Numerical modeling of the erosion of alumina particulate reinforced epoxy-matrix composites: Material removal mechanisms including reinforcement fracture

Abstract

Sacrificial composite coating layers are used to protect surfaces from solid particle erosion due to the high-speed impact of particles. Epoxy-based coatings are easily reapplied and are sometimes mixed together with a reinforcing phase consisting of ceramic particles in an attempt to lower the erosion rate. Previous experiments have indicated that different erosion mechanisms can occur depending on, amongst other things, the relative sizes of the reinforcement and abrasive particles. In the present work, a coupled finite element/smoothed particle hydrodynamics (FE/SPH) decomposition method was used to model the erosion of an epoxy-matrix composite reinforced with relatively large 0.5 mm alumina (Al2O3) spheres, by irregularly shaped 152 μm silicon carbide (SiC) abrasives. 5600 overlapping impacts of SiC particles were modeled on carefully chosen representative volumes of the particulate reinforced composite. A Johnson–Holmquist material model (JH-2) with dynamic tensile strength was used to model the particulate phase, while the epoxy was modeled using a piecewise linear plasticity material model coupled with a Cowper-Symonds strain and strain rate hardening relationship. Realistic abrasive particle morphologies were modeled, based on measurements of the abrasive powder used in the verifying experiments. The erosion rates at both perpendicular and oblique incidence were successfully predicted to within ∼10% of those measured. Both the model and experiments showed that the erosion resistance of the composite was higher than the epoxy at oblique incidence; however, at perpendicular incidence, even though the erosion rate of the reinforcements (0.67 ± 0.04 mm3/g) was lower than that of the epoxy (1.27 ± 0.1 mm3/g), the erosion rate of the composite was slightly higher (∼1.38 ± 0.16 mm3/g) than that of the epoxy. It was shown that this occurred because, as the epoxy eroded in a typically ductile fashion with cutting and ploughing mechanisms, the reinforcements fractured leading to an approximately level eroded surface at any instant. The model was able to capture these material removal mechanisms which were also confirmed using non-contact profilometry of the eroded surfaces.