The properties of glass fibres after conditioning at composite recycling temperatures

Results are presented on E-glass fibre properties after thermal conditioning up to 600 °C. Thermal conditioning led to up to 70% strength degradation. Tensile strength and failure strain of silane-coated fibres were relatively stable up to 250 °C but exhibited a precipitous drop at higher conditioning temperatures. Unsized fibres exhibited a linear decrease in strength with increasing conditioning temperature. Little significant strength regeneration was obtained from a range of acid and silane post-treatments of heat conditioned fibres. A simple analysis of the cumulative fibre strength probability resulted in more useful understanding than the Weibull method. The modulus of both fibre types increased linearly with conditioning temperature. Evidence was found of a slow time-dependent reduction of glass fibre modulus during storage in an uncontrolled environment. The results are discussed in terms of the changes in surface coating and bulk glass structure during heat conditioning and the role of the glass fibre water content.