3D编织复合材料整体加筋壁板结构稳定性研究

To reduce the weight of the aircraft structures, as a kind of the novel lightweight structures with the good integrity, the integrally stiffened 3D braided composites panels are looking forward to being widely applied to improve the damage tolerance and design allowables for the composites structures, which can overcome the weakness of the delamination of the laminated composites due to their low interlaminar toughness and strength. Investigation of the stability of the new type of integrally stiffened thin-walled structure has become one of the key problems to be urgently solved for assessing the carrying capacity and ensuring the safety of the structure. However, since 3D braided composites are manufactured with the braided preforms by Resin Transfer Molding process, which makes the braided composites with the complicated microstructures directly become the structure at the same time. The feature of the composites makes it difficult to conduct the design and analysis of 3D braided composites sturctures. Nowadays, there are still few literatures about the stability analysis of the integrally stiffened 3D braided composites panel. In the proposal, first, a new structural model about 3D braided composites panel is presented. Based on the model, 3D braded composites panel are assumed to be composed of the upper and lower surface unit cell layers and the interior unit cell layers, and the constitutive relationship of each unit cell layer can be believed to be uniform orthogonal anisotropic at the macro-scale. Then a two-scale scheme is proposed to correlate the mechanical behaviors of the unit cells at the meso-scale with the response of 3D braided composites panel at the macro-scale. Finally, by considering the geometric nonlinearity of the structure and the material nonlinearity due to the damage of the structure components, the nonlinear finite element models are established to study the critical buckling load and the buckling mode of the integrally stiffened 3D braided composites panels subjected to the axial compression load or the inplane shear load. The distribution rule of the structural internal forces and the load transfer mechanism of the structure will be clarified. The effect of the structural parameters and the process parameters on the nonlinear buckling behaviors of the structures subjected to these typical loads will be discussed in detail. The corresponding experiments of the integrally stiffened 3D braided composites panels will be conducted to disclose the whole buckling behaviors and validate the calculation models. The numerical results and the experiments data will provide an important basis for the optimization design and analysis of the integrally stiffened 3D braided composites panel.

3D编织复合材料整体加筋壁板作为一种新颖的轻质高效结构，具有良好的结构整体性，能克服传统层板易分层的弱点，有望提高结构损伤容限及设计许用值，以进一步减轻飞行器结构重量。研究新型整体加筋薄壁结构稳定性，是评估新结构承载能力、确保结构安全需亟待解决的关键问题之一。然而，因3D编织复合材料细观结构复杂，具有材料与结构同时成型特征，增加了将新材料应用于结构设计与分析的难度。目前，有关3D编织整体加筋壁板稳定性的研究工作还鲜有报导。本项目拟基于3D编织复合材料壁板胞元叠层结构力学模型，采用双尺度思想，提出壁板从细观材料到宏观结构的跨尺度力学建模分析方法，建立3D编织整体加筋壁板在轴压及面内剪切载荷下的的非线性屈曲分析模型，结合试验，研究3D编织整体加筋壁板的屈曲性态，阐明结构的内力分布规律及传载机制，揭示结构的非线性屈曲行为及参数影响规律，为3D编织整体加筋壁板稳定性综合优化设计与分析提供重要依据。

3D编织复合材料整体加筋壁板作为一种轻质高效结构，有望在航空航天工程中得到广泛应用。研究该新材料结构稳定性是评估结构承载能力需亟待解决的重要问题之一。首先，本项目以2D编织整体加筋壁板（包括2D二轴编织1×1、2D三轴）作为切入点，采用双尺度思想，提出了基于细观胞元到宏观壁板结构的跨尺度力学建模方法，结合理论分析和数值建模，建立了轴压2D编织复合材料整体加筋结构的屈曲分析和非线性屈曲分析模型，并选用实例验证了数值建模分析方法的有效性，系统讨论了工艺参数对结构稳定性的影响规律；随即，重点针对3D多向编织复合材料整体加筋结构壁板，系统研究并建立了3D多向编织复合材料细观结构模型和力学性能预测模型；最后，基于胞元叠层结构模型，采用跨尺度力学建模方法，建立了3D编织加筋结构在典型载荷作用下的屈曲分析和非线性屈曲分析模型，系统研究了3D编织整体加筋壁板的非线性屈曲行为，并获得了材料工艺参数对结构稳定性的影响规律。研究表明：编织角和纤维体积含量对结构稳定性具有重要影响。项目研究所提出的相关方法和结果，初步揭示了典型编织复合材料加筋结构的屈曲特性和承载机制，对于新型纺织复合材料加筋结构的综合设计与分析具有重要的参考价值。. 目前，依托本项目已正式在国际期刊发表SCI论文5篇，其中，含JCR二区两篇，另有2篇正准备中。同时，本项目培养研究生2名。