The thermal behaviour of glass fibre investigated by thermomechanical analysis

A TMA procedure has been developed with the capability of probing the thermal behaviour of glass fibre. A single glass fibre was successfully mounted into TMA fibre configuration and several thermomechanical programmes were carried out over a wide temperature range from 20°C to 900°C. It was found that measured coefficient of linear thermal expansion (CLTE) of boron-free E-glass fibre remained constant below 300°C and the values had an excellent agreement with that found in the literature. At higher temperatures an abrupt length change in glass transition region allowed for the determination of glass transition temperature (Tg). The results from isothermal measurement showed significant fibre length shrinkage, which was a function of both temperature and time. It follows that there exist two mechanisms, thermal expansion and structural relaxation, which together account for overall thermomechanical responses of glass fibre. The former is related to the decrease of Young’s modulus at elevated temperatures and the latter is considered responsible for the observed increase of room temperature Young’s modulus after thermally conditioning glass fibre at various temperatures.