Experimental Characterization and Modified Constitutive Modeling of the Strain Rate Dependent Compressive Behavior of Adhesives

Abstract

Predicting the impact performance of adhesively bonded structures requires the accurate characterization and constitutive formulation of the compressive behavior of the adhesive at dynamic strain rates. In this work, the stress–strain curves of Sikaflex adhesives are measured in uniaxial compression tests at quasi‐static and dynamic strain rates. The split‐Hopkinson pressure bar technique is modified with the hollow output bar to effectively characterize the dynamic response of the adhesive. It is found that the Sikaflex adhesive is incompressible and hyperelastic; the compressive behavior is significantly influenced by the strain rate. The strain rate sensitivity is not constant but varies as a function of the strain and the strain rate. The strain rate effect on compressive behavior is quantified and incorporated into the phenomenological hyperelastic constitutive model based on strain energy density. The modified constitutive equation accurately represents the strain rate dependent compressive behavior of Sikaflex adhesives.

Visco‐elasto‐plastic constitutive model of adhesives under uniaxial compression in a range of strain rates

“…The specimen volume ( V ) was calculated from the recorded 2D image with the assumption of axisymmetric longitudinal deformation, and then normalized by the original volume ( V 0 ). The procedure details can be found in the authors' previous work . As shown in Figure , the specimen volume change is less than 1%, implying that the adhesive material is incompressible.…”

“…The dynamic strain rate is defined as the slope of the linear portion. The SHPB system, analysis of recorded wave signals and verification of stress uniformity have been detailed in the authors' previous studies on several different materials …”

“…A bilinear relation was observed between the stress and the logarithm of strain rate for a variety of polymers . The viscous nature of polymers or elastomers causes the apparent rate sensitivity (e.g., in modulus and yield stress) even in the low loading rate range . The reliable measurement of dynamic behavior of polymers offers the physical insight in the development of a constitutive model.…”

“…The reliable measurement of dynamic behavior of polymers offers the physical insight in the development of a constitutive model. However, it is still challenging to experimentally measure the high rate response of a soft polymeric material …”

“…Various constitutive models have been developed to represent the mechanical behavior of polymeric materials on the basis of experimental observations . Phenomenological models using empirical equations are widely accepted as they are practically simple and can well describe the nonlinear deformation behavior . An elasto‐viscoplastic constitutive formula coupled with micromechanics and statistical thermodynamics has been proposed to simulate the response of toughened polymeric materials, such as toughened polycarbonate in both microscopic and macroscopic scales .…”