The critical buckling loads for various core densities and materials of honeycomb composite panels are experimentally and numerically investigated in this study. The surface plates of honeycomb composite panels are of polyester/glass fiber composite. Polyester resin-impregnated paper or aluminum is used as the honeycomb core material. Honeycomb panels with different cell sizes, but approximately the same volume, are produced and the effect of the honeycomb core density on the critical buckling load is investigated by compression tests. The critical buckling load of paper core panels is determined to be higher than that of aluminum core panels. It is seen that the buckling strength of the specimens increases by the increase of core density. As the critical buckling load exceeds a certain limit, regional core cell buckling and core crushing are seen in aluminum core panels. In paper core panels, regional cracks are seen, in addition to these failures. The study also calculates the numeric buckling loads of the panels using the ANSYS finite element analysis program. The achieved experimental and numerical results are compared with each other and the results are provided in tables.

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In this study, it was achieved failure analysis of wet-patch-repaired composite plates, experimentally. U notched composite plates were repaired with wet patch and then static tensile load was applied to composite plates. The patch thickness, single and double patch repair and fiber orientation angle of composite plates effect on the failure load were investigated. The composite plates having eight plies woven glass fiber and epoxy matrix resin, woven glass fiber and epoxy based adhesive were used as materials. The wet patches were obtained by epoxy adhesive impregnated to the woven glass fibers. As a result of experimental study, it was determined that the failure load was increased with increasing patch thickness. Also, it was seen that the double patch was more effective repair technique than single patch and the fiber orientation angle increasing was decreased the failure load of the composite plates.

This study presents experimental and numerical failure analyses for two serial pin loaded holes in unidirectional carbon fiber/epoxy resin composite laminates. The failure loads and failure modes of composite laminates are determined for different geometrical parameters and different stacking sequences. Three-dimensional ANSYS Parametric Design Language codes are developed in the ANSYS R finite element software. Hashin Failure Criteria and material degradation rules are used to determine failure loads and failure modes in the numerical analysis. Experimental and numerical results show that failure loads and failure modes were affected with geometrical parameters.