Influence of different core configurations on the skin core bonding of sandwich composites

In a sandwich structure, debonding of skin and core is a critical issue. To improve skin–core bonding, T and dovetail shaped grooves were made on both sides of foam core and with these grooved cores, sandwich composites were prepared by vacuum infusion process. Epoxy resin mixed with milled glass fibers was used as the matrix. Sandwich specimens were subjected to flexural, compressive, and tensile tests according to ASTM standards, and the results are compared with standard specimens with plain core. On observing the failed specimens under flexural test, it is evident that plain and T grooved specimens experienced both debonding and core shear failures. Failure modes like skin crushing, micro-buckling and significant core shear are observed in the specimens with plain and T grooved specimens during compression test. The highest mechanical properties were demonstrated by specimens with dovetail grooves among the three types of specimens considered in this investigation. Compared to plain specimen, dovetail specimens showed 40% increase in the flexural strength, 82% increase in the compressive strength and 136% increase in the flatwise tensile strength. SEM images of fractured specimens indicate the major failure modes such as core shear, debonding in the specimens subjected to flexural testing. Based on this study, it is suggested to use cores with dovetail grooves instead of plain cores to manufacture sandwich composites in order to achieve enhanced skin–core bonding leading to superior mechanical properties.