Quality Assessment of Scarf Joints Considering the Acoustic Parameters: A Nondestructive Approach

The present research studied the acoustic properties of 40 oak timber samples (Quercus castaneifolia): the acoustic coefficient (K) and acoustic conversion efficiency (ACE) in free vibration mode, using the free-free bar method with different planes of vibration, i.e., tangential (LT) and radial (LR). These acoustic parameters were considered for both primary virgin wooden beams and modified beams carrying a single scarf joint in four different bonding angles (60°, 65°, 70°, and 75°), individually glued with two different adhesives (isocyanate and polyvinyl acetate). Comparing the acoustic properties of primary solid beams with scarf jointed beams of oak wood in LT and LR planes, the steeper joint angles of 70° and 75° did not result in any serious changes with polyvinyl acetate adhesive. Scarf-jointed beams with smaller joint angles (60° and 65°) had significant effect on the acoustic properties relative to larger angles. Thus, beams having larger joint angles and beams glued using polyvinyl acetate may have enhanced acoustic properties.