Mechanical and bending creep behavior of long bamboo fiber/nano-alumina/epoxy ternary composites

Bamboo fiber (BF) reinforced composites are attractive for sustainable engineering, yet their performance is hindered by weak fiber-matrix adhesion, the brittleness of the epoxy, and pronounced creep under warm and humid conditions. This study reported the synergistic strengthening and toughening achieved by impregnating long bamboo fibers with a polydopamine (PDA) primer that immobilized 20 nm alumina (Al₂O₃) nanoparticles (3 wt%) prior to epoxy infusion. The engineered interphase raised flexural strength, modulus, and impact toughness to 161.92 MPa, 9897.73 MPa, and 26.35 kJ/m², gains of 23.5 %, 22.2 %, and 20.1 %, respectively; while the glass transition temperature rose from 58.1 ◦C to 67.3 ◦C. Short-term flexural-creep tests (120 min) conducted at three stress levels (25 %, 50 %, and 75 %), temperatures (25 ◦C, 50 ◦C, and 75 ◦C) and relative humidities (25 %, 50 %, and 75 %) revealed markedly improved creep resistance, as evidenced by lower deflection, higher creep modulus and extended endurance. Stress exerted the dominant influence, followed by temperature, and then humidity, whose combined action accelerated creep and fracture. A six-parameter viscoelastic model captured the creep response more accurately than the classical four-element model. These findings provide a quantitative basis for predicting service life and designing reliable bamboo-fiber composites in structural applications.