Evaluation of mechanical behaviour of unidirectional fibre-reinforced composites considering the void morphology

Voids are one of the most common defects in fibre-reinforced composite materials. Insightful understandings of the correlation between void morphology and material properties can benefit the desired performance of industrial products. A two-level analysis method for unidirectional fibre-reinforced composites containing voids is developed based on micromechanical modelling. Representative volume cells at different levels are developed based on the description of fibre distribution and void geometry. Finite element analysis was performed on the representative volume cell to determine the effective elastic moduli. Good agreements are found among the finite element analysis results, theoretical results of Halpin-Tsai equation and experimental characterization from literature. Results show that the mechanical properties of composites are significantly affected by void morphology. Larger width-height aspect ratio leads to a less modulus reduction of in-plane modulus, but it produces larger reduction of out-of-plane modulus. Moreover, the finite element analysis results can give good explanation to the discreteness of the experimental characterization. It indicates that typical voids that are formed in the autoclave process have significant impact on the out-of-plane modulus. The study considered the temperature effect on the composite containing voids. Results show that there is no coupling effect between porosity and temperature.