A crucial factor in a composite repair installation is the degree of surface preparation that is available. The surface profile that is created is directly proportional to the bond strength of the composite repair to the substrate. A NACE-2 near-white metal sandblast is ideal surface preparation for a composite repair. However, this degree of surface preparation is not available for every installation for various reasons. As a result, this paper details the effects of several different kinds of surface preparation on composite bond strength.
Details are presented for the lap shear testing of a carbon fiber reinforced polymer (CFRP) according to ASTM D5868. Five different surface preparation techniques are tested, including NACE-2 sandblast, bristle blast, wire brush, carbide grinder, and sand paper. The testing is used to calculate the necessary degree of surface preparation required to sustain an acceptable field repair.
Test samples are fabricated according to the ASTM standard, and are tensile tested on an MTI-5K tensile machine. The lap shear values are compared to acceptable values required in the ASME Post Construction Code 2. Industry experience is also considered as it is determined whether these surface preparation methods are acceptable for in-situ composite repair.