Carbon fiber reinforced polymers (CFRPs) with large thickness (≥20 mm) are being extensively used for aerospace structures, and are prone to the manufacturing and in-service defects due to the complexity and difficulty of manufacturing. This study addresses an intensive interrogation of multi-parameter optimization towards a high-quality ultrasonic total focusing method (TFM) imaging for diverse and multiple defects in crossply CFRP. Firstly, material parameters of unidirectional laminate are inversely constructed based on Christoffel equation by inputting the experimentally measured wave speed, based on which the wave speed and homogenization region for the crossply CFRP are obtained with the Floquet wave theory. Then, the wave propagation at crossply CFRP with preset side drilled holes (SDHs) at depths of 4 mm and 12 mm is modelled, from which the full matrix data are extracted for TFM imaging using multiple parameter optimization, including wave velocity correction, propagation restriction angle, and wave central frequency. With the proposed signal-to-noise ratio as the criterion of TFM imaging quality, the combined parameters for optimized imaging are sorted out, which are strongly related to the feature of propagating and non-propagating waves calculated with the Floquet wave homogenization theory. A further experimental validation is performed to image multiple SDHs and delamination with size over 2 mm and depths covering 2.5 mm to 17.5 mm. This systematic analysis of parameter optimization for TFM imaging in thick CFRP sets up the foundation for the TFM towards a real engineering application of CFRP detection.

大厚度（≥20 mm）的碳纤维增强聚合物（CFRPs）被广泛用于航空航天结构，但由于制造的复杂性和难度，容易出现制造和使用中的缺陷。本研究针对正交 CFRP 中的多种缺陷，针对高质量超声全聚焦法 (TFM) 成像，针对多参数优化进行了深入研究。首先，输入实验测得的波速，基于Christoffel方程反构造单向层合板的材料参数，在此基础上利用Floquet波理论得到正交碳纤维复合材料的波速和均匀化区域。然后，对深度为 4 mm 和 12 mm 的预设侧钻孔 (SDH) 的交叉 CFRP 处的波传播进行建模，使用多参数优化（包括波速校正、传播限制角和波中心频率）从中提取全矩阵数据用于 TFM 成像。以提出的信噪比作为TFM成像质量的标准，整理出优化成像的组合参数，这些参数与Floquet波均匀化理论计算的传播波和非传播波的特征密切相关。执行进一步的实验验证以对尺寸超过 2 毫米且深度覆盖 2.5 毫米至 17.5 毫米的多个 SDH 和分层进行成像。这种对厚 CFRP 中 TFM 成像参数优化的系统分析为 TFM 走向 CFRP 检测的实际工程应用奠定了基础。