Abbott Aerospace – Analysis Method

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Taken from: Analysis and Design of Composite and Metallic Flight Vehicle Structures

Cored Composites

Abbott Aerospace – Analysis Method

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Taken from: Analysis and Design of Composite and Metallic Flight Vehicle Structures

Cored Composites

Composite Sandwich structures are used where additional out-of-plane stiffness is required. This out-of-plane stiffness can be required to react direct out-of plane-loads, pressure loads or used to increase buckling stability of laminate panels.

(NASA CR-1457, 1969)

Abbott Aerospace – Analysis Method

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Taken from: Analysis and Design of Composite and Metallic Flight Vehicle Structures

Cored Composites

Sandwich structures are poor in damage tolerance: The step change in stiffness at the interface between the core material and the facing laminates creates an environment where damage growth is promoted. It is common for sandwich panels which have suffered damage and subsequently subjected to cyclic loads that the facing plies over the entire cored panel area can detach from the core material.

Sandwich materials are also prone to absorb moisture if the panel is improperly sealed or suffers damage to the facing plies. The repeated cycles of freezing and thawing of water absorbed into the core can detach the facing plies from the core. The failure of the rudder on Air Transat Flight 961 in 2005 was caused by this effect.

Abbott Aerospace – Analysis Method

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Taken from: Analysis and Design of Composite and Metallic Flight Vehicle Structures

Cored Composites

The analysis of composite laminate sandwich structures has to consider different failure modes to solid laminates.

Localized Instability Modes

Ultimate Failures Precipitated by Face Wrinkling

(NASA CR-1457, 1969)

Abbott Aerospace – Analysis Method

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Taken from: Analysis and Design of Composite and Metallic Flight Vehicle Structures

Cored Composites

Note that the tension strength of a sandwich laminate is the total strength of the structural facing plies, the inclusion of a sandwich core affects the out-of-plane bending and buckling strength. The in-plane compression and shear strength of a sandwich laminate are less than for an equivalent solid laminate (taking the facing plies alone and laminating them together) because of additional failure modes that the inclusion of more material introduces

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