface can be almost totally destroyed. The adhesiv e strength in this case does nor depend on the area of joints and has a very small value. (C) 1997 Elsevier Science Limited.