Finite element stress analysis of idealized composite damage zones

This study was concerned with linear and nonlinear stress and failure analysis of an idealized damage zone in a laminated composite under compressive loading. The following conclusions can be made from results of the analysis. 1. A boundary layer exists around the damage zone; it is similar to the boundary layer along the free edges. 2. Interlaminar stresses in the boundary layer around the damage zone are similar to those produced at the free edge. 3. The interlaminar stresses around the damage zone may be as large or larger than those at the free edge depending upon the fiber orientations and stacking sequence. 4. The boundary layer associated with the damage zone extends as far or farther into the interior of the laminate as does the free edge effect, depending on fiber orientation and stacking sequence. 5. Only laminated materials with more than one fiber orientation are affected by the damage zone. 6. Lamination theory is valid in interior regions away from free edges and the damage zone. 7. The presence of a damaged zone induces interlaminar stresses in an interior region away from free edges and the damage zone. 8. Due to interlaminar stresses produced in an interior region, failure, defined by a Tsai-Wu failure criterion, may initiate in the interior away from free edges and the damage zone. 9. The cutout extending down to a ±45 interface may produce large stress concentrations near the edge of the damage zone, depending upon the fiber orientations and stacking sequence. 10. Elastic results adequately predict where failure initiates for the laminate considered. 11. A damaged [90/±45/0]_s laminate fails at approximately 60 percent of the load carried by an undamaged laminate. 12. For a [90/±45/0]_s laminate, initial failure occurs at the free edge in the 0° layer. Subsequent failure in the interior of the 0° layer as well as at the free and cutout edges of the other layers leads to total failure. This investigation indicates that future areas of study should include: 1. Linear and nonlinear analysis of hygrothermal effects in laminates with idealized damage zones. 2. A three layer damage zone (cutout) in an eight layer laminate. 3. The effects of varying geometric parameters such as cutout width and layer thickness. 4. More detailed nonlinear analysts. 5. An improved method for modeling failure and unloading of an element. 6. Experimental study of specimens with idealized damage Zones to compare with theoretical analysis. 7. Analysis capability for bending of unsymmetric laminates.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Engineering Mechanics

Department dc:contributor.department

Engineering Mechanics

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1977

Author dc:creator

• O'Brien, David A.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-06122010-020327

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/43252