In this paper, a volume criterion based on a simple scalar quantity, the mean value of the strain energy (SED), has been used to assess the static strength of notched components made of Polymethylmethacrylate (PMMA). The local-strain-energy based approach has been applied to a well-documented set of experimental data recently reported in the literature. Data refer to blunt U-notched cylindrical specimens of commercial PMMA subjected to static loads and characterised by a large variability of notch tip radius (from 0.67 mm to 2.20 mm). Critical loads obtained experimentally have been compared with the theoretical ones, estimated by keeping constant the mean value of the strain energy in a well-defined small size volume. In addition, some new tests dealing with V-notched specimens with end holes have been carried out to investigate the effect of the notch opening angle.

Extensive brittle fracture curves are presented in the present paper for engineering components weakened by a U-shaped notch under different in-plane loading conditions from pure mode I to pure mode II. The curves were obtained in a computational manner on the basis of an appropriate brittle fracture model, namely the U-notched maximum tangential stress (UMTS) criterion, suggested and employed several times in the past by the author and his co-researchers to assess mixed mode fracture in numerous U-notched samples. Eight different notch tip radii were considered in the computations. Extensive brittle materials were also taken into consideration by using different values of the material critical distance in the calculations. By estimating theoretically the load-carrying capacity and the fracture initiation angle using solely the two basic material properties, namely the ultimate tensile strength and the plane-strain fracture toughness, engineers can design conveniently the U-notched brittle components and structures aiming to avoid abrupt fracture.