Characterization of Mode I fracture mechanics properties of extruded polystyrene via double cantilever beam test using a side-grooved sample

Double cantilever beam (DCB) test is mathematically well defined and can provide a Mode I strain energy release rate based on energy considerations. Additionally, it enables consecutive measurements of the Mode I fracture mechanics properties during crack growth. Despite these advantages, it is difficult to find any examples performing the DCB test on extruded polystyrene (XPS), and knowledge on the fracture mechanics properties of XPS is quite restricted. In this study, DCB test is conducted using an XPS sample with side grooves on width/length or thickness/length planes, and the Mode I fracture mechanics properties are characterized during crack growth. In addition to the DCB test, four-point single-edge-notched bending (4SENB) tests were performed, and the results were compared with those obtained from the DCB tests. In the DCB test, the cracks grew unstably and stopped growing after a certain length in both the samples. In the sample with grooves on the width/length planes, the cracks propagated toward the end of the sample. However, in the sample with grooves on the thickness/length planes, the bending failure is induced before the crack propagated considerably. The Mode I fracture mechanics properties obtained using the samples with grooves on the thickness/length planes are two to three times greater than those obtained using the samples with on the width/length planes, and the increase in Mode I energy release rate during crack growth is more significant. Additionally, the statistical analysis suggests that there was no significant difference between the results obtained from the DCB and 4SENB tests.