Assessment of glued timber integrity by limited-angle microfocus X-ray computed tomography

Abstract

Glued timber products have an extensive range of applications in construction. In this work a Microfocus X-ray Computed Tomography method was developed to inspect gluing defects in timber samples and was applied successfully on experimental data. The bonding plane was segmented into glued and non-glued regions and imaged with 5 mm resolution. Moreover, the gap topology between timber lamellas was precisely characterised. A limited-angle reconstruction with anisotropic frame binning together with a specific glue line readout method efficiently filters out undesired wood structure highlighting the information of the adhesive joint. This method imposes limitations on the size of the specimen in only one dimension. The presence and absence of glue could be detected for glue line thicknesses over 50 μm and air gaps larger than 150 μm could be characterised. Several information reduction approaches were combined in the reconstruction process to implement the assessment of a 100 × 100 mm 2 bonding plane in less than 40 s. Detektion von Fehlverklebungen in Holzbauteilen mittels Mikrofokus Röntgen-ComputertomographieZusammenfassung Holzverklebungen gewinnen zunehmend an Bedeutung. Im Rahmen dieser Arbeit wurde ein Mikrofokus Röntgen-Computertomographie Messverfahren

Delamination detection in a 90-year-old glulam block with scanning dry point-contact ultrasound

“…X-ray computed tomography (CT) was applied on solid wood with cracking (Niemz et al 1997), and it was possible differentiating between glued and delaminated regions in glued structures by CT (Hu and Gagnon 2007). Limited-angle microfocus CT is able to detect air gaps larger than 150 μm in the joint of 100 mm broad spruce lamellas (Sanabria et al 2011d). …”

Air-coupled ultrasound inspection of glued laminated timber

“…Infrared thermography is limited to inspection of thin veneer (Berglind and Dillenz 2003). Computed tomography (CT) methods based on non-refracting radiation (X-ray, neutrons) can detect the absence of adhesive in wood composites (Hu and Gagnon 2007;Osterloh et al 2008;Sanabria et al 2010a). However, the hazardous nature of these methods still constrains their application on site.…”

Air-coupled ultrasound wave propagation in glued laminated timber structures applied to bonding quality assessment

“…Fig. 4c shows an amplitude image obtained from the ultrasound dataset with a tracking algorithm, which exploited the spatial continuity of ACU datasets to follow the amplitude of the first incoming oscillation [8], the latter corresponding to the fastest (denoted as QPx) mode. The amplitude variability pattern masks the defect position (non-glued area of 30x60 mm 2 ).…”

“…Infrared thermography detects changes in thermal conductivity in the presence of delamination [6]; however, it is limited to thin veneer inspection. X-ray and neutron computed tomography can segment the presence or absence of adhesive in wood composites [7,8]; however, their hazardous nature constrains their use on site. Ultrasonics are highly sensitivity to This work was supported by the Swiss National Science Foundation under contract 200021-115920. delaminated interfaces, and portable to the construction.…”