Fracture of particle-modified epoxies: effect of test rate and temperature

Abstract

This study compares the effect on the fracture energy of epoxy from addition of different weight % of particles, at both quasi-static and high test rates (up to 1 m/s). Silica and core-shell rubber (CSR) particles, and the hybrid of both (from 0.5 weight % to the maximum concentration of 25.4 weight %) are used. Tapered double cantilever beam (TDCB) and single-edge notch bending (SENB) specimens were used for measurement of the fracture energy, Gc. The silica and CSR formulations were then compared with ceramic microsphere and PES formulations. The toughening mechanisms involved were con rmed by fracture surface images obtained from eld emission gun scanning electron microscopy (FEG- SEM). Most of the specimens from all formulations show debonding and void growth is also expected in silica due to the relatively high fracture energy found. As the CSRs were made up from small CSR particles, mostly localised deformations were found, with some debonding of small CSR particles. In ceramic microsphere and PES specimens, fracture energy improvement was small, and the amount of improvement was similar. PES modifed epoxy shows different structures at different wt% as they were dissolved before mixing with the epoxy. Some brittle particles tear o were found in low wt%, while some local phase inversions were found in high wt%. The main mechanisms in PES specimens were particle pull out, bridging and debonding. The experimental results were compared with simulation results using the nite el- ement analysis software `Abaqus' and analytical models. When compared to exper- imental results, analytical models predicted the modulus and fracture energy of each formulation according, predictions agreed with experimental results, while di erent pre- dictions were found from FE model.