Automated multisource electromagnetic inspection of fibre-cement boards

This article proposes selected non-destructive testing methods for evaluating fibre-cement boards as to the potential occurrence of heterogeneities or defects in them. First the most common material defects in such boards are described. Then selected methods (radiography and THz imaging) exploiting high frequency electromagnetic waves are introduced. Measurements of defective and flawless boards were carried out using the methods. Selected results of the measurements are presented. The preliminary tests have proved the proposed method to be useful for testing fibre cement boards. It is demonstrated that radiographic inspection enables one to assess the homogeneity and density of fibre-cement boards and can also be used to detect cracks. In the case of delamination detection and the identification of layer thickness, the terahertz time domain system is more useful.