Bending fatigue behavior of glass-carbon/epoxy hybrid composites

A hybrid glass–carbon fiber reinforced epoxy matrix composite, characterized by the presence of intraply biaxial glass–carbon laminae as well as biaxial glass laminae and biaxial carbon aminae, was considered for its bending fatigue behavior. Displacement-controlled bending fatigue tests with R ratio of 0.10 were conducted on standard specimens and damage in the composite was continuously monitored through the loss of bending moment during cycling. The specimens were subjected to different fatigue loading, with the maximum load level up to 85% of the material ultimate flexural strength. Early damage was observed after a few hundred loading cycles causing degradation of material stiffness with cycling. The amount of stiffness reduction was observed to be a function of the magnitude of applied fatigue loading on the specimen. After 1 million cycles the fatigue test was stopped and residual properties were measured on tested specimens. Reduction in material strength and elastic modulus was found to depend on the level of fatigue loading. However, the reduction in stiffness did not exactly correlate with the reduction in strength. At last, possible use of the obtained data for the design of structural components is briefly addressed.