Crack Propagation Simulation and Experimental Validation in Fracture Toughness Tests of GIS Epoxy Insulators

Epoxy resin plays an indispensable role in the field of electrical insulation due to its exceptional mechanical and insulation properties. However, its high crosslinking density results in a brittle cured product with insufficient toughness and poor ability to suppress crack initiation and propagation, leading to frequent failures. Therefore, it is crucial to study the crack propagation law under operational conditions. Based on the fracture phase field theory, this article develops a phase field simulation model to evaluate the fracture toughness of epoxy resin and simulate its crack propagation behavior. To determine the parameters of the simulation model, the elastic modulus and Poisson’s ratio of various epoxy resin formulations were obtained through tensile tests. The single-edge notched bending (SENB) method was employed to precisely measure the fracture toughness of the epoxy resin, which was then used to calculate the phase field characteristic width. In addition, a 3-D optical profilometer was utilized to analyze the fracture roughness of fractured samples and the crack width of partially fractured samples, thereby verifying the physical meaning of the phase field characteristic width calculation equation from an experimental perspective. Finally, to address the issue that the classic damage degradation function cannot adequately simulate the brittle fracture of epoxy resin specimens, an improved logistic function is proposed to achieve the brittleness simulation of epoxy resin, demonstrating consistency with experimental results.