Interfacial micromechanics analysis on the ultrahigh molecular weight polyethylene bridging fibers crossing cracks

The micro-Raman spectroscopy was used to investigate the micromechanics of the ultrahigh molecular weight polyethylene (UHMWPE) bridging fiber crossing crack. The crack-arrest of the bridging fiber and the stress distribution of the interface between the bridging fibers and epoxy were mainly discussed by the micro-tension test coupled with Raman scanning. The crack propagation speed and the stress distribution of the specimens in different positions were also analyzed, and the shear-lag model was proposed to fit the stress distribution of bridging fibers at different tensile. The results show that bridging fibers, by dispersing partial external stress, can effectively withstand the propagation of crack. When the tensile strain is lower than the maximum strain of the UHMWPE fiber, the maximum stress on the bridging fibers existing at the crack center position, is less than 2 GPa, but the stress in the matrix is up to 12 GPa, which indicate the stress transfer value of fiber/matrix interface is less than 100%. The stress transfer model of UHMWPE bridging fibers is proposed to be parabola shaped, and the stress distribution of UHMWPE fiber exists in three zones, namely the bonded zone, the debonded zone and the bridging zone.