Glass-fibre reinforced composite materials based on unsaturated polyester resins

The effect of glass-fibre content on the thermal and mechanical properties of cross-linked composites based on unsaturated polyester resins have been investigated by thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical thermal analysis and by measuring the heat distortion temperature (HDT). Two different matrix resins and two different glass mats were used, and the glass-fibre contents varied. Altogether 12 composite systems were tested. The glass- transition temperature of each composite was characteristic to the matrix resin and did not depend on the glass-fibre content, as it was expected. The effect of glass-fibre content on the storage modulus and on HDT has been elucidated. It has been found that up to 12 mass% (6 vol%) glass-fibre content the HDT did not change, above this value it increased with increasing glass-fibre content for each composite, but not at the same extent. This means that matrix-fibre interaction has an important role in the performance of the composites at elevated temperatures. Storage moduli increased with increasing glass-fibre content. The temperatures detected by dynamic mechanical thermal analysis corresponding to the storage modulus of 750 MPa—calculated by Takemori—are above the glass-transition and also increased with higher glass-fibre content in accordance with the real heat-distortion temperature measurements. It may be concluded that the effect of reinforcement on the performance of the composite could be detected more reliably by HDT measurements, since it gives information on the deformation of the composites. Matrix-fibre interaction has an essential role on the performance and on the HDT of the composite materials.