Thick-Walled Composite Material Pressure Hulls: Three-Dimensional Laminate Analysis Considerations

Abstract

The design of composite material pressure hulls is considered for deep submergence research vehicle applications. A thick laminate must be incorporated because of the high external hydrostatic pressure design requirements. The result is a thick-walled cylinder which by definition has a radius-to-thickness ratio less than ten. Sub- scale cylinders made of graphite/epoxy have been tested and found to fail prematurely. A failure analysis is performed to investigate the failure mechanisms. Thin laminate testing results in an ultimate compressive strength significantly higher than that obtained by sub- scale cylinder testing. Hence, a discrepancy exists between thin (2-D) and thick (3-D) lam inate testing. Through the thickness and thick laminate compression tests show that a large Poisson's ratio causes significant tensile strains through the thickness resulting from hoop and axial compressive loading. Because there is no fiber reinforcement in the through the thickness direction, these tensile strains may contribute to the cylinder failure.

Keywords

Thick-walled pressure hulls graphite/epoxy through the thickness strain compression testing.

Get full access to this article

View all access options for this article.

References

Couch, W.P. , G.D. Ward and W.F. Blumenburg . 1969. Investigation of Filament-Reinforced Plastic Deep Submergence Pressure Hulls July 1966 to March 1969, Department of the Navy, Naval Ship Research Development Center, Washington, D.C. 20007.

Garala, H.J. 1987. Structural Evaluation of Eight-Inch Diameter Graphite Composite Cylinders Subjected to Biaxial Compressive Loadings, David Taylor Naval Ship Research Development Center.

Stachiw, J.D. 1984. Graphite Reinforced Plastic Pressure Hull for the Advanced Unmanned Search System, Ocean Engineering Division, Naval Ocean Systems Center.

Hyer, M.W. 1986. Micromechanics of Compression in Unidirectional Composites , Technical Report 86-9, Mechanical Engineering Department, University of Maryland, College Park, MD 20742.

Hyer, M.W. 1987. Response of Thick Laminate Cylinders to External Hydrostatic Pressure, Technical Report No. 87-4, Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742.

Popov, E.P. 1976. Mechanics of Materials, 2nd ed., Englewood Cliffs, New Jersey: Prentice-Hall, Inc., p. 562.

Nichols, D.J. 1986. "Effect of Stress Biaxiality on the Transverse Tensile Strain-to-Failure of Composites," Composite Materials: Testing and Design (Seventh Conference), ASTM STP 893, J. M. Whitney, ed., Philadelphia, PA: American Society of Testing and Materials, pp. 109-114.