Data underlying the article: Damage accumulation analysis of CFRP cross-ply laminates under different tensile loading rates

The loading rate effect on both mechanical properties and damage accumulation process of cross-ply carbon fiber-polymer laminates under tensile loading was investigated. In-situ edge observations, Acoustic Emission and Digital Image Correlation techniques were utilized simultaneously to monitor the state of damage in real time. Results showed that the axial modulus and strength were less sensitive to loading rates than failure strain, which increased with the decrease of the loading rate. In the viewpoint of damage accumulation process, high density and uniform distribution of transverse matrix cracks, and H-shape crack patterns, incorporating inter-laminar cracks, were more likely to occur at low loading rates while variable crack spacing occurred at higher rates. When loading rates were lower than a certain level, maximum transverse matrix crack density decreased slightly due to the restriction of relatively widely generated inter-laminar cracks. Furthermore, the cumulative acoustic emission energy of low-frequency signals was linearly correlated to transverse matrix crack density, providing a promising way to quantify crack accumulation in real time. Finally, spatial consistence was observed between transverse matrix cracks at edges and stress concentrations at the exterior 0 ply, and the peaks of axial strain at local concentration regions locate either near the newest cracks or at the place with minimum crack spacing.

本研究针对拉伸载荷下正交铺层碳纤维-聚合物层合板的力学性能与损伤累积过程受加载速率的影响开展了实验探究。研究同步采用原位边缘观测、声发射（Acoustic Emission）与数字图像相关（Digital Image Correlation）技术，实时监测损伤演化状态。实验结果表明，轴向弹性模量与强度对加载速率的敏感性弱于断裂应变，而断裂应变随加载速率降低而增大。从损伤累积过程来看，低加载速率下更易出现横向基体裂纹密度高且分布均匀的特征，以及伴随层间裂纹的H形裂纹形貌；而高加载速率下则会出现裂纹间距不均的现象。当加载速率低于某一临界值时，由于大量生成的层间裂纹产生抑制作用，最大横向基体裂纹密度会出现小幅下降。此外，低频信号的累计声发射能量与横向基体裂纹密度呈线性相关，为实时量化裂纹累积演化提供了可行途径。最后，研究发现边缘处的横向基体裂纹与外层0°铺层的应力集中区域存在空间一致性，局部集中区域的轴向应变峰值要么位于最新形成的裂纹附近，要么处于裂纹间距最小的位置。