A Study on Low Velocity Impact Behavior and Compressive Residual Strength of Carbon/Epoxy Composite Laminates(Composite 4)

The damage which is caused by the low velocity impact in composite laminates is the form of the failure which occurrs frequently in application structures. As the results of impact loading in composite laminates, matrix cracking, delamination and eventually fiber breakage for higher impact energies can occur. Even though no visible impact damage is observed, damage can exist inside composite laminates. This damage can reduce considerably the strength and stiffness of the composite laminates. And it can influence the structure stability and can be the initiation point of structure failure. The objective of this study is to assess impact properties, to determine the inside damage of composite laminates by impact loading and to evaluate residual compressive strength after impact. For this purpose a series of impact and compression-after-impact tests are carried out on composite laminates made of carbon fiber reinforced epoxy resin matrix with lay up patterns of [(±45)(0/90)_2]s and [(±45)(0)_3(90)(0)_3(±45)]. UT-C scan is used to determine impact damage characteristics and CAI(Compression After Impact) tests are carried out to evaluate quantitatively the reduction of compressive strength by impact loading.