Volume 2, Issue 8 (September 2005)
Method for Quantifying Percentage Wood Failure in Block-Shear Specimens by a Laser Scanning Profilometer
A new method for quantifying percentage wood failure of an adhesively bonded block-shear specimen has been developed. This method incorporates a laser displacement gage with an automated two-axis positioning system that functions as a highly sensitive profilometer. The failed specimen is continuously scanned across its width to obtain a surface failure profile. The laser is then moved incrementally along the length of the specimen and repeatedly scanned to obtain a three-dimensional digital profile of the surface. This digital profile can then be reconstructed and analyzed with appropriate software. Special algorithms are used to quantify percentage wood failure and degree of wood failure (depth of wood failure) and to recognize various surface anomalies, such as bondline voids. This paper presents exploratory data on several different types of wood failures and correlates these measurements to the visual inspections of skilled evaluators. The device is very sensitive to most observed failures, particularly those with deep wood failure. However, shallow failures close to the bondline can be problematic. The algorithms allow a “roughness” tolerance to be specified to characterize these surfaces. This new method will be useful for automating measurement of wood failure in block-shear specimens with good precision and repeatability.