Detection of failures of adhesively bonded joints using the acoustic emission method

Abstract

Wooden glued constructions require touch-free monitoring of destructive processes, especially in adhesive bonds that are most exposed to failure. The objective of the investigations was to describe failure processes in the adhesive bond of wood joints, in particular to determine their initiation, propagation, and destruction. The acoustic emission (AE) method was employed as the carrier of information about changes occurring in glued joints, whereas the numerical method was applied to determine values of distribution of tangential stresses generated in adhesive bonds. The acoustic phenomena examined were described using the AE cumulative counts. The authors analysed acoustic signals generated in loaded wooden and plastic overlap samples glued together using polyethyl methacrylate glue as well as in solid samples. On the basis of the acoustic emissions obtained, it was possible to establish characteristic places and stages of escalating structural defects generated from bonds of adhesive joints. This was utilised later on, in conjunction with results of numerical calculations, to determine correlations occurring between the AE cumulative counts and generated tangential stresses. Dependencies established in this way were used to determine characteristic points during the propagation of destructive phenomena of wood adhesive joints. The results obtained proved that it was possible to predict the development of the destruction of wood adhesive joints on the basis of observations of the increasing AE cumulative counts of acoustic signals in combination with tangential stresses determined using the finite elements method.

Acoustic emission analysis of industrial plywood materials exposed to destructive tensile load

“…For plywood type 3, even though its specimens have the same physical dimension as the solid wood specimens, only half the AE activity of that for solid wood was measured. Besides the fact that glued wooden structures generally generate a lower number of AE events than solid wood (Gozdecki and Smardzewski 2005), the intrinsic pre-damage due to industrial production of plywood is also of relevance. In particular, lathe checks have already led to a prior release of the material's elastic energy during veneer processing.…”

Monitoring of Carbon Fiber-Reinforced Old Timber Beams via Strain and Multiresonant Acoustic Emission Sensors

“…The main difference between AE sensing and other non-destructive methods is the capability to inspect in real time, since continuous monitoring in situ can be carried out, and the onset and progression of damage to a structure can be assessed, even when this is not possible by means of visual inspection. Some applications of the AE method to the study of wood behavior can be found in [ 21 , 22 , 23 , 24 , 25 , 26 ], dealing with detection of failure in adhesive joints and evaluation of fractures and its propagation in wood.…”