The effect of model dimensionality on compression strength of fiber reinforced composites

Abstract

Strength of fiber reinforced polymers (FRPs) under compression loads is typically limited by a shear localization failure mode called microbuckling which is highly sensitive to fiber misalignment. In addition to the magnitude of fiber misalignment, the dimensionality of fiber misalignment also plays a prominent role in the prediction of compression strength. Therefore, a comparison between 1D, 2D, and 3D fiber misalignment is carried out in a finite element setting with a homogenized representation of fiber and matrix materials. In real FRP structures, fiber misalignment is spread in a correlated random manner throughout the material volume resulting in a distribution of compression strength. Spectral representation method is used for developing the volumetric representation of fiber misalignment in numerical models, thus preserving the spatial correlations of fiber misalignment. As an input to the spectral representation method, two different functional forms of spectral density of the fiber misalignment are considered. The results of model series based on functional forms of spectral density are also compared against a reference model series based on experimental measurements of the fiber misalignment. Finally, a simple relation is proposed for prediction of compression strength at different percentiles of distribution of failure strengths with regard to scaling of mean square spectral density.