Predictive Model for Tensile Properties of Carbon Fiber-Reinforced Polymers at Various Moisture Contents

Abstract

A model to estimate the tensile properties of carbon fiber-reinforced polymers (CFRP) based on their moisture contents and molecular structures is formulated and studied. In the proposed model, water molecules absorbed by polymers are considered congregated near the sub-micro-cavities within the polymers. The absorbed water molecules form hydrogen bonds with the polymer molecules and cause the regions around the sub-micro-cavities to have a reduced elastic modulus. The additive group contributions for polymers are used to determine the contributions of hydrophobic and hydrophilic functional groups separately. This enables the effects of water molecules on the mechanical properties of polymers to be quantified and estimated. For CFRP laminae, an additional effect of moisture on the fiber-matrix interface is considered in the calculation of the transverse tensile strength. The tensile properties are calculated using the proposed model agreed well with the experimental values. It is expected that the time and materials required to obtain the mechanical properties of CFRP exposed to humid environments can be reduced with the help of this model.