Paper: On finding cohesive law parameters for foam-metal interfaces

A detailed report of our work on trying to find cohesive laws for interfacial fracture is attached.  I will add the experimental data after a shorter version of this report has been published.

The reason for posting this report on iMechanica is so that people who want to replicate the tests or perform similar tests know what is involved.  As we have found out, many details and potential problems faced by an experimentalist are hard to determine from the concise papers that are typically published as journal articles.

Please let me know if you have any questions.

-- Biswajit

Title:

 On finding cohesive law parameters for foam-metal interfaces

Authors:

Benjamin Kraus and Biswajit Banerjee

Abstract:

 The availability of cohesive finite elements in commercial software has made it possible for engineers to simulate nonlinear fracture as part of the design process.  However, prediction of the behavior composite structures containing polymeric foams and, in particular, the mixed-mode failure of foam-metal interfaces continues to present a computational challenge.  This challenge stems partially from the difficulty in determining appropriate forms of cohesive laws and related parameters for foam-metal interfaces.  In this paper we characterize the cohesive behavior of the interface between a polyurethane closed-cell foam and galvanized mild steel.  Aspects of specimen preparation specific to our composite structure are described. The experimental setup consists of a unsymmetric double cantilever beam subjected to pure moments.  Digital image correlation is used to determine moment-displacement relations near the tip of an interfacial crack in the specimens.  We use a simplified approach to calculate the fracture energy from the applied moments and to extract cohesive relations from the energy-displacement data. The cohesive laws appear to be such that the normal traction is a function of not only the normal and tangential displacements but also the tangential traction. For engineering purposes we suggest bilinear cohesive relations be used for the interface with peak normal and tangential tractions of 0.2 MPa and 0.9 MPa, respectively.  Normal and tangential separations at loss of cohesion are approximately 1.7 mm and 0.2 mm.  Peak tractions are achieved at normal and tangential separations of 0.6 mm and 0.05 mm, respectively.

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Please used the following BibTeX citation to cite this paper:

 @MISC{Kraus14,
    AUTHOR       = "Kraus, B. and Banerjee, B.",
    YEAR         = "2014",
    TITLE        = "On finding cohesive law parameters for foam-metal interfaces",
    PUBLISHER    = "iMechanica",
    PAGES        = "1--76",
    howpublished = "node/16101",
    }
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