Influencing Behavior Study of Natural Almond Shell Filler on the Tensile, Thermal, and Free Vibrational Properties of Flax Fiber Intertwined Vinyl Ester Composites

Abstract

The structural porosity weakness of a natural flax fiber-layered polymer laminate was reduced by the spatial rearrangement of natural almond shell filler occupying preferentially porous sites between the stacking layers, improving the properties of the polymer laminate. The present work investigates the mechanical, thermal, and free vibrational behavior of composites, including surface modification and the effect of almond shell filler loading in the flax fiber intertwined composites. Alkaline treatment of natural flax fiber and almond shell filler effectively reduced the hydrophilic contents of hemicellulose, lignin, and wax without altering the cellulose nature, as confirmed by FTIR analysis. Tensile strength was 35% higher for the alkaline-treated 10% almond shell-filled composite than the untreated filler composite. However, the tensile strength decreased beyond 10% of filler loading because of the poor dispersion of fillers in the matrix. As evident in the 10% filled almond shell composite, due to stronger interaction, polymer-mixed almond fillers act as a thermal insulating layer between the flax stacks, increasing thermal stability. Alkali treatment with an almond shell of 10 wt% filled flax fiber composite exhibited a higher natural frequency (185 Hz) and damping value (0.042) due to total internal dissipation of dynamic forces.

Keywords

• natural almond shell
• flax bast fiber
• chemical treatments
• vinyl ester composites
• thermal degradation
• damped frequency