2024 Volume 60 Issue 2 Pages 50-56
The fracture and fatigue lifetime of adhesive bonded structures are predominantly impacted by crack initiation and propagation of adhesive bonded joints. This commentary deals with fatigue crack growth behaviors of adhesive bonded joints. Fatigue tests were conducted using double cantilever beam specimens to measure the fatigue crack growth properties of commercially available and developed adhesives under mode-I loading on steel adherends. The displacement-controlled fatigue cyclic with constant a max/min load ratio of 0.1 or 0.5 was used to evaluate the threshold fatigue crack growth properties using adhesive thicknesses of 0.3 and 3.0 mm. The results show that the equivalent energy release rate was an effective parameter to evaluate the effect of different load ratios and adhesive type and thickness on the fatigue crack growth properties. The fatigue crack growth properties of adhesive bonded joints for each adhesive were clarified. The threshold energy release rate decreased with the adhesive thickness and there was a trend for each adhesive that the higher fracture toughness showed the higher threshold energy release rate. The slopes defined by the Parisʼ law exhibited similar values for each adhesive with different adhesive thicknesses and there was a trend for each adhesive that the lower slope showed the higher threshold energy release rate ratio. Through the experimental procedure, results, and discussion described in the commentary, the evaluation method of fatigue crack growth properties of adhesive bonded joints and key considerations were outlined.
