*3.2. PMMA Beam Specimen*

The PMMA beam geometry offers a benchmark evaluation based on the numerical and experimental work of [31]. The beams were made of polymethyl methacrylate (PMMA), which is a standard material option for crack path investigations as it is relatively homogeneous and exhibits brittle fracture behavior at room temperature. The specimen was under a cyclic point load and acted on the top mid-span position with a value of 4.448 kN. The properties of the materials were taken as modulus of elasticity, *E* = 205 GPa, yield stress *<sup>σ</sup>y* = 516 MPa, threshold stress intensity factor Δ*kth* = 80 MPa√mm, Δ*KIC* = 730 MPa√mm, Paris law coefficient, C = 1.2 × <sup>10</sup>−11, Paris law exponent m = 3, and Poisson's ratio ν = 0.3. The thickness of the specimen was 12.7 mm and there were two different configurations depending on the initial crack length (a) and its position (b), as shown in Table 2. The specimen's geometry and the initial adaptive dens mesh are shown in Figure 8.

**Table 2.** Configurations of the PMMA specimen.


**Figure 8.** Problem statement for the PMMA specimen (dimensions in mm) and initial adaptive dens mesh.
