SYMPOSIA PAPER Published: 01 January 1986

Analysis of Delamination Propagation in the Composite Layer of Metal-to-Composite Stepped-Lap Joints


The initiation and propagation of delaminations in the composite layers of typical step-lap joints, with and without bondline flaws, has been investigated under typical spectrum loading. The typical bondline flaws considered are end gaps and debonds at various steps. A mathematical analysis of the stress in the joints is first carried out with the composite taken as a continuum, and the critical locations of delamination initiation are determined. The interlaminar stress analysis of critical areas in the composite is then carried out with the NASTRAN finite-element computer code. The location and magnitude of the maximum interlaminar stresses is determined. Using these interlaminar stresses in a delamination propagation model, the possibility of initiation and propagation of delamination in the composite layers is investigated. It is shown that the delaminations do not grow to failure under spectrum load in typical joints, even after four lifetimes of spectrum loading.

Author Information

Ratwani, MM
Strength and Life Assurance Research, Northrop Corporation, Hawthorne, CA
Kan, H-P
Strength and Life Assurance Research, Northrop Corporation, Hawthorne, CA
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Developed by Committee: D30
Pages: 308–321
DOI: 10.1520/STP35355S
ISBN-EB: 978-0-8031-4963-2
ISBN-13: 978-0-8031-0447-1