RESEARCH PAPERS: Special Issue on Time-Dependent Behaviors of Polymer Matrix Composites and Polymers

Cohesive Layer Modeling of Time-Dependent Debond Growth in Aggressive Environments

[+] Author and Article Information
Samit Roy

Department of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078-5012rsamit@ceat.okstate.edu

Yong Wang

Department of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078-5012

Soojae Park, Kenneth M. Liechti

Engineering Mechanics Department, University of Texas-Austin, Austin, TX

J. Eng. Mater. Technol 128(1), 11-17 (Apr 26, 2005) (7 pages) doi:10.1115/1.2127959 History: Received August 11, 2004; Revised April 26, 2005

The objective of this paper is to model the synergistic bond-degradation mechanisms that may occur at the interface between a fiber-reinforced polymer (FRP) that is adhesively bonded to a substrate and subjected to elevated temperature and humidity. For this purpose, a two-dimensional cohesive-layer constitutive model with a prescribed traction-separation law is constructed from fundamental principles of continuum mechanics and thermodynamics, taking into account strain-dependent, non-Fickian hygrothermal effects as well as diffusion-induced degradation in the cohesive layer. In the interest of solution tractability, a simplified approach is employed where the rate-dependent behavior in the cohesive layer is implemented through the characterization of rate dependence of the maximum stresses and maximum strains in the cohesive layer, rather than through the use of convolution integrals in the free-energy definition. The remainder of the polymeric adhesive outside the cohesive layer is modeled as a nonlinear viscoelastic continuum with time-dependent constitutive behavior. The influence of temperature and moisture concentration on the work-of-separation and on crack growth is derived from first principles. The model is implemented in a test-bed finite element code. Results predicted by the computational model are benchmarked through comparison to experimental data from mixed-mode fracture experiments performed using a moving wedge test.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Double cantilever beam (DCB) with a cohesive layer

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Figure 2

Cubic stress-strain traction-separation law for cohesive layer

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Figure 3

Specimen of moving wedge test

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Figure 4

Debond length versus time (test results and FEM prediction)

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Figure 5

Vertical reaction force versus time (test results and FEM prediction)

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Figure 6

Stress-strain relation of epoxy under different strain rates

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Figure 7

Fracture energy 2Γ versus debond speed

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Figure 8

FEM mesh and contour for J integral




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