Micromechanical modeling of water-induced interfacial failure of ramie fiber reinforced thermoplastic composites

This paper proposed a micromechanical model to describe water-induced interfacial failure of natural plant fiber reinforced composites. The model was built with the consideration of fiber swelling, thick-wall cylinder deformation and analysis of shear-lag effect. Debonding tests and scanning electron microscope tests of ramie fiber/polypropylene micro-composites conditioned in environments with different water content were done to verify the model. The results showed that in the environment with 65% relative humidity (RH), the water-induced interfacial shear stress was predicted to be 1.51 MPa, much lower than the interfacial shear strength (IFSS) of dry micro-composites (19.67 MPa) and the interface was not damaged. In liquid water, a water-induced interfacial shear stress of 20.02 MPa was predicted, larger than 19.67 MPa and the interfacial adhesion was damaged solely by water absorption. At 90% RH, however, the predicted water-induced interfacial shear stress was only 5.32 MPa but premature debonding already occurred, which could be due to the matrix creep creating radial debonding.