Compression after Impact Strengths of Stiffened Panels Made of CF/PEEK and CF/Epoxy.

摘要

Compression after impact (CAI) tests are conducted for stiffened panels made of carbon fiber (CF) /epoxy and CF/PEEK composite systems.Delaminations between skin and stiffeners are created by impact with various energy levels.Relationships between normalized impact energy levels with respect to thickness and delamination area are obtained through a robotic ultrasonic C-scan system.Compression tests are conducted with the aid of moire-topography camera and multi-channel acoustic emission analyzer.CAI strength of a CF/ PEEK panel is superior to those of CF/Epoxy panels.In the CF/PEEK panels, delamination propagation is well arrested just by the instance of catastrophic failure, and hence, high CAI strengths are obtained.In the CF/epoxy panels with a current skin of low axial stiffness, delamination propagation between skin and stiffeners is well arrested after initial separation onset.Hence, their CAI strengths are higher than those of thick plates where delaminations easily propagates transversely to loads.Initial buckling stresses are numerically obtained through a FEM code.Some factors are crucial for accurate predictions.Stress dependency of longitudinal elastic modulus of unidirectional CFRP is the most important point.For relatively short panels used here, delicate consideration of loading edge boundary conditions is required.Consideration of realistic initial imperfection slightly improves correlation between prediction and experiments.