Micro-bolt repair for delaminated composite plate under compression

Abstract

This study proposes a method for repairing delaminated composite plates using micro-bolts. We first conducted a test to examine the effect of the hole size on the tensile strength of composite laminates. The test results showed that, among laminates with the same total area of holes, those with multiple small holes had a higher tensile strength than those with only a single large hole. Based on this result, brass bolts with a 0.6 mm diameter were used to repair the delaminated composite plates. Buckling tests and analysis were conducted for an intact laminate without delamination, an unrepaired laminate with delamination, a repaired laminate using one bolt, three bolts with two types of layout, and nine bolts. The test results indicate that the unrepaired specimen demonstrates local buckling at 68% of the buckling load of an intact specimen. In contrast, the buckling load was recovered to 82% of that of an intact specimen when only a single brass bolt was fastened. When nine bolts were used, the buckling load recovery rate increased to 90%. Finite element analysis produced the same results as the test, and predicted that the use of nine steel bolts will increase the buckling load to 93%.