Four different methods to experimentally determine the J\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {J}$$\end{document}-curve of quasi-brittle materials are analysed and discussed in this work. The first two methods measure the integral of the cohesive law, J(ω)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {J}(\omega )$$\end{document}, from an initial notch. However, the correct definition of the notch geometry is of critical importance for an accurate identification of the cohesive law. The other two methods measure J(ω)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {J}(\omega )$$\end{document} when the crack is propagating with a fully-developed cohesive zone. In this case, the cohesive law is obtained by determining the crack opening displacement along the fracture process zone without requiring information about the geometry of the initial notch. The four methods are discussed highlighting the corresponding advantages, limitations and required experimental results. Then, the results of the four methods are compared and validated by considering the experimental results of the Compact Tension test of a quasi-isotropic carbon fibre composite laminate. Finally, some recommendations are given on which of the four methods is the most appropriate to characterise the material J(ω)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {J}(\omega )$$\end{document} law based on the available measuring techniques.

中文翻译：

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准脆性复合材料$$\mathcal {J}$$-曲线的实验测定

四种不同的方法来实验确定 J\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {J}$$\end{document} - 准脆性材料的曲线在这项工作中进行了分析和讨论。前两种方法测量内聚律的积分，J(ω)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \ usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {J}(\omega )$$\end{document}，从最初的缺口开始。然而，凹口几何形状的正确定义对于准确识别内聚定律至关重要。另外两种方法测量 J(ω)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{ upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {J}(\omega )$$\end{document} 当裂缝以完全发展的内聚区传播时。在这种情况下，内聚定律是通过确定沿断裂过程区的裂纹张开位移而获得的，而无需有关初始缺口几何形状的信息。讨论了四种方法，重点介绍了相应的优点、局限性和所需的实验结果。然后，通过考虑准各向同性碳纤维复合材料层压板的紧凑拉伸试验的实验结果，对四种方法的结果进行了比较和验证。最后，就四种方法中哪一种最适合表征材料给出了一些建议 J(ω)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{ amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {J}(\omega )$$\end{document}法基于可用的测量技术。