Although ultrasonic pulse-echo C-scanning is a mature non-destructive evaluation technique for imaging internal damage in composite structures, a major impediment of obtaining a full characterization of the internal damage state is delamination shadowing effects. Specifically, shadowing refers to regions of interest that are behind other delamination planes or discontinuities with respect to the scanning surface. The delamination planes block ultrasonic wave transmission and the regions of interest are thus hidden (i.e. shadowed) from the scan. A methodology has been developed to expand ultrasonic scan data of impacted composites by utilizing damage morphology information that is well established in the composite impact research community, such as matrix cracks bounding delaminations, to estimate shadowed delamination information and matrix cracking. First, impacted flat composite plates were C-scanned by pulse-echo ultrasonic and the results were segmented by depth of damage to establish interface-by-interface delamination information. These delaminations were then fit by bounding lines representing the fiber/matrix crack directions defined by the orientations of plies adjacent to each interface to estimate the shadowed portion of the delamination results. The area inside this boundary was added to the original ultrasonic delamination area to create an estimation of the full delamination state at each shadowed interface. Additionally, because this extension method is based on the interactions between delaminations and matrix cracking, this extension method provides an approximation of the matrix cracking of adjacent plies. Results were compared with X-ray computed tomography scans to assess the effectiveness of the extension method.

中文翻译：

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通过 X 射线 CT 验证的撞击复合材料的超声 C 扫描中的阴影分层区域估计

尽管超声脉冲回波 C 扫描是一种成熟的无损评估技术，用于对复合结构中的内部损伤进行成像，但获得内部损伤状态完整表征的主要障碍是分层阴影效应。具体而言，阴影是指相对于扫描表面位于其他分层平面或不连续性后面的感兴趣区域。分层平面阻止超声波传输，因此对扫描隐藏（即遮蔽）感兴趣的区域。已经开发出一种方法来扩展冲击复合材料的超声扫描数据，该方法利用在复合材料冲击研究界已经确立的损伤形态信息，例如边界分层的基体裂纹、估计阴影分层信息和基体开裂。首先，冲击复合平板用脉冲回波超声波 C 扫描，结果按损伤深度分割，以建立逐个界面的分层信息。然后通过边界线拟合这些分层，该边界线代表由与每个界面相邻的层的方向定义的纤维/基质裂纹方向，以估计分层结果的阴影部分。该边界内的区域被添加到原始超声分层区域，以创建每个阴影界面处完全分层状态的估计。此外，由于这种扩展方法基于分层和基体开裂之间的相互作用，因此该扩展方法提供了相邻层的基体开裂的近似值。