Porosity Determination in CFRP by means of X-ray Computed Tomography Methods

Plank, Bernhard; University of Applied Sciences Upper Austria; Austria

Plank, B.; University of Applied Sciences Upper Austria; Austria
Gusenbauer, C.; University of Applied Sciences Upper Austria ; Austria
Senck, S.; University of Applied Sciences Upper Austria; Austria
Hoeller, H.; FACC Operations GmbH; Austria
Kastner, J.; University of Applied Sciences Upper Austria ; Austria

ID: ECNDT-0231-2018
Download: PDF
Session: CT-Applications 2
Room: G3
Date: 2018-06-13
Time: 11:50 - 12:10

Especially in aeronautic and space industry it is important to produce carbon fibre-reinforced polymers (CFRP) with very low porosity since there is a direct relation between porosity and mechanical properties, such as shear strength. Typical acceptable porosity values are in the range of < 2.5 vol.%. The most common non-destructive method for measuring the porosity is ultrasonic testing (UT) assuming there is a linear correlation between ultrasonic attenuation and porosity. However, the ultrasonic attenuation coefficient depends not only on the porosity, but also on the shape and distribution of the pores, the presence of other material inhomogeneity’s and the individual material system. This can lead to significant errors in the determination of the porosity. Acid digestion and materialography are mainly used as reference method, but both methods are destructive, time-consuming and inaccurate. This paper deals with the application of X-ray computed tomography (XCT) methods as reference for quantitative evaluation and characterization of porosity in carbon fibre-reinforced composites. The degree of accuracy strongly depends on several material and XCT parameters: • Material parameters: woven fabric or unidirectional material, additional glass fibres or copper wires for lightning protection, higher dense epoxy used for adhesive bonding, etc. • XCT parameters: resolution and voxel size (VS), used XCT device and modality (e.g.: cone beam XCT vs. Talbot Lau grating interferometer XCT), threshold method, etc. In this contribution several mentioned parameters influencing the quantitative evaluation of porosity in CFRP are discussed and different types of CFRP with porosity are presented. Porosity values gained with XCT methods are compared with UT, acid digestion or materialography.