In this work, direct-write piezoelectric transducers (DWTs) were made by spraying piezoelectric poly(vinylidene fluoride-co-trifluoroethylene) coating with comb-shaped electrodes on carbon fibre reinforced polymer (CFRP) plates for drop weight impact damage detection. Their ability and performance were investigated and compared to discrete piezoelectric lead zirconate titanate (PZT) ceramic transducers that were adhesively bonded on the same CFRP plate. Guided wave signals were acquired with different combinations of actuator-sensor involving DWT, PZT and laser ultrasonic excitation, in pitch-catch configuration. DWTs allowed consistency and simplified signal interpretation due to an effective mode selection (A₀ or S₀ mode) with wavelengths of 10 and 12 mm. PZTs generated stronger but much more complex signals and mode selection with a larger wavelength (20 mm). The configuration with PZT as actuator and DWT as receiver showed the highest signal amplitude changes of A₀ or S₀ mode, allowing efficient detection of damage introduced by a 31 J impact. Further ultrasonic B- and C-scans revealed a 27 mm long crack on the plate’s backside developed in addition to internal cracks and delaminations of about 34 mm in length. For realizing contactless ultrasound excitation, a neodymium-doped yttrium aluminium garnet laser (wavelength of 1064 nm, 5.4 ns pulses) was used to replace the surface-mounted brittle PZT. The combination of the broadband laser excitation with the DWTs as sensors achieved more reliable damage detection than equivalent PZTs, attributed to DWT’s effective single mode selection. In addition to reduced weight, the polymeric coated DWTs allow large area implementation (scaling up), even on curved surfaces due to their flexibility and conformability, in contrast to adhesively bonded discrete transducers.

在这项工作中，通过在碳纤维增强聚合物（CFRP）板上喷涂带有梳状电极的压电聚（偏二氟乙烯-三氟乙烯）涂层制成直写式压电换能器（DWT），用于落锤冲击损伤检测。研究了它们的能力和性能，并将其与粘合在同一 CFRP 板上的离散压电锆钛酸铅 (PZT) 陶瓷换能器进行了比较。在一发一收配置中，使用涉及 DWT、PZT 和激光超声激发的不同执行器-传感器组合获取导波信号。由于有效的模式选择（A ₀或 S ₀模式），波长为 10 和 12 毫米。PZT 产生更强但更复杂的信号和具有更大波长（20 毫米）的模式选择。以 PZT 作为执行器和 DWT 作为接收器的配置显示了 A ₀或 S ₀的最高信号幅度变化模式，允许有效检测由 31 J 撞击引起的损坏。进一步的超声波 B 和 C 扫描显示，除了约 34 毫米长的内部裂纹和分层外，板背面还出现了 27 毫米长的裂纹。为了实现非接触式超声激发，使用掺钕钇铝石榴石激光器（波长为 1064 nm，5.4 ns 脉冲）代替表面贴装的脆性 PZT。由于 DWT 有效的单模选择，宽带激光激发与作为传感器的 DWT 的组合实现了比等效 PZT 更可靠的损伤检测。除了减轻重量外，与粘合剂粘合的离散换能器相比，聚合物涂层 DWT 允许大面积实施（放大），即使在弯曲表面上也是如此，因为它们具有灵活性和适应性。