Characterization of Mechanical and Damping Properties of Nettle and Glass Fiber Reinforced Hybrid Composites

Growing environmental concerns are becoming significant challenges for large-scale applications in the automotive industry. Replacing and hybridizing glass fibers with natural fibers for non-structural applications is one effective way to address this challenge, while retaining the useful properties of both. This paper investigates the mechanical and damping performance of four types of compression-molded materials: polyester matrix (reference), nettle (6% by weight), hybrid 1 (6% glass and 6% nettle by weight), and hybrid 2 (12% glass and 6% nettle by weight), with polyester matrix at an ambient temperature. The tensile tests using digital image correlation (DIC) showed that by adding 6% by weight nettle fibers for polymer matrix tensile modulus increases by 21%. For the hybrid 1 two-layer composite (6% by weight glass and 6% by weight nettle) and the hybrid 2 three-layer composite (12% by weight glass and 6% by weight nettle), it increases by 80% and 101%, respectively. On the other hand, dynamic mechanical analysis (DMA) has been used to assess the damping properties of the materials. The results showed that the loss factor increased by 6 similar to 14% for nettle reinforced composite, by 8 similar to 25% for hybrid 1 glass-nettle reinforced composite and by 2 similar to 15% for hybrid 2 glass-nettle reinforced composite for frequencies around 1.0 similar to 2.0 Hz and around 12 Hz corresponding to vehicle body and suspension natural frequencies, respectively. These results showed that glass fibers can be replaced by nettle fibers without compromising performance.