Damage and damping of short-glass-fibre-reinforced PBT composites under dynamic conditions: Effect of matrix behaviour

The effect of a thermoplastic polyester elastomer (TPEE) on the damping properties and energy dissipation of PBT (polybutylene terephthalate) reinforced with short glass fibres is investigated in this study. Dynamic mechanical analysis (DMA) showed that tan δ increased significantly as a result of the incorporation of TPEE, especially for frequencies below 60 Hz. With increasing frequency, the storage modulus increased and the loss moduli decreased, with the loss modulus being higher for the TPEE composite. Tensile cyclic loading tests showed that more energy was dissipated during the first loading/unloading cycle for PBT TPEE composites than for PBT ones. Damage, characterized by degradation of the elastic modulus during sequential loading-unloading cycles, was analysed at strain-rates of 0.1, 0.2, 0.8 and 3.2 s−1. These experiments confirmed the DMA results and demonstrated that the TPEE composite dissipated more energy than the comparable PBT samples. SEM analysis showed that the incorporation of TPEE weakened the fibre-matrix interfacial bonding, especially in the ductile zones of the fracture surface. Moreover, localized deformation in the interface zone between glass fibres and the matrix was affected by the visco-damage behaviour, explaining the increase in the tan δ value for the TPEE composite.