The effects of porosity on the matrix-dominated mechanical properties of unidirectional carbon fiber-reinforced plastic composites were evaluated using X-ray computed tomography and mechanical testing. Carbon fiber-reinforced plastic plates of four porosity levels were manufactured by implementing different curing cycles. Porosity was detected by X-ray computed tomography tests, conducted on samples taken from the plates, and quantified by analyzing the computed tomography scans using the VGStudio Max software. Four different types of mechanical tests were conducted; namely, transverse tension, V-notched rail shear, three-point bending, and short-beam shear tests. The porosity analysis showed that with increasing the porosity volume fraction, the number of pores decreases, their volume increases while their shape changes from spherical or ellipsoidal to a needle-shape. The results from mechanical tests reveal that the presence of pores reduces all matrix-dominated material properties of the UniDirectional (UD) carbon fiber-reinforced plastic material. The reduction in strength is greater than the reduction in the elastic properties. Moreover, the reduction in the in-plane shear and interlaminar properties is greater than the tensile properties of the UD carbon fiber-reinforced plastic material. Between porosity contents of similar volume fraction, the one with the few large pores proved more severe than the one with the many small pores. The large standard deviation observed for some of the tests is attributed to the non-uniform dispersion of pores.

This work presents an overview of promising X-ray imaging techniques employed for non-destructive defectoscopy inspections of composite materials intended for the Aircraft industry. The major emphasis is placed on non-tomographic imaging techniques which do not require demanding spatial and time measurement conditions. Imaging methods for defects visualisation, delamination detection and porosity measurement of various composite materials such as carbon fibre reinforced polymers and honeycomb sendwiches are proposed. We make use of the new large area WidePix X-ray imaging camera assembled from up to 100 edgeless Medipix type detectors which is highly suitable for this type of measurements.

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