Developing a Progressive Damage and Failure Model for Hybrid 3D Woven Textile Composites using NCYL Multiscale Metho

Results from a research study concerned with developing an experimentally validated computational tool for predicting the progressive damage and failure response of 3D woven textile composites (3DWTCs) in a multiscale framework are presented. There are different constituents within the textile composite; fiber tows, including carbon, glass and kevlar. The dry fiber tows are infused with SC-15 polymer matrix into a single composite material. The 3DWTCs are made through a 3D textile weaving process. Three different versions of hybridized architectures are examined to determine the progression of failure under tensile and compressive loading. The different types of 3DWTCs are compared against one another to understand the benefits of hybridization and the resulting performance enhancements. The scope of the project also includes conducting a micro-CT analysis to study the effect of microstructure imperfections on predicting the progressive damage and failure response, using a two-scale computational mechanics framework. The micro-CT analysis delivers information on the size of a representative unit cell (RUC), the fiber tows cross sectional details and the porosity (if any) within the composite. These microstructure scale inputs are the building blocks for 3D geometric modeling and finite element (FE) analysis of unit cell (or a collection of these) at a global scale. The objective of this work is to perform a multiscale investigation to study the progressive damage and failure at different length scales. In the computational modeling, the macroscale finite element analysis (FEA) is carried out at the representative volume element (RVE) and coupon level, while the micromechanics analysis is implemented simultaneously at the subscale level using material properties of the constituents (fiber and matrix) as input. The subscale micromechanics analysis uses the N-layers concentric cylinder model (NCYL) to compute the local fields in the fiber and matrix cylinders. The influence of matrix microdamage at the subscale leads to progressive degradation of fiber tow stiness at the macroscale, modeled using a secant moduli approach, resulting in the pre-peak nonlinear response. The post-peak strain softening response resulting from different failure modes like fiber tow rupture, tow splitting and matrix cracking in fiber tow, as well as inside the volume of textile, are modeled using a mesh-objective smeared crack approach (SCA). The FE models, in addition to being generated using nominally perfect geometry, are also generated directly from Micro-CT data using the software tool SIMPLEWARE. The FE mesh generated using this tool is a replication of real in-situ imperfection in the structure. A study on modeling the geometric imperfections and its effect on global stress-strain response of the structure is carried out both at RVE and Coupon level as a part of this research. The use of analytical solutions at the fiber-matrix scale in a multiscale framework delivers a distinct computational advantage in the damage and failure analysis, where high fidelity and computational efficiency are both gained at the same time.