Fracture investigation of PMMA specimen using coherent gradient sensing (CGS) technology

In this paper, the principle of coherent gradient sensing (CGS) technology in the transmission mode is briefly introduced. Fracture experiments of the PMMA specimens with offset crack under three-point-bending are performed using the CGS optical method. A series of CGS fringe patterns around the crack tip is used to study the fracture characteristics of the cracked specimens, such as the evolution of the crack tip stresses, deformation field and crack initiation, etc. Based on the K-dominance condition, the stress intensity factors at the crack tip are extracted by means of the distribution of CGS fringes, which show good agreement compared with the results from finite element analysis. The influences of the offset distance on fracture characterization are discussed. These results will be useful for evaluating the strength and lifespan of PMMA materials and structures.