Sandwich panels consisting of two Carbon Fibre Reinforced Polymer (CFRP) outer skins and an aluminium honeycomb core are a common structure of surfaces on commercial aircraft due to the beneficial strength–weight ratio. Mechanical defects such as a crushed honeycomb core, dis-bonds and delaminations in the outer skins and in the core occur routinely under normal use and are repaired during aerospace Maintenance, Repair and Overhaul (MRO) processes. Current practices rely heavily on manual inspection where it is possible minor defects are not identified prior to primary repair and are only addressed after initial repairs intensify the defects due to thermal expansion during high temperature curing. This paper reports on the development and characterisation of a technique based on conductive thermography implemented using an array of single point temperature sensors mounted on one surface of the panel and the concomitant induced thermal profile generated by a thermal stimulus on the opposing surface to identify such defects. Defects are classified by analysing the differential conduction of thermal energy profiles across the surface of the panel. Results indicate that crushed core and impact damage are detectable using a stepped temperature profile of 80 ${}^{\circ }$C The method is amenable to integration within the existing drying cycle stage and reduces the costs of executing the overall process in terms of time-to-repair and manual effort.

中文翻译：

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导电热成像和接触式传感器检测航空航天夹芯复合板中的效应

由于有益的强度重量比，由两个碳纤维增强聚合物（CFRP）蒙皮和一个铝蜂窝芯组成的夹心板是商用飞机表面的常见结构。在正常使用情况下，通常会发生机械缺陷，例如蜂窝芯破碎，外表层和芯中的粘结和分层，这些缺陷通常在航空航天维护，修理和大修（MRO）过程中进行修复。当前的实践严重依赖于人工检查，在这种情况下，可能在初次修复之前未发现较小的缺陷，只有在初次修复加剧了由于高温固化过程中的热膨胀引起的缺陷之后才解决。本文报告了基于导电热成像技术的开发和表征，该技术使用安装在面板一个表面上的单点温度传感器阵列实现，并通过对置表面上的热刺激产生伴随感应的热分布，以识别此类缺陷。通过分析整个面板表面的热能分布的差异传导，可以对缺陷进行分类。结果表明，使用80的阶梯式温度曲线可以检测到压碎的芯和冲击损伤 通过分析整个面板表面的热能分布的差异传导，可以对缺陷进行分类。结果表明，使用80的阶梯式温度曲线可以检测到压碎的芯和冲击损伤 通过分析整个面板表面的热能分布的差异传导，可以对缺陷进行分类。结果表明，使用80的阶梯式温度曲线可以检测到压碎的芯和冲击损伤${}^{\circ }$C该方法适合于整合到现有的干燥循环阶段中，并减少了维修时间和人工工作，从而降低了执行整个过程的成本。