Experimental investigation of thermo-viscoelastic degradation and microstructural evolution of CNT-modified bamboo fiber reinforced epoxy composites

Bamboo fiber reinforced epoxy composites have emerged as promising sustainable materials for lightweight structural applications; however, their performance under elevated temperatures is governed by the combined effects of thermal degradation, viscoelastic response, and microstructural evolution. This study investigates the thermo-viscoelastic degradation behavior of bamboo fiber/epoxy composites reinforced with varying carbon nanotube (CNT) contents using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile testing, and scanning electron microscopy (SEM). The incorporation of CNTs increased the degradation onset temperature from 278 °C to 292 °C and the residual char yield from 18% to 24%, indicating enhanced thermal stability. The glass transition temperature increased from 72 °C to 81 °C, while the storage modulus improved from 2.1 GPa to 2.8 GPa, demonstrating restricted polymer chain mobility and enhanced interfacial load transfer. The optimum composite containing 1 wt.% CNTs exhibited the highest tensile strength of 85 MPa, compared with 72 MPa for the unmodified composite. SEM observations confirmed improved interfacial bonding and a more compact fracture morphology at the optimum CNT content, whereas excessive CNT loading promoted agglomeration and defect formation. These findings establish the relationship between thermal stability, viscoelastic performance, mechanical behavior, and microstructural evolution, highlighting the importance of uniform CNT dispersion for improving the elevated-temperature performance of bamboo fiber reinforced epoxy composites.