含孔复合材料层合板静拉伸损伤演化的实验和表征方法

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。

Experimental Study and Characterization Method of Damage Evolution for Composite Laminate with Open Hole Subjected to Static Tensile Loading

In order to get deeper understanding of damage mechanism and evolution of composite laminate structure,based on acoustic emission technology and digital image correlation (DIC)method,the damage evolution of carbon-fiber composite laminate specimen with open hole was realtime synchronously monitored during static tensile loading process.Experimental results show that the strain field on specimen surface presents localization characteristics;statistical analysis of strain value in strain concentration band along loading direction was carried out,based on which,the evolution model of strain field characteristic statistic (standard deviation) along with the loading was obtained.The peak frequency distribution of AE signals generated by laminate damage can effectively identify the damage mode of composite materials,therefrom,damage evolution model was established,based on acoustic emission numbers cumulated by damage model.Through the analysis of both strain field evolution model and AE damage evolution model,the damage evolution of composite material can be divided into three stages:the initial damage stage,the stable propagation stage and the serious damage stage.Analysis results show that on serious damage stage,the damage variables and standard deviation of local strain field rapidly grow along with the AE event numbers,so the statistical standard deviation of local strain field can be used as identification index of the severity of local damage on later stage.