[2C5] Comparing different non-destructive evaluation modalities for the assessment of out-of-plane waviness in carbon fibre-reinforced plastics
R Gomes¹, E Mohseni¹, V Maes², M Contino³, S G Pierce¹, K Burnham¹, R Vithanage¹,
C MacLeod¹,
G Munro⁴ and T O’Hare⁴
¹University of Strathclyde, UK
²University of Bristol, UK
³Adaptix NDE UK Ltd, UK
⁴Spirit AeroSystems, UK
Out-of-plane waviness is a common defect that reduces the tensile and compressive strength of carbon fibre and uses eddy current array testing (ECAT), phased array ultrasonic testing (PAUT) and X-ray digital tomosynthesis (DT) to detect and characterise ply wrinkles. Nine unidirectional carbon fibre prepreg coupons were fabricated with controlled ply wrinkles, yielding waviness amplitudes from 0.13 mm to 1.31 mm.
ECAT, implemented using two commercial array probes at frequencies of 500-3000 kHz, efficiently detected wrinkles with severity factors ≥0.03, though geometric characterisation of the wrinkle morphology was limited. PAUT, using full matrix capture at probe frequencies of 5 MHz, 7.5 MHz and 10 MHz, followed by total focusing method (TFM) for B-scan image reconstruction, provided precise wrinkle imaging and the structural tensor image processing technique was employed to quantify the orientation of the internal plies affected by the induced fibre wrinkle by measuring the gradients contained in the TFM B-scan instantaneous phase image. Overall, 7.5 MHz delivered the most accurate out-of-plane angle assessment. X-ray DT conducted at 35 kV and 140 μA with variable exposure times enabled rapid volumetric evaluation via intensity profiling but struggled with wrinkles <0.30 mm due to spatial resolution constraints.
ECAT, implemented using two commercial array probes at frequencies of 500-3000 kHz, efficiently detected wrinkles with severity factors ≥0.03, though geometric characterisation of the wrinkle morphology was limited. PAUT, using full matrix capture at probe frequencies of 5 MHz, 7.5 MHz and 10 MHz, followed by total focusing method (TFM) for B-scan image reconstruction, provided precise wrinkle imaging and the structural tensor image processing technique was employed to quantify the orientation of the internal plies affected by the induced fibre wrinkle by measuring the gradients contained in the TFM B-scan instantaneous phase image. Overall, 7.5 MHz delivered the most accurate out-of-plane angle assessment. X-ray DT conducted at 35 kV and 140 μA with variable exposure times enabled rapid volumetric evaluation via intensity profiling but struggled with wrinkles <0.30 mm due to spatial resolution constraints.
