Mixed-mode I/III fracture study of sandwich beams

The capacity of prestressed split-cantilever beam (SCB) for investigation of mixed-mode I/III fracture in foam core sandwich constructions was evaluated theoretically. The fracture was studied in terms of the strain energy release rate. In this relation, a three-dimensional finite-element model was developed. The strain energy release rate mode components were analyzed by the virtual crack closure technique. The analysis revealed that the mode I and the mode III components have maximum at the center of the crack front and gradually decrease toward the edges. Different mixed-mode ratios were generated by varying the mutual transverse displacement at the end of the sandwich SCB crack arms (in this way, the use of steel rollers with different diameters for prestressing the SCB to provide the mode-I part of the loading was modeled). The effect of the sandwich core material on the mixed-mode I/III fracture was investigated. For this purpose, three sandwich SCB configurations with different rigid cellular foams used for core material were simulated. It was found that the strain energy release rate decreases when the foam density increases. Therefore, the mixed-mode I/III fracture performance of the sandwich beams can be improved by using foams with higher density for core material.