Internal Checking During Eucalypt Processing

Author

• Philip BlakemoreEmail author

1. 1.

Chapter

First Online: 

20 October 2010

Abstract

Collapse is a severe type of shrinkage that occurs to some extent in most species and timber types, but is particularly prevalent amongst certain species. The low to medium density Eucalypt species are particularly prone (Chafe et al. 1992). Collapse is “abnormal” in that it occurs in saturated timber above the Fibre Saturation Point (FSP) when the cell lumen is still saturated with liquid water, whereas normal shrinkage occurs below the FSP where moisture is lost from the cell walls, and the cellulose microfibrils in the walls essentially move closer together. It is collapse that causes much of the surface and internal checking problems when drying timber from many eucalypt species.

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From Present Researches to Future Developments

Author

• Voichita BucurEmail author

1. 1.

Chapter

First Online: 

20 October 2010

Abstract

Delamination phenomena in manmade composites (Tay 2003, Sridharan 2008) as well as in wood and wood-based composites have received much attention from scientists and practitioners due to serious technological implications and obvious scientific curiosity for this subject.

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Glue Line Nondestructive Assessment in Timber Laminates with an Air-Coupled Ultrasonic Technique

Author

Sergio J. SanabriaEmail author

Christian Müller

Jürg Neuenschwander

Peter Niemz

Urs Sennhauser

1. 1.
2. 2.

Chapter

First Online: 

20 October 2010

Abstract

Glued solid wood products have gained much importance during the last years, as they allow an efficient and versatile use of the renewable timber material. Current standardized methods for bonding quality assessment consist of tests of small specimens cut from the structure during production or visual in-service inspection. Ultrasonic diagnostics are traditionally based on discrete point measurements using contact techniques. Transducers are generally pressed onto the timber surface with a coupling gel, liquid, or membrane couplant. Large glue line defects in glued timber constructions have been detected with this method (Dill-Langer et al. 2005). The disadvantages are a low precision in signal level measurements, which are highly dependent on the coupling pressure, and that the coupling agent may deteriorate the object. Better repeatability and one-dimensional continuous scanning is achieved with roller transducers, which have been applied to defect inspection in hardwood lumber (Kabir et al. 2002). Non-linear effects have been used to assess delaminations between veneer lamina and particle board (Solodov et al. 2004); a welding piezoelectric stack couples high power ultrasound into the sample and its surface is scanned with a laser vibrometer.

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