Shear Fatigue Degradation and Fracture of Random Short-Fiber SMC Composite

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Abstract
Cyclic degradation and fracture of a random short-fiber SMC composite subjected to shear fatigue was studied. Experiments were conducted on double V-notched Iosipescu SMC-R50 specimens under completely reverse cyclic shear loading. Owing to the random microstructure of the SMC-R50 composite, homogeneous fatigue damage was treated in a continuum sense. The cyclic shear stress-strain behavior was studied first. Macroscopic shear stiffness degradation and the rate of damage evolution during the shear fatigue were investigated also. Cyclic shear stiffness reduction up to 25 per cent of its initial value was common in most cases studied. A power-law relationship among the rate of damage, the cyclic shear stress amplitude, and the fatigue loading history was determined. The shear-fatigue fracture, resulted from nonhomogeneous growth of fatigue damage, was well-behaved, and a cyclic shear stress-life diagram was constructed for the SMC-R50 material.