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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.

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References

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

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