Detection of glue deficiency in laminated wood with pulse thermography |
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| Authors: | Henrik Berglind Alexander Dillenz |
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| Institution: | 1.Tr?tek – The Swedish Institute for Wood Technology Research, Skeria 2, S-931 77 Skellefte?, Sweden
Tel. +46-910-58-5208; Fax +46-910-58-5265
e-mail: henrik.berglind@tratek.se,SE;2.IKP – Institute for Polymer Testing and Polymer Science, Universit?t Stuttgart, D-70569 Stuttgart, Germany,DE |
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| Abstract: | Adhesion problems sometimes occur during the production of laminated wood products. To minimize such quality problems, there
is a need for a nondestructive test that can provide continuous control of the process and the product. This study presents
results from measurements performed to evaluate the potential of pulse thermography as a method to detect glue deficiency
in laminated wood. Defect depth, defect size, and degree of glue deficiency have been varied. The surface layer was made of
merbau (Intsia bijuga) and the substrate of Scots pine (Pinus silvestris). The results showed that pulse thermography is a promising tool for detecting glue deficiency underneath the thin laminated
wood surface layers, mainly because of the short inspection time. Lack of glue with a minimum thermal defect size of 3 was
detectable (thermal defect size is defined as the quotient of defect size and defect depth). The penetration depth was 1.0 mm
and the highest contrast, 0.62°C, was achieved for one of the largest defects (24 mm) below the thinnest (0.5 mm) surface
layer after 1 second. Starved glue joints showed about half the contrast compared to areas with total lack of glue.
Received: April 24, 2002 / Accepted: July 26, 2002
Acknowledgments We gratefully acknowledge the support of this work from the Knowledge Foundation and The Swedish Wood Association. |
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| Keywords: | Pulse thermography Laminated wood Glue line Adhesive bonding Delamination |
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