Prediction method of compressive strength after impact for fiber reinforced plastic composite based on damage fractal dimension

The bearing capacity of fiber reinforced plastic (FRP) composite is highly sensitive to low-speed impact damage, making the prediction of compressive strength after impact crucial for their engineering applications. In this study, residual compressive strength tests were conducted on laminates of carbon fiber reinforced plastic (CFRP) 5284RTM/U3160 with three different layups under barely visual inspection damage (BVID). Prior to compression testing, the impact damage morphology of laminates with different layups was captured using C-scanning, and the impact damage morphology was studied based on fractal dimension. The research results indicate that specimens with higher damage fractal dimensions exhibit lower compressive strength after impact. Based on this, a prediction model for the compressive strength of composite materials after impact was proposed, which is based on the fractal dimension of the impact damage morphology. This method takes the impact damage morphology as an equivalent geometric component – Sierpinski carpet, and obtains the area of laminates no longer participating in load-bearing after damage through the damage fractal dimension, thereby obtaining the residual compressive strength of the laminates. The predicted results of the model match well with experimental results, and it does not require impact energy as an input parameter, making it convenient for engineering applications.