Advanced mesomechanical modeling of triaxially braided composites for dynamic impact analysis with failure.

摘要

Numerical simulation plays an irreplaceable role in reducing time and cost for the development of aerospace and automotive structures, such as composite fan cases, car roof and body panels etc. However, a practical and computationally-efficient methodology for predicting the performance of large braided composite structures with the response and failure details of constituent level under both static and impact loading has yet to be developed.;This study focused on the development of efficient and sophisticated numerical analysis modeling techniques suitable for two-dimensional triaxially braided composite (TDTBC) materials and structures under high speed impact. A new finite element analysis (FEA) based mesomechanical modeling approach for TDTBC was developed independently and demonstrated both stand alone and in the combined multi-scale hybrid FEA as well. This new mesoscale modeling approach is capable of considering the detailed braiding geometry and architecture as well as the mechanical behavior of fiber tows, matrix, and the fiber tow interface, making it feasible to study the details of localized behavior and global response that happen in the complex constituents. Furthermore, it also accounts for the strain-rate effects on both elastic and inelastic behavior and the failure/damage mechanism in the matrix material, which had been long observed in experiments but were neglected for simplicity by researchers. It is capable of simulating inter-laminar and intra-laminar damage and delamination of braided composites subjected to dynamic loading. With high fidelity in both TDTBC architecture and mechanical properties, it is well suited to analyze high speed impact events with improved simulation capability in both accuracy and efficiency. Special attention was paid to the applicability of the method to relatively large scale components or structures. In addition, a novel hybrid multi-scale finite element analysis method, entitled Combined Multiscale Modeling (CMM) approach, has been developed in this comprehensive study in conjunction with dynamic submodeling technique. It was based on the newly developed mesoscale and existing macroscale approaches for modeling the braided composite materials. The CMM hybrid FEA approach enables the full use of the advantages of both the macroscale and the mesoscale approaches, with the mesoscale model or a more detailed macro-scale model to describe the details of local deformation and the macro-scale model or a coarser meso-scale model to capture the global overall response feature of the entire structure. The approach was verified with simple testing specimens and coupon plates, and may be extended to large systems like jet engine containment or automotive body panels. Without directly connecting different portions of the structure modeled with disparate approaches in the same analysis model, the submodeling technique maps the solution of a global model analysis performed for the full structure with less details onto the connecting interface on the portion of the same structure, the submodel, modeled with high fidelity and details. The CMM approach presented here captures the response feature of a triaxially braided composite structure under impact accurately with a much lower computational expense, making it feasible to analyze this type of analysis for exceedingly large structures.