Study on the damage mechanism of moisture intrusion to the FRP/RPUF interface of composite cross-arms when considering the influence of temperature

Abstract

Moisture is more likely to infiltrate the FRP/RPUF interface with relatively weak internal insulation of composite insulated cross-arms in humid and hot working environments, leading to interface degradation. However, the damage mechanism after water infiltration into the FRP/RPUF interface under temperature conditions remains unclear. This study conducted moisture infiltration experiments and explored the damage mechanism after moisture infiltration into the FRP/RPUF interface under the influence of temperature using molecular dynamics simulations. The moisture absorption process at the FRP/RPUF interface is divided into two stages: Fick or Langmuir moisture absorption and physical moisture absorption. During the Fick or Langmuir moisture absorption stages, increased temperature enhanced the diffusion coefficient of water molecules and accelerated the moisture absorption rate of the material. Simultaneously, the proportion of bound water to free water in the system decreased, increasing the free volume fraction within the material. As the equilibrium between bound and free water was reached, the system could accommodate more moisture, thereby increasing the saturation moisture absorption capacity of the interface material. During the physical moisture absorption stage, increased temperature accelerated the decomposition rate of the material, intensifying the degree of interface bonding failure. Simultaneously, the thermal motion of the water molecules became more vigorous, increasing the influx of moisture into the sample through interface cracks. Consequently, the moisture absorption capacity and rate of the sample increased.