温度对复合材料层合板疲劳分层扩展行为的影响机理研究

Temperature has significant effects on fatigue delamination in carbon fibre/epoxy composite laminates. Even though a great effort has been made in the past to explore temperature effects on fatigue delamination in composite laminates, no general consensus has been achieved yet regarding the nature of these effects, which can severely prohibit the effective use of these materials in the next generation civil aircraft. As a result, it is important and crucial to investigate fatigue delamination in composite laminates at different temperatures. The aims of present study are therefore summarized as to have in-depth understanding on the micro-mechanisms related to temperature effects on fatigue delamination, and to develop a new fatigue criterion as well as corresponding numerical model to accurately represent fatigue delamination in carbon fibre/epoxy composite laminates at different temperatures. In the first step, the micro-mechanisms related to temperature effects on fatigue delamination will be elaborately explored and discussed via in-situ characterization on damage evolution around delamination front and fibre bridging performance in the bridging region. And the micromechanical model proposed in literature will be employed to have further information of temperature effects on the performance of fibre bridging. Furthermore, the energy dissipation behaviors of fibre-bridged fatigue delamination at different temperatures will be analyzed and compared via fatigue data derived from experiments. As a result, the temperature effects on energy dissipation in fatigue delamination as well as corresponding micro-mechanisms can be well investigated. In the second step, an inverse semi-experimental method will be developed to quantify the bridging laws in fatigue delamination at different temperatures. And a new bridging law, taking temperature effects into account, will be proposed to appropriately characterize this shielding mechanism and to accurately calculate the strain energy release rate during fatigue delamination. In the third step, an appropriate crack control parameter, which can best represent fatigue damage evolution and corresponding energy dissipation, will be examined and used for the development of a new fatigue delamination criterion (i.e. a new modified Paris law). And a numerical model based on this criterion will be developed to accurately determine fatigue delamination at different temperatures. Finally, fatigue delamination behaviors of carbon fibre/epoxy composite laminates at different temperatures can be well explored.

温度对复合材料的疲劳分层扩展行为有重要影响，但温度对疲劳分层扩展的影响机理尚不明确，这不利于复合材料在我国新一代民航客机中的有效应用。本项目以申请人前期研究为基础，通过对不同温度条件下碳纤维环氧树脂基复合材料的疲劳分层扩展行为进行研究，探索温度对疲劳分层扩展的影响机理，揭示不同温度条件下复合材料的疲劳分层扩展规律。首先，基于疲劳分层扩展试验和扫描电镜原位试验分析观测，并结合微观力学模型分析和损伤机理研究，探索温度对疲劳分层扩展典型微观损伤演化及纤维桥联作用形式的影响，明确温度对疲劳分层扩展中能量耗散的影响；其次，将试验测试和数值反演分析相结合，对疲劳分层扩展中的桥联法则进行研究，建立考虑温度影响的桥联法则；再次，对有效反映能量耗散和损伤演化的疲劳裂纹扩展控制参数进行分析，建立新的改进的Paris准则和数值模拟预测模型，对碳纤维环氧树脂基复合材料在不同温度条件下的疲劳分层扩展行为进行研究。

先进复合材料以其优异的力学性能已经广泛应用于航空航天领域，分层扩展是导致复合材料结构失效的主要原因，温度对分层扩展行为存在显著影响。本项目以分层扩展试验研究为基础，结合理论分析和损伤机理分析，重点对不同温度条件下复合材料的疲劳分层扩展行为开展研究，明确了温度对疲劳分层扩展的影响规律，阐明了温度对疲劳分层扩展中纤维桥联的影响机理。通过开展原位试验分析观测和微观力学模型分析，揭示了纤维桥联的损伤失效机制，明确了桥联法则的分布规律，建立了有效的分层扩展分析预测模型，实现了纤维桥联作用下复合材料分层扩展行为的准确预测。基于疲劳裂纹扩展相似性原理，提出新的疲劳裂纹扩展控制参数，建立了新的疲劳分层扩展准则，实现了复合材料疲劳分层扩展行为的有效描述，揭示了复合材料的疲劳分层扩展规律。