ABSTRACT Glass or carbon fibre-reinforced polymer (FRP) structures have attained a relevant role in modern production thanks to their lightweight, high resistance to corrosion and fatigue, and relative ease of manufacturing complex shapes. Nevertheless, several types of defects, such as voids, matrix fractures, delaminations and impact damages, which might significantly reduce the useful life of composite-made structural components, are often difficult to be identified. Conventional non-destructive methods, such as ultrasonic testing, are routinely used to monitor composite constructions with good results. However, an inspection of large structures requires alternative and faster NDT methods. Among these, air-coupled ultrasonic testing (ACUT) and active infrared thermography (AIRT) are generally considered the most promising ones. In this paper, ACUT and AIRT have been compared by performing experimental tests on two reference composite panels with synthetic defects. Polytetrafluoroethylene (PTFE) and aluminium inserts with different sizes and located at various depths have been used as artificial defects. The relative merits and drawbacks of the two techniques have been highlighted in terms of defect size sensitivity, maximum depth that can be detected, and thermo-physical properties of the reflector. A qualitative and quantitative analysis has been carried out to evaluate the ability of the two techniques in retrieving the actual size of the subsurface defects.

中文翻译：

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空气耦合超声检测与主动热成像在复合材料缺陷识别中的比较

摘要 玻璃或碳纤维增强聚合物 (FRP) 结构由于重量轻、抗腐蚀和抗疲劳性高以及制造复杂形状相对容易，因此在现代生产中发挥了重要作用。然而，几种类型的缺陷，如空隙、基体断裂、分层和冲击损伤，可能会显着降低复合材料结构部件的使用寿命，通常难以识别。常规的非破坏性方法，例如超声波检测，通常用于监测复合结构，并取得良好的效果。然而，大型结构的检查需要替代且更快的 NDT 方法。其中，空气耦合超声检测（ACUT）和主动红外热成像（AIRT）通常被认为是最有前途的。在本文中，ACUT 和 AIRT 已通过对具有合成缺陷的两个参考复合板进行实验测试进行了比较。不同尺寸和不同深度的聚四氟乙烯 (PTFE) 和铝嵌件已被用作人工缺陷。这两种技术的相对优点和缺点在缺陷尺寸灵敏度、可检测的最大深度和反射器的热物理特性方面都得到了强调。已经进行了定性和定量分析以评估这两种技术在检索地下缺陷的实际尺寸方面的能力。不同尺寸和不同深度的聚四氟乙烯 (PTFE) 和铝嵌件已被用作人工缺陷。这两种技术的相对优点和缺点在缺陷尺寸灵敏度、可检测的最大深度和反射器的热物理特性方面都得到了强调。已经进行了定性和定量分析以评估这两种技术在检索地下缺陷的实际尺寸方面的能力。不同尺寸和不同深度的聚四氟乙烯 (PTFE) 和铝嵌件已被用作人工缺陷。这两种技术的相对优点和缺点在缺陷尺寸灵敏度、可检测的最大深度和反射器的热物理特性方面都得到了强调。已经进行了定性和定量分析以评估这两种技术在检索地下缺陷的实际尺寸方面的能力。