Characterisation on the influence of curing history on the mechanical performance of adhesively bonded corrugated sandwich structures

This paper investigates the effect of curing history on the strength behaviour and cohesive properties of adhesively bonded corrugated sandwich structures with a structural adhesive. Three-point bending tests under both longitudinal and transverse loading directions were taken into account. The selected curing histories of adhesively bonded corrugated sandwich structures were: a) 2 h at temperature of 40 degrees C; b) 2 h at 40 degrees C and then 2 h at 60 degrees C; c) 2 h at 40 degrees C, then 2 h at 60 degrees C and 1 h at 80 degrees C. To predict adhesive joint mechanical behaviour with different curing conditions, bulk tensile, Double Cantilever Beam, and End-Notched Flexure tests were conducted for material characterisation and verification of the subsequent developed numerical analysis. The glass transition temperatures (T-g) of the adhesive with different curing histories were determined using differential scanning method. Crack propagation and stress distribution in the adhesive layer was simulated using the bilinear traction-separation law of Cohesive Zone Model. The predicted critical ultimate loads and the corresponding failure modes were proved to be in good correlation with the experimental observation. The presented study revealed that gradual step-wise increasing in curing temperature and duration can effectively strengthen the mechanical performance and fracture resistance of adhesively bonded corrugated sandwich structures.