Fatigue and fracture behavior of adhesively-bonded composite structural joints

Constant amplitude fatigue loading spectra stand for only a small percentage of the real loading of a structure, although they can be used to investigate the fatigue and fracture behavior of structural elements. The fatigue and fracture behavior of adhesively-bonded structural joints under different constant amplitude loading patterns has been experimentally investigated and the results are presented in this chapter. Double-lap joints composed of pultruded glass-fiber-reinforced polymer-matrix laminates bonded by an epoxy adhesive were examined. The dominant failure modes are described and the stiffness degradation trends under tensile or compressive fatigue loads are presented. The results show a significant effect of the loading pattern on the lifetime and fracture behavior of the joints examined.