Empirical damage evaluation of graphite/epoxy laminate bolt joint in fatigue

Abstract The bearing and fatigue strength of a bolt joint in a (±45/O 2 /±45/O 2 /±45/O 2 /90)s graphite/epoxy laminate is analyzed. A damage parameter is defined in terms of the change in the elongation of the bolt hole after a predetermined number of cyclic loading. Experimental data are obtained for specimens tested under a dry and wet environment at room and elevated temperature. Damage accumulation is reflected by data on bolt hole elongation. Physical damage of the laminate is examined and showed that fiber bundle fracture started at the interior of the laminate and progressed to the exterior with increasing load. Damage around the bolt hole was noticeable by the congregation of microcracks in the matrix and hence it depended on the fiber orientation. Enhancement of interfacial debonding was also observed when specimens are fatigued in an elevated moisture/temperature environment.