Low Velocity Impact Strength of CFRP Composites Incorporating Nanoclay

Abstract

Carbon fiber reinforced polymer (CFRP) composites are the most commonly used material for aerospace applications. Damage of CFRP composites due to low-velocity impact from hail or small cosmic particles on airplanes or aerospace structures have been reported as a critical issue in aerospace applications. Since CFRP off-axis and out-of-plane responses strongly depend on matrix properties, we hypothesize that altering the matrix properties of CFRP using nanomaterials might result in a significant improvement in the low-velocity impact strength of CFRP. In this work, we present the use of nanoclay as a natural material with good chemical modification responses and a relatively low cost. Two loadings of nanoclay by weight of epoxy resin were examined; 4.0 wt.% and 10.0 wt.%. CFRP composite plates were produced using the epoxy-clay nanocomposites. The CFRP plates were then subjected to impact energy of 9 and 18 J representing a typical range for lowvelocity impact. Time-history response of load, displacement and velocity were monitored and reported. Moreover, 3D computer models generated from x-ray computed tomography (CT) scans of the impacted CFRP were examined to quantify the level of damage in CFRP. Finally, microstructural characterization was also performed to understand the significance of nanoclay intercalation on the behavior of CFRP composites fabricated using the modified nanocomposite. It was concluded that low content of nanoclay (4.0 wt.%), representing exfoliated platelets, does not have a significant effect on the low-velocity impact strength of CFRP. However, a relatively high content of nanoclay (10.0 wt.%), representing intercalated nanoclay platelets, has a significant improvement of the low velocity impact strength of CFRP. However, it was observed that these enhancements at 10.0 wt.% are associated with embrittlement of CFRP composite under impact. It is demonstrated that quantifying low velocity impact damage in CFRP using CT-scans might be possible for relatively low damage levels.