To be able to track the deformation of fibers in composite laminates subject to high strain bending and to study any changes that occur due to elevated temperature hold, an experimental technique using micron scale X-ray computed tomography (micro-CT) was developed and is reported here. A lab based X-ray micro-CT system with resolution as low as 0.7 μ m was used to scan an approximately 0.76 × 0.76 × 0.27 mm volume of a 0.27 mm thick unidirectional carbon fiber/epoxy matrix composite laminate. Long scans of 16 hours at low energy, 40 kV, were needed to yield low noise, clear CT images. The laminate is bent to a radius of curvature of approximately 8.2 mm and held statically in a 3D printed fixture. Since the fixture is in the beam path it is important that it have low and uniform X-ray absorption. Several materials were tried, resulting in the choice of polyamide for the 3D printed fixture. Treating fiber cross sections as particles and adapting an algorithm designed for tracking particle trajectories, individual fibers in the deformed state are identified and their coordinates mapped out. Analysis of the fibers shows no measurable change to the fiber curvatures before and after being held at 80 ∘ C for one hour.

中文翻译：

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高应变弯曲下复合层压板中纤维的显微 CT 成像

为了能够跟踪复合材料层压板中纤维在高应变弯曲下的变形并研究由于高温保持而发生的任何变化，开发了一种使用微米级 X 射线计算机断层扫描 (micro-CT) 的实验技术，并且在这里报道。使用分辨率低至 0.7 μm 的实验室 X 射线微 CT 系统扫描约 0.76 × 0.76 × 0.27 mm 体积的 0.27 mm 厚单向碳纤维/环氧树脂基复合材料层压板。需要在 40 kV 低能量下进行 16 小时的长时间扫描，才能产生低噪声、清晰的 CT 图像。层压板弯曲到大约 8.2 毫米的曲率半径，并静态固定在 3D 打印固定装置中。由于夹具位于光束路径中，因此它具有低且均匀的 X 射线吸收是很重要的。尝试了几种材料，导致 3D 打印夹具选择聚酰胺。将纤维横截面视为粒子并采用设计用于跟踪粒子轨迹的算法，识别变形状态的单个纤维并绘制它们的坐标。对纤维的分析表明，在 80 ∘ C 下保持一小时之前和之后，纤维曲率没有可测量的变化。