The effects of glass-fiber sizings on the strength and energy absorption of the fiber/matrix interphase under high loading rates

The interphases of various sized E-glass-fiber/epoxy-amine systems were tes ted at displacement rates in the range 230-2450 mum/s by a new experimental technique (dynamic micro-debonding technique), By this method, the rate-de pendent interphase properties, apparent shear strength and absorbed energie s due to debonding and frictional sliding, were quantified. The systems inc lude unsized, epoxy-amine compatible, and epoxy-amine incompatible glass fi bers. The high displacement rates that induce high-strain-rate interphase l oading were obtained by using the rapid expansion capability of piezoelectr ic actuators (PZT). The results of dynamic micro-debonding experiments show ed that the values of interphase strength and specific absorbed energies va ried in a manner that is dependent on the sizing and exhibited significant sensitivity to loading rates, The unsized fibers exhibit greater frictional sliding energies that could provide better ballistic resistance, while the compatible sized fibers show higher strength values that improve the struc tural integrity of the polymeric composites. In addition, significantly hig her amounts of energy are absorbed within the frictional sliding regime com pared to debonding. By using the experimental data obtained, a case study w as performed to reveal the importance of the interphase related micro damag e modes on energy absorption (and therefore ballistic performance) of glass /epoxy composite armor. (C) 2001 Elsevier Science Ltd. All rights reserved.