Role of delamination and interlaminar fatigue in the failure of laminates with ply dropoffs

Analytical and experimental investigations were conducted on laminates with ply dropoffs to better understand the interlaminar stress field and delamination/damage characteristics in such laminates, as well as the relationship between the two based on the strength of materials approach. To gain key insights into the mechanisms and structural parameters that cause interlaminar stresses, analytical models for laminates with simple ply dropoff configurations were developed based on a systematic and hierarchical approach. Mathematically, these individual models are formulated using the stress function method in which the form of the admissible stress field is assumed a priori based on the stress field from the classical laminated plate theory and other functional constraints of the problem. The results are validated via comparisons with numerical solutions from previous investigations and as performed in the current work. Various structural parameters such as the taper angle and the location of the terminated plies are found to affect the interlaminar stress distribution. Careful consideration of the characteristics and trends of the interlaminar stresses in such laminates reveals that two fundamental mechanisms give rise to interlaminar stresses: the termination effect, that is caused by the load transfer from the terminated ply group to the continuous plies; and the offset effect, that is caused by the redistribution of the load from the undropped region to the dropped region in the outer continuous plies through an offset in the through-thickness direction. These mechanisms, the factors that affect them, and their utility are described and discussed in detail.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2002

Author dc:creator

• Shim, Dong Jin, 1972-

Advisor dc:contributor.advisor

• Paul A. Lagace.

• Aeronautics and Astronautics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/29245

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29245