Model experiment on a protrusion method for measurement of interface shear sliding stress in fiber-reinforced composite

Interface debonding, sliding and protrusion behavior in tungsten fiber-reinforced epoxy matrix model composite under 'protrusion test' have been studied. Interface shear-sliding resistance of the composite is obtained from three routes: (i) applied stress-sliding length relation; (ii) applied maximum stress-protruded fiber length at loading; and (iii) applied maximum stress and protruded fiber length after unloading. The shear sliding stress is obtained applying a constant shear stress analysis. It is found that interface debonding proceeds spontaneously with the increase of applied stress from the surface at a soft metal side and one unit of debonding is about twice the fiber radius. The constant interface shear stress approach could explain applied stress-interface sliding length relation below a maximum critical applied stress. The shear sliding stresses obtained from the three routes agree and the agreement demonstrated possibility of obtaining the constant shear frictional stress using a protruded fiber length after complete unloading. However, care should be taken to eliminate Poisson's effect; i.e. a maximum applied stress exists for a given composite and experimental condition.