Adhesively bonded joints of hybrid flax/jute fibre reinforced composites: An experimental study

This study examines how fabric architecture and hybridization affect the performance of adhesively bonded jute/flax composite joints. Single-lap joints were fabricated using epoxy-bonded composites, including neat jute, neat unidirectional (UD) flax, neat twill flax, and hybrid configurations with a jute core and flax outer layers, and then tested under tensile loading. The results show that fabric architecture significantly influences failure modes. Unidirectional flax fabric promoted controlled failure at the adhesive interface, while twill architectures tended toward delamination. Hybridization with flax substantially enhanced joint performance compared to neat jute. Hybrid joints with UD flax achieved up to 98% of the strength of neat UD flax joints, while twill flax hybrids reached up to 99% of neat twill counterparts. The UD architecture proved superior, showing up to 32% greater strength than equivalent twill flax hybrids. A key finding was that increasing from two to three flax layers provided a marginal strength improvement (<6%), demonstrating that fibre architecture dominates over the number of layers. SEM analysis showed that UD flax hybrids failed mainly by light fibre-tear (LFT), while twill flax hybrids exhibited severe delamination. These results demonstrate that optimal hybridization, particularly with just two UD flax layers, can deliver nearly the full bonded joint performance of neat flax composites while improving material efficiency and lowering cost. The study provides practical design parameters for the development of high-performance, sustainable natural fibre composite joints.