Bending Behavior of Sandwich Structures with Different Fiber Facing Types and Extremely Low-Density Foam Cores

Abstract

Sandwich structures offer innovative alternative solutions in many weight critical industrial fields due to their lightweight and very high flexural rigidity compared to conventional materials. A vast number of sandwich configurations can be produced considering different type of materials for face sheets and core as well as matrix. Although there are many sandwich structures available in the literature to obtain the desired mechanical and physical properties, the usage of very low-density core materials is very limited. In this study, carbon and glass fiber fabrics having woven plain and ±45 fiber orientations and industrial PVC foam core having extremely low density of 40 kg.m-3 and 48 kg.m-3 were used to manufacture the sandwich panels. The fabrications of eight different configurations were performed by hand lay-up followed by vacuum bagging method. According to ASTM C393/C393M Standard, the sandwiches were subjected to three-point bending (TPB) tests. After performing the TPB tests, the composite sandwich specimens were examined under a stereomicroscope to determine the failure modes. The primary failure modes under quasi-static bending loading are found to be top face sheet failures due to fiber and matrix cracks and delamination, and core shear failures due to core crushing just below the top facing and core fractures. In addition, the consistency of the test results were verified and the effects of parameters were investigated by using statistical variance (ANOVA) and regression analysis. The study provides valuable contribution to the literature for sandwich structures having extremely low-density foam core materials, and may contribute to the material universe by introducing strong, stiff and lightweight sandwich composites. It gives a comprehensive comparison by considering the effect of different fiber types, fabric fiber orientations and core densities.

Keywords: Sandwich structures, Three-point bending, Flexural properties, Failure modes, ANOVA