Localized temperature rise as a novel indication in damage and failure behavior of biaxial non-crimp fabric reinforced polymer composite subjected to impulsive compression

Abstract

Non-crimp fabric reinforced polymer (NCFRP) composite is a suitable choice as structure material in aerospace use. One of the most important issues related to adiabatic failure is the correlation among temperature elevation, adiabatic shear band and failures of the material. In this study, impulsive damage and failure modes with temperature rise in biaxial NCFRP composite specimens were investigated under increased strain rates from 200/s to 2500/s. Path and distribution of temperature rise were experimentally characterized when the composite was subjected to in-plane and out-plane impulsive compression. It is found that (i) localized temperature can rise above a hundred degrees Celsius, reaching or even exceeding the Tg of the resin matrix and polyester tricot in specimen, which causes stress concentration and subsequent failure in warp/weft fiber tows in localized positions. (ii) For the out-of-plane compression, the localized temperature rise indicates dispersed inter-layer shear deformation in the biaxial NCFRP composite by stress wave mismatch effect. With the increase of strain rate, intensive temperature rise is a good announcement for an adiabatic shear band quickly and thoroughly splitting the specimen. (iii) For the in-plane compression, slight impact loading triggers small debonding and cracking along warp/weft fiber tows or at the fiber-matrix interface by fiber tows microbuckling effect. With the increase of strain rate, the localized temperature rise reveals that single shear band is developed and further evolved into zigzag shear bands, while catastrophic delamination failure is the dominant mode at higher strain rate. Higher temperature values at kinking positions are caused by fiber tows buckling-fold effect. Thermal degradation effect imperils the polymeric matrix and tricot around the kinking positions where bridging cracking, obstructing the spread of adiabatic shear band, and leading to the pull-out/breakage/splitting damages of warp/weft fiber tows. (iv) This work indicates that high-speed thermographic technology is an important method for investigating the dynamic behavior of composite materials. Localized temperature rise is an effective indicator in complex correlation with the multiple physical interaction including the adiabatic shear band, matrix/tricot softening, fiber tows kinking, localized damages and failures.