The strength of glass fibre reinforcement after exposure to elevated composite processing temperatures

The results of a study on the properties of glass fibres after thermal conditioning at typical engineering thermoplastic processing temperatures are presented. The mechanical performance of rovings and single fibres of well-defined silane sized and water sized E-glass fibre samples was investigated at room temperature after thermal conditioning at temperatures up to 400°C. Thermal conditioning for 15 minutes led to strength degradation of greater than 50% at higher temperatures. The tensile strength of silane coated fibres was relatively stable up to 300°C but exhibited a precipitous drop at higher conditioning temperatures. The water sized fibres exhibited an approximately linear decrease in strength with increasing conditioning temperature. The strength distribution of the water sized fibres could be well represented by a unimodal three parameter Weibull distribution. The strength distributions of the sized fibres were more complicated and required the use of a bimodal Weibull distribution. The results are discussed in terms of the changes in surface coating and bulk glass structure during heat conditioning.