Effect of temperature and strain rate on the strength of a PET/glass fibre composite

Abstract

Constant strain-rate mechanical testing and surface fractography were used to characterize the failure behaviour of a PET/glass injection-moulding compound and of its unfilled matrix material. Parameters for this investigation were temperature and strain rate. The matrix material exhibited a viscous-brittle transition between room temperature and 60° C. Low temperature failure occurred by craze growth, followed by slow and rapid crack propagation. The composite material likewise behaved as a viscous solid at superambient temperatures. Failure at low temperatures and/or high deformation rates occurred by brittle matrix fracture and fibre pull-out. Under these conditions, mechanical properties improved, relative to those at room temperatures. At intermediate temperatures and/or low strain rates, failure occurred via matrix crazing and crack propagation near the fibre ends. An observed serration of the fracture path at high strain rates is suggested to be due to the need for high shear stresses at the fibre-matrix interface.