Stress Analysis of a Stepped-Lap Bonded Repair Joint in Composite Laminate under Compressive Loading

With increasing the usage of advanced composite materials in aircraft structures, it is required to have a suitable repair technology for composite airframe. One of the primary requisites of the repair in such structures is that the repaired surface should not affect the aerodynamic contour. Adhesively bonded repair joints are generally preferred over mechanically fastened repair joints to avoid the stress concentration and achieve smooth aerodynamic surface. Significant numbers of research works have been carried on interface stress distributions for lap, butt and scarf adhesive repaired joints under the static tensile loading. However, the behavior of stepped-lap adhesive joints under compressive loading has not been fully understood and there are not many literatures available on this subject. The present work focuses on stress analysis of a laminate that is repaired through a stepped-lap joint repair scheme. The stress analysis has been carried out and stress distributions in the laminate, patch and adhesive were studied. In order to establish and validate the FE approach for analysis of stepped-lap repair joint subjected to compression, an experimental study also has been carried out. The strains from the analysis have been compared with the strains obtained from the test at important locations. Both the results have shown good agreement