Effects of nanoscale inclusions on impact resistance of Kevlar-epoxy laminate composites
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Kevlar, an aramid fiber, is one of the most widely used materials for various industrial applications, such as aerospace, automotive, sports, wind energy, biomedical, optics, as well as defense due to its extraordinary mechanical and thermal (fire retardancy) properties and lightweight. In the present study, graphene nanoflakes and nanoclays dispersed in epoxy resins at different weight percentages (0 to 10 wt.%) were incorporated with dry Kevlar fibers through wet-layup process, and then cured under vacuum and high temperature to make Kevlar/epoxy hybrid composites. The prepared composite panels of 16-ply were impact tested using a low-velocity impactor, and C-Scanned before and after the impact tests. During the impact tests, the impact force vs. displacement, impact force vs. time and impact energy values of the composite panels were analyzed and compared. The c-scans of the damaged composite panels were analyzed for damage area and depth. The damaged test panels were exposed to UV light and moisture for 8 days, with an interval of 4 days. The water contact angles around the damaged area were measured for each damaged composite panel. The test results, impact analysis and damage analysis showed that the nanoscale inclusions in the Kevlar/epoxy composites had a major impact in dissipating the kinetic energy into heat, other forms of energy, and elastic and plastic deformation, and thus saving the composite panels from the major damages. This comparative research study illustrated that the variation in nanomaterials in the epoxy of a composite makes a significant difference in the impact response of the laminate. This result may be useful for the further improvement of the Kevlar-based products in various industries.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering