Abstract: In order to analyze the directional influences on failure mode and mechanical behavior of diaphragm reinforced foam core sandwich beams caused by bulkhead′s arrangement direction, three point bending tests were conducted on 3 sandwich beams, which were made through vacuum infusion process including unidirectional reinforcement and bidirectional enhancements. The results show that the failure modes of sandwich beams reinforced by transversal, longitudinal and bidirectional bulkhead were top panel′s bending broken, lateral panel′s local buckling and top panel′s local shearing failure, respectively. The ductility of beams under lateral load was improved due to the reasons that inclined cracks propagation was prevented by transversal bulkhead. Compared with the unreinforced sandwich, the capacity and elastics modulus of sandwich beams strengthened by longitudinal bulkheads were increased by 1.02 and 5.65 times, respectively, while the ductility changes into 1.23 multiples of the original. Mechanical behaviors of specimens that were reinforced by longitudinal and bidirectional bulkhead are similar, and their carrying capacity and elastic modulus were superior to those reinforced by transversal bulkheads.

Key words: composites reinforced foam core sandwich beams, reinforced bulkhead, shear mechanical performance, failure modes, ductility