Brittle Fracture in Key-hole Notched Polymer Specimens under Combined Compressive-shear Loading

In the present study, brittle fracture of the general-purpose Polystyrene (GPPS) is studied experimentally and theoretically under compressive-shear loading by using the Brazilian disk specimens containing a key-hole notch. The notched specimens are specified by different geometric parameters, i.e. the notch length and the tip radius. In this investigation, 84 fracture tests reported recently by the present authors are evaluated to assess the brittle fracture of key-hole notched specimens under compressive-shear loading. Two energy-based fracture models namely, the averaged strain energy density (ASED) and averaged strain energy density based on the equivalent factor concept (ASED-EFC) are proposed to predict the fracture loads of the tested GPPS specimens. The experimental and theoretical results are plotted for each case in the form of the fracture load versus the notch tip radius. Moreover, the analyses based on the finite element method as well as the experimental observations showed that although brittle failure in the test samples under compressive-shear loading takes place from the applied load side of the notch border by local tensile stresses, the notch bisector line and the other side of the notch border sustain compressive stresses. In fact this phenomenon states the concept of compressive-shear loading. Finally, it is shown that a good agreement exists between the experimental fracture load results and the theoretical predictions evaluated by using the two strain energy-based criteria.