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为了深入探究复合材料层合板结构的损伤机理和损伤演化,应用声发射技术和图像相关技术同步实时监测含孔碳纤维复合材料层合板试样在静拉伸过程中的损伤演化。实验结果表明,试样表面应变场呈现局部化特征。对应变集中带在加载方向的应变值进行了统计分析,获得了应变场的特征统计量(标准差)随加载的演化模型。层合板损伤时产生声发射信号的峰值频率大小能够有效区分复合材料的损伤模式,由此,建立了基于损伤模式累积声发射数的损伤演化模型。通过对应变场演化模型和声发射损伤演化模型的分析,可以将复合材料的损伤演化分为损伤初始阶段、损伤平稳扩展期、损伤严重阶段三个部分。统计分析结果表明:在损伤严重阶段,基于声发射事件数的各种损伤的损伤变量和局部应变场标准差快速增长,因此局部应变场统计标准差可以作为后期局部损伤严重程度的识别指标。
In order to further investigate the damage mechanism and damage evolution of composite laminates, acoustic emission and image-related techniques were used to simultaneously monitor the damage evolution during the static drawing process of the samples containing porous carbon fiber composite laminates. The experimental results show that the strain field on the specimen presents a localized characteristic. The strain values in the loading direction of the strain concentration zone are statistically analyzed, and the evolutionary model of the characteristic statistic (standard deviation) of the strain field with loading is obtained. The peak frequency of acoustic emission signals generated when the laminate is damaged can effectively distinguish the damage modes of the composites. Therefore, a damage evolution model based on the cumulative acoustic emission number of the damage modes is established. Based on the analysis of the evolution model of the strain field and the acoustic emission damage evolution model, the damage evolution of the composite can be divided into three parts: the initial stage of injury, the stable stage of injury extension and the serious stage of injury. The results of statistical analysis show that the standard deviation of local strain field and local strain field can be used as the identification index of the severity of local lesion in the severe damage stage.