包覆纤维复合材料轴向压缩应力传递机理及破坏模式研究

Axial compression performance is one of the main factors considered in structural design of fiber reinforced composites.However, the properties of the fiber in the composites are weak because of the orientation structure in the composites. Filament fibers were covered with reinforced fibre bundles to improve the axial compressive properties of composites in this project, the effect of fiber covering on the axial compressive properties and failure modes of composites will be studied, quantitative relationship between fiber coating conditions and compressive modulus and failure strength of composites was established. Through observation of failure interface and internal microstructures, establishing the relationship between mechanical behavior and microstructural changes, than clarifying the transformation conditions between the two failure mechanisms of fiber buckling instability and kinking band failure. By in situ compression testing and microscopic observation,revealing the deformation and stress transfer mechanism of buckling reinforced and coated fibers, based on the characteristics of stress-strain field, the evolution law of compressive failure of coated fiber composites is further deduced. Through the establishment of material compression meso-structure model, the theoretical analysis of different conditions of fiber coated influence on the results of compression properties of materials, and experimental verification of theoretical model. The research results can further optimize the structure of fiber reinforced plastic, improve the efficiency of composite structure system, and promote the development of lightweight composite materials, which has important theoretical and practical significance.

轴向压缩性能是纤维增强复合材料在结构设计中考虑的主要因素之一，纤维在复合材料中的取向排列结构导致该性能较弱。本项目采用长丝纤维包覆增强纤维束的方法以提高复合材料的轴向压缩性能，研究纤维包覆对复合材料的轴向压缩性能和破坏模式的影响，建立纤维包覆条件与复合材料压缩模量、破坏强度的定量关系；观察材料破坏界面及内部微结构，建立力学行为与微结构变化之间的关联，阐明纤维屈曲失稳和扭折失效两种破坏机理之间的转化条件；通过原位压缩测试和微观观测，揭示屈曲变形增强纤维和包覆纤维的变形和应力传递机制，根据其应力应变场特征进一步推导包覆纤维复合材料压缩破坏的演化规律；通过建立材料压缩细观结构模型，理论分析不同条件纤维包覆对材料压缩性能的测试结果的影响，并实验验证理论模型。本项目研究成果可进一步优化纤维增强复合材料结构，提高复合材料结构系统的作用效率，推动复合材料轻量化的发展，具有重要的理论及现实意义。

本项目借鉴大自然中的缠绕仿生结构，依据纺织品设计中的包覆纱原理和复合材料的压缩屈曲失稳断裂机理，设计制备了具有高轴向压缩性能的包覆纤维增强复合材料。通过排列形式不同的多根纤维增强环氧树脂基复合材料并进行原位轴向压缩的观测实验，分析了纤维模量、排列角度及包覆等因素对纤维形变传递和损伤演化和断裂模式的影响；研究了包缠纤维种类、直径和包缠方式对包覆碳纤维复合材料的轴向压缩强度、模量的影响，分析包缠纤维直径大小对碳纤维束在压缩过程中对树脂界面结合性能、断裂模式的影响规律；基于有限元分析方法，基于有限元分析软件模拟渐进损伤演化过程，理解屈曲变形增强纤维和包缠纤维的应力传递机制和应力重新分布等问题。研究成果可为纤维复合材料压缩破坏机理调控提供科学依据和技术支撑。