Quasi-static failure behaviour of PMMA under combined shear-compression loading

Quasi-static shear-compression tests were conducted on polymethyl methacrylate (PMMA) polymer specimens using a universal materials testing machine to investigate their failure behaviour under quasi-static multi-axial loading. Instead of using confining pressure, cylindrical specimens with bevelled ends of different angles (5°, 10°, 15°, 20°, 25° and 30°) were used to generate different shear stresses. In addition, a cylindrical specimen with no bevelled ends and a hat specimen of PMMA were applied in the quasi-static shear-compression tests to determine the compression and shear strengths of PMMA, respectively. Experimental results show that the failure force of PMMA decreased as the tilt angle of the specimen increased. Furthermore, the failure locus of the material can be predicted using a macroscopic failure criterion with an elliptical shape. The deformation modes of each type of PMMA specimen under quasi-static loading were determined.