Monitoring of extreme dynamic loadings on composite materials with high temporal and spatial resolution provides an important insight into the understanding of the material behaviour. Quantitative measurement of the surface strain at the first moments of the impact event may reveal the initiation of the failure mechanisms leading to damage. For this purpose, we developed a shearography instrument for strain measurements during a severe impact event at µs temporal resolution. This paper presents the design, development and experimental measurement of the surface strain during an impact on aluminium and composite samples. The final design realises measurements of the in- and out-of-plane surface strain components to improve coupling of experimental data with the numerical models. The experiments on aluminium and composite specimens revealed the main elastic material response to be in the first 1-2 µs after the impact followed by the initiation and propagation of flexural waves causing in- and out-of-plane deformation. Further analysis of the wavefronts will be used as input and validation data for new numerical and analytical models of the impact response of composites and for validation of other experimental techniques as acoustic emission and embedded piezo sensors.

The set of technical parameters of the developed shearography instrument makes it one of the most extreme applications of shearography for material characterisation. The framework for this work is the “EXTREME Dynamic Loading – Pushing the Boundaries of Aerospace Composite Material Structures” Horizon 2020 project.

以高的时间和空间分辨率监视复合材料上的极端动态载荷，可为了解材料行为提供重要的见识。冲击事件开始时对表面应变的定量测量可以揭示导致损坏的破坏机理的启动。为此，我们开发了一种用于在严重撞击事件中以µs时间分辨率测量应变的剪切成像仪。本文介绍了铝和复合材料试样撞击过程中表面应变的设计，开发和实验测量。最终设计实现了平面内和平面外表面应变分量的测量，以改善实验数据与数值模型的耦合。在铝和复合材料样品上进行的实验表明，主要的弹性材料响应发生在撞击后的前1-2 µs，随后是弯曲波的引发和传播，从而引起面内和面外变形。波前的进一步分析将用作复合材料冲击响应的新数值和分析模型的输入和验证数据，以及其他实验技术（如声发射和嵌入式压电传感器）的验证。

先进的剪切成像仪的技术参数集使其成为用于材料表征的剪切成像的最极端应用之一。这项工作的框架是“极端动态载荷-突破航空复合材料结构的边界” Horizo​​n 2020项目。