Face Damage Growth of Sandwich Composites under Compressive Loading: Experiments, Analytical and Finite Element Modeling

Sandwich panels with composite laminate skins having [(+/- 45(C))(2),(0(C),0(G))(4),(+/- 45(C))(2)] stacking sequence (subscript C for carbon fibers, G for glass) and containing barely visible impact damage (BVID) induced on the whole sandwich structure impacted at low energy, were tested in edge after-impact-compression with load direction parallel and transversal to the fibers direction (0-dir.). The morphology of impact damage on the sandwich structure was determined by using ultrasonic C-Scan and visual observation of laminate cross section. A Digital Image Correlation (DIC) system was used to measure the delamination evolution during the test. Two different failure behaviors were observed in two different impacted panels. Panel with fibers oriented transversally to the compressive load showed an opening (Mode-I) propagation of a delamination, while the panel with fibers parallel to the load showed shear (Mode-II) propagation. The static load such to determine local buckling of the composite face and failure was experimentally measured. An analytical model was implemented to predict the static strength of laminate with Mode-I opening. An FE model was instead built to predict the local buckling failure mode of the laminate with BVID, which is the first phenomenon to appear. The results of the analytical model and the numerical simulation correlate well with the test.

Automated summary

Sandwich panels with composite laminate skins were tested for impact damage induced at low energy, with different failure behaviors observed in panels oriented transversally and parallel to the compressive load. Physical and visual analysis, as well as numerical simulations, were utilized to predict the local buckling failure mode and static strength of the laminate structures. The results of the tests correlated well with the analytical and numerical models.