Abstract
Modern engineering increasingly demands materials that offer both thermal and mechanical
stability under varying conditions, while also meeting sustainability goals. Although synthetic
fibres perform well, their negative environmental impact often compromises long-term
sustainability. To mitigate this, researchers are turning to natural, renewable alternatives that
are more environmentally friendly and recyclable. Bio-based materials are gaining attention in
engineering applications due to their availability, low environmental carbon footprint and
recyclability. Among these, the Borassus flabellifer (Palmyra palm) fruit husk remains an
underutilized biofibre in Bangladesh. Currently, it is primarily used for disposal or waste-to
energy purposes, despite its strong potential for high-value applications in sustainable
composite materials.
This study explores the potential of B. flabellifer husk fibre as a sustainable reinforcement for
high-performance bio-composites, aiming to enhance its current value by incorporating into
engineering applications. In the initial phase, both untreated and alkali-treated fibres were
experimentally analysed for their physical, chemical, thermal and mechanical properties using
standardized methods. The untreated fibre showed low density (0.74 g/cm³), low moisture
absorption, good thermal insulation and mechanical strength, making it a feasible candidate for
lightweight structural applications. Alkali treatment using 5% NaOH enhanced fibre
morphology by removing hemicellulose and surface impurities, thereby improving both
thermal stability and morphological property. Thermogravimetric analysis (TGA) showed that
treated fibres achieved high char residue (up to 32%) and integral process decomposition
temperatures exceeding 1000°C, confirming excellent thermal resistance, while FTIR and SEM
analyses verified chemical and structural improvements due to treatment.
In the final phase, composites were fabricated through hand layup using 10 wt.% fibre and two
epoxy types: conventional laminating epoxy, EL2 and high heat-resistant laminating epoxy,
EL160. The composites were evaluated for physical, thermal, thermo-mechanical,
morphological and outgassing characteristics adhering standards. While fibre inclusion had
minimal impact on density, it significantly reduced moisture and water absorption in treated
samples compared to untreated one. TGA results showed increased char content and
decomposition temperatures in all composites, with 2TBHFE and 0.75TBFHE performing
best. Dynamic mechanical analysis (DMA) revealed higher storage and loss moduli and
remarkable glass transition temperatures (Tg) and damping factors (tan δ), particularly in
0.5TBHFE and 0.75TBFHE, indicating improved energy dissipation and fibre-matrix
adhesion. Outgassing tests confirmed that alkali treatment significantly lowered total mass loss
(Mtml), meeting space material standards. SEM imaging further confirmed strong interfacial
bonding, with fibre breakage dominant in treated samples, in contrast to fibre pull-out in
untreated composites.
B. flabellifer husk fibre–reinforced composites, particularly those treated with NaOH for 0.5
and 0.75 hours, demonstrate improved performance comparable to conventional natural-fibre
composites. These materials offer a lightweight structural solution with enhanced thermal
stability, mechanical strength, and vibration resistance. As a result, they present a promising
and sustainable option for aerospace and automotive applications, supporting global net-zero
emissions targets for 2050 and aligning with broader sustainability objectives set by the
UNSDGs and the Paris Agreement, while also benefiting local communities in Bangladesh.