15th International LS-DYNA Conference
The effects of Coefficient of Thermal Expansion (CTE) mismatch in multi-material adhesive joints, induced during the manufacturing process, are expected to hinder the peak performance of the adhesive in the service life of the vehicle. With a goal to estimate these effects, this paper attempts to model the curing phenomenon of an adhesive and predict its mechanical properties using MAT_277 material model available in LS-DYNA, which serves as a good starting point towards modeling the cure history dependent viscoelastic behavior of adhesives. The adhesive is used to join two substrates of dissimilar metals and tested to capture the relative displacement of substrates. The experiments are performed on a specialized setup, which is built to perform experiments on lap shear joints. The curing kinetics model is calibrated using the results obtained by advanced experimental techniques like Differential Scanning Calorimetry (DSC); the mechanical properties are modeled by Generalized Maxwell model using Dynamic Mechanical Analysis (DMA) results. The fitted parameters are fed into MAT_277 to perform simulations of the lap shear joints tests. Finally, the calibrated model is validated by comparing the relative displacement in the steel-aluminum lap shear joint on a full curing cycle, similar to automotive paint baking oven, to experimentally obtained measurements using digital image correlation (DIC). The results of this work provide insights that will help in predicting the adhesive behavior over varying temperature-time histories during the manufacturing and in the service life of the vehicle.
Agha, Akshat; Abu-Farha, Fadi; Alturk, Rakan; Welters, Tim; and Romanos, Georges, "Cure History Dependent Viscoelastic Modeling of Adhesively Bonded Joints using MAT_277 in LS-DYNA®" (2018). Publications. 98.