Low velocity impact behaviors of sandwich composites with preloads

Nowadays, the importance of composite materials is increasing with the spread of aviation, defense and space industries. Carbon fiber reinforced composites, which are widely used in composites, have a low density, high impact resistance, high wear, fatigue resistance and vibration damping properties. Thermoset resins are widely used in the manufacturing of composite materials as a matrix structure due to their high thermal stability, hard structure and abrasion resistance properties. Because of these properties, carbon fibers and thermoset resins were chosen in the scope of this study. Vacuum assisted resin infusion method was used in the production of the specimens. Composites laminas were produced with carbon woven fibers in the stacking sequence of [0/90]6 and kevlar woven fibers stacking sequence of [0/90]4. Sandwich composites were produced in the stacking sequence of [(0/90)3/PET/[(0/90)3] carbon and stacking sequence of [(0/90)3/PET/[(0/90)3] kevlar. The curing process was carried out at 80 ° C for 12 hours. The specimens were then cut to dimensions of 150x150 mm. Low velocity impact tests were applied to specimens with compressive, tensile and shear preload of 250 µm and without preload. According to the results, the maximum deformation values of the composites under compressive preload increase with increasing the preload level.