Improved mechanical properties in laminated epoxy composites reinforced with high-content cellulose microfibrils from banana pseudostems

The development of high-performance structural hybrid polymeric biocomposites using agricultural waste as reinforcement is driving progress toward a more sustainable industry. In this study, cellulose microfibrils (CMFs) were extracted from banana pseudostem residues using a rapid and eco-friendly microwave-assisted method. The extracted CMFs exhibited a high crystallinity index (92 %), thermal stability above 349 °C, and diameters ranging from 7 to 13 μm.

These CMFs were incorporated at 60 wt% into laminated epoxy composites using a vacuum-assisted resin transfer molding (VARTM) process. Diglycidyl ether of bisphenol A (BADGE), a commercially available epoxy resin, was used as the matrix. Unlike conventional systems that rely on commercial woven fiber mats, the non-woven CMFs were successfully integrated without agglomeration or structural defects. The resulting composites showed a 63 % increase in Young's modulus (from 893 to 1456 MPa) and a 57 % improvement in tensile strength (from 32.4 to 51.04 MPa) compared to neat epoxy resin. Dynamic mechanical analysis revealed increases in storage and loss moduli and a broadened tan δ peak, indicating enhanced energy dissipation over a wide temperature range. Differential scanning calorimetry confirmed the presence of a sharp exothermic transition associated with the glass transition temperature. SEM analysis revealed uniform dispersion of CMFs and strong interfacial adhesion with the matrix.

Despite the high CMF content, the composite retained the low density characteristic of epoxy systems and exhibited increased water retention due to the polar nature of the reinforcement. This strategy offers a technically and environmentally viable route for converting agricultural residues into lightweight structural composites. The developed materials align with circular economy and green chemistry principles and show strong potential for applications in the automotive, construction, marine, and technical manufacturing sectors.