Characterisation of carbon fibre-reinforced polymer composites through radon-transform analysis of complex eddy-current data

Abstract

Maintaining the correct fibre orientations and stacking sequence in carbon-fibre reinforced polymers (CFRP) during manufacture is essential for achieving the required mechanical properties of a component. This paper presents and evaluates a method for the rapid characterisation of the fibre orientations present in CFRP structures, and the differentiation of different stacking sequences, through the Radon-transform analysis of complex-valued eddy-current testing (ECT) inspection data. A high-frequency (20 MHz) eddy-current inspection system was used to obtain 2D scans of a range of CFRP samples of differing ply stacking sequences. The complex electrical impedance scan data was analysed using Radon-transform techniques to quickly and simply determine the dominant fibre orientations present in the structure. This method is compared to 2D-fast Fourier transform (2D-FFT) analysis of the same data and shown to give superior quantitative results with comparatively fewer computational steps and corrections. Further analysis is presented demonstrating and examining a method for preserving the complex information inherent within the eddycurrent scan data during Radon-transform analysis. This investigation shows that the real and imaginary components of the ECT data encode information about the sacking sequence allowing the distinction between composites with different stacking structures. This new analysis technique could be used for in-process analysis of CFRP structures as a more accurate characterisation method, reducing the chance of costly manufacturing errors.

Evaluation of detectability of differential type probe using directional eddy current for fibre waviness in CFRP

“…A unidirectional CFRP plate with a 135 × 135 × 1.44 mm 3 was fabricated with six plies of prepreg (Torayca P3252S-25, Toray Industries Inc.). The six prepregs were laminated on the base plate and compressed at 0.5 MPa and heated at 130°C for 60 min by using a hot press machine (AH-2003, ASONE Co.).…”

“…By contrast, eddy current testing (ECT) can be suited to those fibre-related defects because it is susceptible to the variation of electric resistance. For instance, it is reported that fibre orientation [1][2][3][4][5][6][7][8][9][10], misorientation (off-axis) [11][12][13][14][15] and fibre waviness [16][17][18][19][20][21] are detectable fibre-related defects by ECT. Additionally, some researchers have reported that ECT with higher frequency has the potential to non-destructively evaluate the hardening degree of matrix resin in FRP during the curing process of products [21][22][23].…”

Methods of modifying through-thickness electrical conductivity of CFRP for use in structural health monitoring, and its effect on mechanical properties – A review

“…Non-destructive detection and identification of damage in CFRPs has been done using conductivity measurements [39,40,49,83,94,95], and eddy current measurements [96][97][98][99][100][101][102][103][104][105][106]. Schueler et al [40] used multiple probes and created a finite element model of a small composite to detect where and what damage was in the composite.…”

Contactless high-speed eddy current inspection of unidirectional carbon fiber reinforced polymer

“…ECT can be used in several ways to inspect carbon fibre composites [13]. It is typically used for inspecting undulations in carbon fibre reinforcement fabrics, quality control of stacking sequence, fibre orientation and curing effects [14][15][16]. Electrical properties can be characterized through various orientations with ECT techniques [17,18].…”