Temperature dependent dynamic compressive response of PA66-GF30 composite under constant strain rate multiaixal loading

This paper studies the uniaxial and multiaxial dynamic compressive behaviour and failure of PA66-GF30 (30 wt % glass fibre reinforced polyamide 66), a typical light weight and high strength composite increasingly used in automobiles including the electric cars in applications from ambient temperature to elevated temperatures up to 90 °C. Likewise, the constitutive relation of PA66-GF30 is characterized from quasi-static to high strain rates. Constant high strain rate loading is achieved by pulse shaping technique on a bespoke split Hopkinson bar. The stress-strain relations are pressure, strain rate and temperature dependent. Effects of strain rate and temperature are found to be decoupled on the pressure sensitivity of PA66-GF30. Beyond maximum stress, micro crack has already formed in dynamically deformed PA66-GF30, which corresponds to macro strain localization monitored by high speed photography and digital image correlation techniques. The PA66-GF30 with confinement shows adiabatic shear failure, with fibres coated by severe shear matrix facets and evenly distributed filaments. This is different from the unconfined PA66-GF30 which shows fibres pull out in the fractured matrix. A modified Drucker-Prager model is proposed to describe the pressure dependent compressive strength of PA66-GF30 over various strain rates and temperatures.