The application of strain gauges as recommended by the ASTM standards provides accurate strain measurements in isotropic materials. However, their use in composite materials becomes more challenging due to their anisotropic nature. In this study, we hypothesized that the use of the distributed sensing system and the three-dimensional digital image correlation, which can average strain along a line and surface, respectively, may account for strain variability in composite materials. This study shows an investigation on the mechanical properties of unidirectional, cross-ply, and angle-ply carbon-epoxy specimens using strain gauges, distributed sensing system, and digital image correlation. The Bhattacharyya distance method was used to provide a preliminary evaluation of the closeness of the three different measurement techniques while the B-basis statistical method was used to analyze the experimental data in order to obtain a more conservative and reliable material parameter compared to the conventional averaged value, recommended by ASTM standards. Finally, a finite element model was created in Ansys Workbench™ as a means of evaluating the implication of a single point strain gauges measurement, versus a line or a surface strain measurement. The finite element analysis investigation was performed at a laminae level using the measured experimental elastic modulus and at a lamina–lamina level in which the elastic modulus of the unidirectional case was used as input in all the laminate configurations. The former analysis showed good agreement between the finite element analysis and all the strain measurement systems with an averaged percentage difference below 5%. The latter analysis showed a higher discrepancy in the measured percentage difference. A comparison between the finite element analysis and the strain gauges measurements showed an overall percentage difference between the range of 10% and 26%. Distributed sensing system and three-dimensional digital image correlation measurements provided an overall percentage difference below 10% for all the specimen configurations with a maximum percentage difference recorded for the longitudinal angle-ply case of approximately 9%.

中文翻译：

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非各向同性材料应变测量系统的精度及其在有限元分析中的不确定度

ASTM 标准推荐的应变计的应用提供了对各向同性材料的准确应变测量。然而，由于它们的各向异性性质，它们在复合材料中的应用变得更具挑战性。在这项研究中，我们假设分布式传感系统和三维数字图像相关性的使用可以分别平均沿线和表面的应变，可以解释复合材料中的应变变异性。本研究展示了使用应变计、分布式传感系统和数字图像相关性对单向、交叉层和角层碳环氧树脂样品的机械性能进行的调查。Bhattacharyya 距离法用于对三种不同测量技术的接近度进行初步评估，而 B 基统计方法用于分析实验数据，以获得比常规平均法更保守、更可靠的材料参数。 ASTM 标准推荐的值。最后，在 Ansys Workbench™ 中创建了一个有限元模型，作为评估单点应变计测量与线或表面应变测量的含义的方法。有限元分析研究是使用测量的实验弹性模量在薄片水平上进行的，在薄片-薄片水平上进行的，其中单向情况的弹性模量用作所有层压结构配置的输入。前一种分析表明，有限元分析与所有应变测量系统之间具有良好的一致性，平均百分比差异低于 5%。后一种分析显示测量的百分比差异有更大的差异。有限元分析和应变仪测量值之间的比较表明，总体百分比差异在 10% 和 26% 之间。分布式传感系统和三维数字图像相关性测量为所有样本配置提供了低于 10% 的总体百分比差异，其中记录的纵向角度层案例的最大百分比差异约为 9%。后一种分析显示测量的百分比差异有更大的差异。有限元分析和应变仪测量值之间的比较表明，总体百分比差异在 10% 和 26% 之间。分布式传感系统和三维数字图像相关性测量为所有样本配置提供了低于 10% 的总体百分比差异，其中记录的纵向角度层案例的最大百分比差异约为 9%。后一种分析显示测量的百分比差异有更大的差异。有限元分析和应变仪测量值之间的比较表明，总体百分比差异在 10% 和 26% 之间。分布式传感系统和三维数字图像相关性测量为所有样本配置提供了低于 10% 的总体百分比差异，其中记录的纵向角度层案例的最大百分比差异约为 9%。