Simulation of Moisture Desorption from Carbon Fiber Reinforced Plastics with Protective Coatings after Long-Term Climatic Aging

The kinetics of drying at 60°C have been studied for a carbon fiber reinforced plastic (CFRP) based on KMKU-2 m.120 adhesive prepreg with a VE-46 fluoroepoxy coating and an AC-1115 acrylic coatings having different colors. The kinetics was registered after 8 and 13 years of exposure on an open testing bench under the conditions of a moderately warm climate. Differences in a relative change in the weight of different-size samples have been found and approximated with the use of Fick’s and Langmuir models in a one-dimensional and a three-dimensional approximation. The variants of the one-dimensional or three-dimensional Langmuir model turned out to be more preferable, since they take into account the transformation probabilities for bound water into mobile water and provide a much better convergence of the models under consideration. Anisotropy in moisture transfer has been revealed. The diffusion coefficient in the transverse direction exhibit a value being from 10 to 30 times smaller than it is in in the case of the reinforcement plane. It is revealed and proven that moisture transfer parameters inherent in carbon fiber reinforced plastic depend on the coating color, with remaining overall high climatic CFRP stability.