Fictitious crack modelling of polymethyl methacrylate porous material

Fracture tests were performed on a granular polymethyl methacrylate porous material used as a mould for white ware castings. Two types of sample geometry (single-edge notch beam and wedge opening load) and two types of environment (dry at room temperature and in water at 45 °C) were used and the force–displacement curves were measured. The fictitious crack model with a bilinear softening curve was used to fit the experimental data resulting in an excellent agreement for all types of test. From the values of the fracture energy it is concluded that the measurement of the fracture toughness cannot be performed through a maximum peak load experiment for the given sample size and geometry. A comparison of the fracture surfaces under both conditions is made and an explanation for the different types of morphology is proposed.