Mode I traction-separation measured using rigid double cantilever beam applied to structural adhesive

ABSTRACT

Adhesive joining facilitates the development of multi-material vehicle structures; however, widespread adoption requires material properties to characterize adhesive joints for implementation in finite element (FE) models. Specifically, modeling adhesive joints using the cohesive zone method requires measuring the Mode I traction-separation response, which currently requires multiple tests. To address this need, a new method to determine the Mode I response was developed using the Rigid Double Cantilever Beam (RDCB) test, where the steel adherend geometry was designed to ensure high stiffness compared to structural epoxy adhesives. The samples were tested in tension with displacements measured from high-resolution imaging of the test. A new analysis method was developed with resulting Mode I traction-separation response within the expected range for this structural adhesive. The analysis was verified using a FE model of the test and compared to Tapered Double Cantilever Beam test data. Importantly, the predicted force-displacement response from the FE model, using the measured traction-separation curve, compared well to the measured force-displacement data. The proposed RDCB test demonstrated the ability to determine the Mode I response of a toughened structural adhesive using a single test, the results of which can then be readily implemented into FE simulations.

KEYWORDS:

• Cohesive zone modeling
• Mode I
• structural adhesive
• traction-separation curve

Nomenclature

b = length of the bond line

B = sample thickness

E_adherend = Young’s modulus of adherend

F = applied force on loading pins

L = distance from the edge of the sample to the point of loading

S_init = initial slope of traction-separation response

t(x), t(δ) = arbitrary traction–displacement functions

t_c = peak compression traction

v = length on axis perpendicular to bond line with origin at center of bond line

x = length on axis parallel to bond line with origin at μ = 0

α = rigidity ratio

δ = crack opening (separation)

δ_c = closing distance at the edge of the sample due to the compression of the bond line

Δ = load point opening displacement

υ_adherend = Poisson’s ratio of adherend

μ = distance from edge of sample to transition between tensile and compressive loading of bond line

Acknowledgements

The authors would like to express their thanks to Honda Research and Development Americas, 3M Canada Company, ArcelorMittal, Compute Canada and the Natural Sciences and Engineering Research Council of Canada (NSERC) for their support of this research.

Additional information

Funding

This work was supported by the Natural Sciences and Engineering Research Council of Canada; Arcelor Mittal Dofasco; Honda R&D Americas; 3M Canada.