Evaluation of sandwich panels with composite tube-reinforced foam core under bending and flatwise compression

In some applications such as roofs and walls, it is important to supply low thermal conductivity and high bending stiffness to structures. Generally, foam materials are preferred, which have low thermal conductivity. However, bending stiffness and compression properties of foam materials are low. In this study, composite tubes were inserted to the foam core material to improve the compression and bending properties of the sandwich structure. Vacuum infusion method was used to manufacture the sandwich structure. The bending and compression performance of the structures with and without composite tubes were compared. To measure the bending stiffness and compression properties of the structure, three-point bending and compression tests were conducted according to American Society for Testing and Materials (ASTM) standards. The manufacturing procedure can be easily automated and applied to large and complex shape panels. In addition, a parametric analysis was done to investigate the effect of the number of tubes and the diameter of the tubes on bending and compression stiffness of the structure. According to the test results, the samples including the composite tubes gave six times higher bending stiffness as compared to the samples without the composite tubes. As the diameter of the tubes increased the bending stiffness and the ultimate core shear strength increased. In addition, the structures including 14 mm diameter tubes had higher specific absorbed energy values under compression loading.