Studies on mechanical properties characterization of hybrid sisal and stinging nettle fiber reinforced epoxy composite material

This research investigates the mechanical properties of hybrid composite materials reinforced with sisal and stinging nettle fibers in an epoxy resin matrix. Sisal fibers, extracted from leaves, and stinging nettle fibers, obtained from stems, were chemically treated with a 2 % sodium hydroxide solution to enhance interfacial bonding and reduce moisture content. The densities of the treated fibers were measured using the pycnometer method. Composite specimens were fabricated using the hand layup method in accordance with ASTM standards, maintaining a constant epoxy resin content 60 % by weight. The remaining 40 % comprised a hybrid mix of sisal and stinging nettle fibers in five different weight ratios (10/30, 15/25, 20/20, 25/15, and 30/10) and were produced in both unidirectional and bidirectional fiber orientations. Notably, unidirectional composites exhibited the highest tensile strength, increasing from 50.67 MPa to 67.53 MPa as the sisal content rose from 10 % to 30 %. In contrast, bidirectional composites achieved higher flexural and impact strengths, with flextural strength increasing from 133.99 MPa to 162 MPa and impact strength from 6.8 J/cm2 to 10.07 J/cm2 across the same fiber ratio range. Compressive strength decreased with increased sisal content, dropping from 59.37 MPa to 51.65 MPa in unidirectional orientation and from 60.3 MPa to 53.9 MPa in bidirectional orientation. This study concludes that optimal mechanical performance of the hybrid composite can be achieved by strategically adjusting the sisal-to-stinging nettle fiber ratio and selecting the appropriate fiber orientation, depending on the specific structural or industrial applications.