Test analysis on the flexural performances of repaired honeycomb sandwich structures

The flexural behavior of the repaired honeycomb sandwich structures, which were made up of carbon fiber reinforced polymer (CFRP) skins and honeycomb material, was investigated by four-point bending test. The bending performance of the repaired plate was analyzed under the influence of scarf ratio, flush repair method, damage size, repair equipment and repair material.The test results show that, the failure modes of all the repaired plate can be divided into three kinds: breaking at the edge of the patch, breaking at the middle of the patch and breaking at the adhesive film surface. The failure strength of the specimens with the same failure mode is close. The bending strength of the repaired plate of which the first two failure modes plate is similar to the undamaged plate, while the bending strength of the repaired plate of the third failure mode is relatively low. The strength recovery of all the repaired plate is basically higher than 95%. The analysis on the relative stiffness of sandwich structures shows that the stiffness of the repaired structures is close to the undamaged plate, which is consistent with the composite repair criterion.