Experimental determination of residual flexural strength and critical buckling load of impact-damaged glass/epoxy laminates

The main objective of this research is to find experimentally the effect of impact damage on the flexural strength of glass fiber/epoxy laminated composite materials at two different test conditions. The other objective is to determine the critical buckling load of laminated composite material after impact loading. Thus, the loss of flexural and buckling performances of the damaged material has been established by comparison with the undamaged material. Initially, angle-ply laminated composite plates with rectangular shaped have been subjected to impact load at different energy levels by using a drop-weight testing machine and impact damage has been created. To find the residual flexural strength, four-point bending tests have been carried out. Four-point bending specimens have been cut from the damaged area of the middle of the laminated plates and have been positioned in two different ways according to the face subjected to the impact. For buckling tests, a unidirectional compression load has been applied to the impacted specimens with the size of 100 mm x150 mm. According to the four-point bending test results, the flexural strengths of the specimens subjected to impact at 10 J and 30 J have decreased approximately 25 and 42%, respectively. Similarly, the reductions in critical buckling loads of specimens subjected to impact at 10 J and 40 J are approximately 16 and 32%, respectively. Consequently, the impact load significantly reduces the flexural and buckling performances of laminated glass/epoxy composites. Furthermore, the positioning of the four-point bending test specimen affects the flexural strength.