An investigation of skin thickness and core material varietyon damage tolerance of carbon fiber reinforced sandwichcomposite structures

Sandwich composites are used in many different fields such as defense, construction, automotive, marine and aerospace, etc. where light weight is important due to their high ratio of strength and stiffness to weight. In addition to these important benefits, sandwich composites are extremely sensitive to impact. Low velocity impact damage is considered to be the most dangerous form of damage for these composites due to its imperceptibility. This study focuses on investigating the effects of different surface plate thickness and core types on the low speed impact performance of sandwich composites. Two different core materials were used: PVC Foam and PET Plate. PVC Foam is widely used as core material in sandwich composites. In this study, in addition to conventional core materials, PET Plate, which has a nominal density of approximately 28 times that of PVC Foam, was used as the core material. The top and bottom surface plates of the sandwich composites are made of woven carbon fiber/epoxy material. The 1 and 2 mm thick bottom and top surface plates have a crossply symmetric orientation. 4 different configurations of sandwich composites were produced. Cold press method was used in the production of sandwich composites. Low velocity impact tests were carried out with the weight reduction impact device in Başkent University Biomechanics and Strength laboratory. The results obtained from the tests and images of the post-impact damage of the sandwich structures and ultrasonic inspection results are presented comparatively. According to the test results, it is seen that the configurations (A-1 and A-2) using PET Plate as core material are the most resistant to impact load. The penetration depth values show that all specimens with B-1 and B-2 configurations were perforated. The core material nominal density value and the sandwich composite impact strength value are positively correlated, while the surface plate thickness has no significant effect on the impact strength compared to the core material nominal density.