Abstract: Composite foam sandwich structures are subject to delamination defects within their panels during manufacture and use, which can seriously affect the load-bearing properties of the structure. In this paper, the bearing performance of carbon fiber/polyurethane foam sandwich structures containing initial delamination defects within the panel under bending load is investigated using a combination of three-point bending test and finite element simulation, and the effects of the length and width of the initial delamination defects, as well as the location of delamination defect thicknesses, on the bending performance of the composite foam sandwich structures are analyzed. Based on the cohesive zone model (CZM), the extension evolution of initial delamination defects were analyzed, and the extension mechanism of initial delamination defects under bending load was discussed. The results show that the ultimate load decreases with the increase of the defect length and width, where the width has a greater influence; the expansion path of delamination defects is less affected by the size and shape, and the delamination defects expand transversely along the panel from the middle boundary of the defects; the location of the delamination defects is moved from the surface layer to the middle layer, and the ultimate load of the sandwich structure is then increased.

Key words: foam sandwich structure, finite element model, initial delamination defect, ultimate load, delamination expansion, composites