The effects of bridging in a 3D composite on buckling, postbuckling and growth of delamination |
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Authors: | Y-T Hu Y-Y Huang S-P Li W-F Zhong |
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Institution: | (1) Dept. of Mechanics, Huazhong University of Science and Technology, Wuhan 430074, P.R. China, CN |
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Abstract: | Summary Buckling and postbuckling solutions to circular delamination constrained by transversal restoring forces, which occur extensively
in stitched or woven composites with three-dimensional (3D) reinforcement, are obtained by using von Karman's geometrically
nonlinear thin plate theory by means of Taylor's series expansion. The through-thickness tows are assumed to provide continuous
and linear restoring tractions, opposing the deflection of the annular delaminated region adjacent to a penny-shaped crack.
When the end of the delaminated layer is clamped, and the deflection is permitted in the positive direction of the z-axis only, there exists a characteristic delamination radius a
* for initial buckling. In the case that the initial delamination radius a
0 exceeds a
*, it will consist of waves whose sizes decrease gradually, as they are apart from the delamination center with larger distances,
and will usually not span the whole crack region. Therefore, buckling profiles can be divided into two types: (1) lacking
contact phenomena between the delaminated layer and the base plate; (2) having contact surfaces inside the delamination region.
In this paper, growth laws of buckling, postbuckling and growth of delamination at lacking contact surface are discussed.
The corresponding stability of the delamination growth under fixed boundary load is studied, and the dependence of stable
scope upon the fracture toughness of the composite and the elastic constant of bridging fiber is summarized. It follows from
the analysis that bridging can increase the load-bearing capacity of composite structure, improve its mechanical performances
and restrain the growth of delamination.
Received 23 November 1998; accepted for publication on 13 January 1999 |
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Keywords: | Delamination buckling postbuckling composite fracture criterion |
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