Influence of Alkali Treatment and Stacking Sequence on Mechanical, Physical, and Thermal Characteristics of Hemp and Palmyra-Reinforced Hybrid Composites

Natural fibers are available in low cost, easily renewable and they are rich in cellulose. As the natural fibers possess impurities over the surface, poor wettability and interfacial bonding are the main drawbacks encountered during fabrication process. In the current research work, hemp (H) and palmyra (P) fibers were treated with different sodium hydroxide (NaOH) concentrations (2%, 4%, 6%, and 8%) for 5 hrat room temperature. The influence of stacking sequence (HHPPHH, HPHPHP and PPHHPP) and surface modification and on physical, mechanical, and thermal properties of hemp and palmyra fiber-reinforced epoxy composites were investigated with a 30 wt.% of fiber loading. The attributes such as water absorption, density, tensile properties, flexural properties, impact energy, hardness, and thermal conductivity were examined. From the experimental results, the 6% NaOH-treated composites compared with untreated fiber composites disclosed an increase of 19.34% for tensile strength, 16.77% for flexural strength, and 12.35% for hardness with stacking sequence of PPHHPP. The experimental thermal conductivity results show that there is a significant decrease in values after NaOH treatment of hybrid composites. The surface morphology of the untreated, treated reinforcements, and fracture surface of the tensile-tested hybrid composite specimens were examined by scanning electronic microscope.