CFRP复杂几何结构超声表面契合法缺陷检测

碳纤维增强树脂基复合材料(Carbon fiber reinforced plastics，CFRP)复杂几何结构(即R区)的声传播规律复杂，缺陷检测困难。为提高相控阵超声线性阵列探头的检测能力，以热压固化制备的T700/环氧树脂T形长桁为研究对象，从有限元建模与验证、水程优选与缺陷成像、面积型缺陷定量与覆盖范围三个方面研究了超声表面契合法(Surface adaptive ultrasonic，SAUL)检测的关键技术。结果表明：模拟和试验中分层缺陷均能有效识别，但试样两侧肋板表面和层间界面反射回波过强，成像噪声大，定量困难；对检测中水程进行优选后，两侧肋板反射回波基本消失，缺陷成像完整清晰，成像质量明显提升。在此基础上提出了R区面积型缺陷尺寸的定量方法及检测覆盖范围计算方法，实现了R区深度 1.5 mm、周向长度 4.5 mm分层缺陷的定量检测，深度定量误差6.7%，周向长度定量误差4.4%，满足工程需求。研究结果将为复合材料缺陷精准检测提供支持。

Surface Adaptive Ultrasonic Testing on Defects in CFRP Radii

The wave propagation behavior is complicated in the radii of carbon fiber reinforced plastics(CFRP), and thus the precise nondestructive testing on defects becomes quite difficult. To improve the testing ability with an ultrasonic linear array probe, surface adaptive ultrasonic (SAUL) testing is performed on a T stringer manufactured with T700/epoxy resin by hot compression curing. Three key issues are studied, including the finite element modeling and experimental verification, the water distance selection and defect imaging, and the quantification methods of planar defects and coverage range in radii. It is indicated that a preset delamination can be effectively identified in both simulation and experiment, but is difficult to be quantified. This is mainly attributed to the strong superficial and interfacial reflection echoes from the ribbed plates, which result in significant noise and poor imaging ability. After optimization of the water distance in SAUL testing, the reflection from the ribbed plates disappears to a great extent, and high-quality imaging of the delamination is obtained. In further, the methods for the sizing of a planar defect and coverage range in radii are proposed. A delamination with a 1.5 mm depth and 4.5 mm length in circumference is quantitatively detected. The errors are 6.7% in depth and 4.4% in circumferential length respectively, which could meet the requirements of engineering applications. The results would give support for the precise inspection of CFRP components.