Bending behavior of multi-layer sandwich composites reinforced with weft-knitted spacer fabrics

In this study, the bending properties of multi-layer sandwich composites (MLSCs) were investigated. For this purpose, first, 1 × 1- and 5 × 5-Rib gaiting weft-knitted spacer fabrics were produced using E-glass yarns. Then, glass/epoxy sandwich composites were prepared using produced fabrics as reinforcement and epoxy resin as matrix. Considering both the pattern of reinforcements and the arrangement of layers, different types of MLSCs were fabricated by the implementation of different stacking sequences. The prepared samples were subjected to the three-point bending test. Generally, the orientation of samples, structures of each sandwich’s layer, and stacking sequence of layers, as three impressive parameters affected the bending behavior of MLSCs. The results showed that in all samples, the maximum bending force (MBF) of MLSCs in the longitudinal direction is generally higher than that in the transverse direction. The MBF of MLSCs included both 5 × 5-Rib gaiting layers and 1 × 1-Rib gaiting layers increased with increasing the number of 5 × 5-Rib gaiting layers to 1 × 1-Rib gaiting layers. The MBF of MLSCs included of same number of 5 × 5-Rib gaiting and 1 × 1-Rib gaiting structures increases by placing the 5 × 5-Rib gaiting fabrics in the bottom layers, which shows the influence of stacking sequence on the bending behavior of MLSCs. According to the generated geometrical models, two-layer MLSCs are numerically simulated using the FEM. FE simulation and the experimental results brought about the same bending behavior of MLSCs.