Hybrid Epoxy Systems Modified with Abies alba Exudate: Cotton versus Silk Reinforcements

Abstract

The mechanical behavior of hybrid composite materials was studied based on a matrix composed of 50 wt.% Abies alba exudate and 50 wt.% epoxy resin, reinforced with cotton and silk fabrics. Composite plates were manufactured using a hand lay-up technique with a 40/60 resin-to-reinforcement ratio. Mechanical characterization included tensile, flexural, vibration, and Shore D hardness tests, supported by statistical analysis using one-way ANOVA and Bonferroni post hoc comparisons. The results showed that the introduction of textile reinforcement significantly improved all investigated properties compared to the unreinforced hybrid resin. Cotton-reinforced composites exhibited the highest tensile and flexural strength, as well as the highest hardness values, indicating increased stiffness and load-bearing capacity. In contrast, silk-reinforced composites demonstrated superior deformation capacity and higher damping behavior, reflecting enhanced ductility and energy dissipation. Statistical analysis confirmed a highly significant influence of material configuration on all properties (p < 0.05). An exception was observed in flexural deformation, where no significant difference was found between cotton- and silk-reinforced composites, suggesting a similar global deformation response. The results demonstrate that hybrid epoxy systems modified with Abies alba exudate can be successfully used for the development of bio-based composites.