Multi-scale modeling of the anisotropic, nonlinear damage behavior of carbon fiber reinforced plastics

近年来，对由碳纤维增强塑料（CFRP）制成的结构部件的需求在几个工业分支中急剧上升。有两种重要的增强材料：单向增强材料，其中所有纤维平行排列，以及纺织增强材料，其中增强纤维是编织的。后者是有利的，因为可以在几个方向上优化机械性能。另一方面，与单向复合材料相比，纺织复合材料引入了额外的几何复杂性，导致了显著的局部应力和应变集中，是纺织复合材料非线性、损伤和失效的主要驱动因素。为了在层合结构设计中考虑这些影响，其层由CFRP和纺织增强材料组成，本项目采用了多层次多尺度方法。首先，将开发一个细观力学模型的丝束，其中的纤维和基体分别建模。接下来，介观力学模型上的纺织品规模制定inludes在一个均匀的方式和帐户的几何效应，由于丝束的曲率的微观尺度的影响。最后，建立了一个适用于真实的结构和构件的宏观力学模型。本项目的主要目标是建立一个材料模型，该模型可以预测单层内的损伤演化。为此，使用连续描述的渐进损伤。该模型应考虑整个复合材料的各向异性、基体材料的塑性以及不同方向上损伤组分之间的相互作用。此外，分层，这是层的界面未结合，是要考虑的，因为它构成了层合结构中的主要失效机制之一。这两个，层内以及层间（脱层）的损伤进展将反映通过使用统一的模型被开发。

In recent years, the demand for structural components made from carbon fiber reinforced plastics (CFRP) has severely risen in several branches of industry. There are two important categories of reinforcements: the unidirectional ones, where all fibers are aligned parallel, and the textile ones, in which the reinforcing fibers are woven. The latter are advantageous because the mechanical properties can be optimized in several directions. On the other hand, compared to their unidirectional counterparts, textile composites introduce additional geometric complexities, which cause significant local stress and strain concentrations, being primary drivers of nonlinearity, damage, and failure within textile composites.In order to account for these effects in the design of laminated structures, whose layers are composed of CFRP with textile reinforcement, a hierarchical multi-scale approach is applied in the current project. At first, a micromechanical model will be developed for the tows, in which the fibers and the matrix are modeled separately. Next, a mesomechanical model on the textile scale is formulated which inludes the effects of the micro-scale in a homogenized manner and which accounts for geometrical effects due to the curvature of the tows. Finally, a macromechanical model is set up, which is suitable for application to real structures and structural components.The main goal of this project is the development of a material model, which allows predicting the damage evolution within single layers. For this, a continuum description of progressive damage is used. This model shall consider the anisotropy of the entire composite, the plasticity of the matrix material, and the interaction between damage components in different directions. Moreover, delamination, which is the interfacial unbonding of layers, is to be considered since it constitutes one of the major failure mechanisms in laminated structures. Both, the intralaminar as well as the interlaminar (delamination) damage progression will be reflected by using the unified model to be developed.