Dynamic mechanical analysis and high strain-rate energy absorption characteristics of vertically aligned carbon nanotube (VACNT) reinforced woven fiber-glass composites

In previous research (Blast and Impact Dynamics Lab, University of Mississippi), it was found that Vertically Aligned Carbon Nanotube (VACNT) forests grown on Silicon (Si) wafer substrate exhibited significantly higher flexural stiffness, damping and specific energy absorption. In the work reported here, the dynamic mechanical behavior and energy absorption characteristics of nano-enhanced functionally graded composites consisting of 3 layers of VACNT forests grown on woven fiber-glass and embedded within 10 layers of woven fiber-glass; with polyester (FG/PE/VACNT) and polyurethane (FG/PU/VACNT) resin systems, are investigated. Dynamic Mechanical Analysis (DMA) was conducted for evaluating the dynamic mechanical behavior, and compressive Split Hopkinson Pressure Bar (SHPB) tests were performed to characterize the energy absorption.;Initially, 10 layer woven fiber-glass with polyester (FG/PE), polyurethane (FG/PU), and epoxy (FG/Epoxy) based resin systems were characterized; to find suitable candidate materials for embedding with VACNT forest layers. Among these, FG/PE and FG/PU, showing comparatively lower damping and higher compressive strength, were chosen for embedding with 3 layers of VACNT grown on woven fiber-glass with polyester (FG/PE/VACNT) and polyurethane (FG/PU/VACNT) resins. The dynamic mechanical behavior of VACNT forest reinforced composites, FG/PE/VACNT and FG/PU/VACNT, were compared with the baseline composites, FG/PE and PF/PU.;A Dynamic Mechanical Analyzer was used for obtaining the mechanical properties such as storage modulus (E', flexural stiffness), loss modulus (E'', energy dissipation), damping loss factor (Tan delta, inherent damping), and glass transition temperature (Tg). It was found that FG/PE/VACNT exhibited a significantly lower flexural stiffness at ambient temperature along with higher damping loss factor over the investigated temperature range, compared to the baseline material FG/PE. For FG/PU/VACNT, a significant increase in flexural stiffness at ambient temperature along with a lower damping loss factor was observed with respect to the baseline material, FG/PU.;A Split Hopkinson Pressure Bar was used to obtain the specific energy absorption and compressive strength under high strain-rate loading. It was found that the specific energy absorption increased with VACNT layers embedded in both FG/PE and FG/PU. The compressive strength also increased by about 30% with the addition of VACNT forest layers in FG/PU; however, it did not show an improvement for FG/PE.