Effect of particle morphology on mechanical behaviour of highly particle-filled composites

The mechanical behaviour and failure mechanism of highly particle-filled polymer composites (HPFPCs) with different particle morphologies over a wide range of strain rates (0.0001 /s to 1000 /s) and temperatures (-40°C to 100°C) are investigated using the nonlinear finite element method. The relevant micro-mechanical constitutive laws have been developed to characterize the mechanical performances of HPFPCs. The effects of particle shape and particle volume fraction (PVF) on the crack path and mechanical behaviour (peak strength and effective modulus) of HPFPCs are illustrated. Compared with the actual and circular particle shaped structures, the polygonal particle shaped structure shows the most stable crack path and possesses the highest peak strength and the lowest effective stiffness in corresponding PVF. It indicates that the fracture resistance of the polygonal particle shaped structure is better than the particle structure with smooth particle surfaces, especially when dealing with high strain rate problems. A sequence of failure mechanisms of HPFPCs with different particle morphologies can be observed. At higher strain rates of 100 /s and 1000 /s and lower temperatures of -40°C and -20°C, besides the interfacial debonding as the main crack path, the fracture of the extended binder filaments and the flow of small particles with extended binder matrix can be observed. While, at lower strain rates of 0.0001 /s and 0.001 /s and higher temperatures of 80°C and 100°C, micro-cracks are more scattered through the model as the binder matrix becomes more ductile. Besides, the effective stiffness is more sensitive to the particle shape at higher strain rates, while the peak strength becomes more sensitive to the particle shape at lower strain rates.