Single- and double-shear bearing strength of mechanically fastened joints in carbon fiber composite (CFC) systems have been studied and the analysis of results presented. CFC laminates made from unidirectional prepreg tapes as well as bidirectional fabric prepregs were tested in as-received condition at room temperature and under hot/wet environmental conditions after hygrothermal aging. The influence of geometric parameters like the specimen width-to-hole diameter ratio (w/d) and the specimen thickness-to-hole diameter ratio (t/d), on the bearing strength has been investigated.

Bearing strength tests were performed with three different fastener bolt materials and, in all, over 300 specimens were tested. Bearing stresses were evaluated at ultimate failure, at 2% hole deformation, at onset of nonlinearity, and at first load drop; and 2% offset bearing strength has been selected for the purpose of comparison of data. The influence of lamina configuration, mode of loading, hole-tolerance, and fastener bolt material on bearing strength has been investigated. The degradation of bearing strength in hygrothermally aged CFC specimens under hot/wet environmental conditions has been found to be around 25 to 30%, compared to the room temperature values.