Barely visible impact damage (BVID) is one of the most dangerous types of structural damage in composites, since in most practical cases the application of advanced non-destructive testing (NDT) methods is required to detect and identify it. Due to its character of propagation, there are minor signs of structural damage on a surface, while the internal damage can be broad and complex both in the point of view of fracture mechanisms and resulting geometry of damage. The most common NDT method applied e.g., in aircraft inspections is ultrasonic testing (UT), which enables effective damage detection and localization in various environments. However, the results of such inspections are usually misestimated with respect to the true damage extent, and the quantitative analysis is biased by an error. In order to determine the estimation error a comparative analysis was performed on NDT results obtained for artificially damaged carbon fiber-reinforced composite structures using two UT methods and X-ray computed tomography (CT). The latter method was considered here as the reference one, since it gives the best spatial resolution and estimation accuracy of internal damage among the available NDT methods. Fusing the NDT results for a set of pre-damaged composite structures with various energy values of impact and various types of impactor tips applied for introducing damage, the evaluation of estimation accuracy of UT was possible. The performed analysis allowed for evaluation of relations between UT and X-ray CT NDT results and for proposal of a correcting factor for UT results for BVID in the analyzed composite structures.

中文翻译：

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基于超声测试和X射线计算机断层扫描结果融合的复合结构冲击损伤评估。

几乎可见的冲击破坏（BVID）是复合材料中最危险的结构破坏类型之一，因为在大多数实际情况下，需要使用高级无损检测（NDT）方法进行检测和识别。由于其传播特性，在表面上几乎没有结构损坏的迹象，而从断裂机理和最终的损坏几何形状来看，内部损坏可能既广泛又复杂。例如，在飞机检查中使用的最常见的无损检测方法是超声测试（UT），它可以在各种环境中进行有效的损坏检测和定位。但是，这种检查的结果通常相对于真实的损坏程度被错误估计，并且定量分析存在误差。为了确定估计误差，对使用两种UT方法和X射线计算机断层扫描（CT）对人为破坏的碳纤维增强复合结构获得的NDT结果进行了比较分析。后者被认为是参考方法，因为它在可用的NDT方法中提供了最佳的空间分辨率和内部损伤的估计精度。将无损检测结果融合到一组预先损坏的复合结构中，该复合结构具有各种冲击能量值和各种类型的冲击器尖端（用于引入损伤），可以评估UT的估计精度。进行的分析可以评估UT和X射线CT NDT结果之间的关系，并可以为分析的复合结构中BVID的UT结果提出校正因子的建议。