A novel integrated model for 3D braided composites considering stochastic characteristics

• Theoretical derivation for the stiffness of 3D braided composites. • Integrated model of 3D braided composites considering multiple stochastic characteristics. • Dispersion transfer from micro-scale to macro-scale. • Experimental data validation and parameter effect investigation. Stochastic characteristics as random fiber arrangement, probabilistic distribution of fiber modulus, and voids are the critical nature of 3D braided composites, which possess a significant effect on mechanical performance. This work assumes the voids and fibers of the 3D braided composite components as spherical voids and cylinder inclusions, and build a dispersion transfer relationship between the micro-scale stochastic characteristics and the macro-scale mechanical behavior. The theoretical stiffness of 3D braided composites is derived using a dilute concentration method firstly, and then a 3D braided representative volume element (RVE) is established. It is found that the nonlinear behavior of 3D braided composites is resulted from the dispersion of fiber modulus. The higher the dispersion the earlier the nonlinear behavior occurs. When the yarn volume fraction is 50%, 2% voids result in a 5.5% decrease in the modulus of RVE in the z -direction and a 10.3% decrease in strength. While for the Weibull shape parameter β increasing from 10 to 90, the corresponding RVE strength decreases by 13.7%, but the modulus is broadly constant. As one would expect, this work finally provides an advance approach for predicting the mechanical behavior of 3D braided composites.