A multi-scale finite element approach for the mechanical behavior analysis of 3D braided composite structures

With the development of composite processing technology, three-dimensional braided composites have been widely used in automotive, aerospace and other high-tech industries. Due to specific yarn distribution in microstructure, three-dimensional braided composites have excellent mechanical properties. To further optimize or design their mechanical performance, it is important to accurately estimate the effective mechanical properties of braided performs with different braiding parameters such as braiding angle, pitch length and fiber volume fraction. To this end, the microstructure (i.e. yarn pattern) of braided perform generated by 1 × 1 four-step braiding process was first analyzed in detail with the three cell model, which was established from the simulation of braiding process. Secondly, multiphase finite element method was employed and introduced into asymptotic expansion homogenization framework to predict the equivalent elastic modulus and microscopic stress of three-dimensional braided composites. Finally, the calculated equivalent engineering elastic modulus was proved to be in good agreement with experimental measurements of braided composite samples. Thanks to the multi-scale approach, the microscopic stress, i.e., local stress state of the composite perform under macroscopic load can be obtained simultaneously, which can be used in further study of damage and failure behavior.