Optimal sandwich core structures and forming tools for the mass production of sandwich structures

Abstract

A sandwich structure is provided that includes a corrugated layer with at least one core layer (structure) made of a periodic array of adjacent truncated upward facing peaks and truncated downward facing valleys. Each truncated peak has a bonding land of an area A1. Each truncated valley has a bonding land of an area A2. A ratio of A1 / A2 is less than 2. A distance D is between neighboring peaks, and a distance D is also between neighboring valleys. The corrugated layer is made from an initially flat sheet thickness of t. A first sheet layer is physically coupled to bonding lands of the truncated peaks. A second sheet layer is physically coupled to bonding lands of the truncated valleys.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of U.S. patent application Ser. No. 13 / 859,474, filed on Apr. 9, 2013, which is a continuation-in-part of U.S. patent application Ser. No. 13 / 419,613 filed on Mar. 14, 2012, both of which are fully incorporated by reference herein.FIELD OF THE INVENTION[0002]The presented invention relates generally to structural / multifunctional material designs and methods for their manufacturing, and more specifically to sandwich core structures that are made from initially flat sheets and bonding techniques to form cellular solids with periodic microstructures.BACKGROUND OF THE INVENTION[0003]Cellular solids are highly porous space filling materials with periodic or random microstructures. The effective properties of cellular solids are sensitive to the geometry of the underlying microstructures and the properties of the basis material from which these microstructures are made. In man-made cellular solids, the control...

AI Technical Summary

Benefits of technology

The present invention provides an optimized sandwich core structure for cost-effective mass production. The corrugated core structure has bounds for specific dimensions of the forming tool geometry for optimal mechanical performance. Further, the invention provides a uni-directionally corrugated core structure with periodically enlarged bonding lands for enhanced shear force transmission between the core structure and the face sheets, as well as for enhanced shear force transmission between two contacting core layers when using multi-core layer assemblies. The invention provides a solution for applications where both costs and weight-specific mechanical performance are equally important.

Problems solved by technology

In man-made cellular solids, the control of the microstructural geometry and the basis material properties is one of the key challenges in manufacturing.

Foamed cellular solids typically feature a random microstructure of foam cells which is usually characterized through poor weight specific mechanical performance.

However, it appears to be impossible to manufacture metallic honeycombs in a cost-effective mass production process.

However, their weight specific mechanical performance is usually inferior to that of honeycombs.

In particular, when used in metal sandwich construction, the bonding land between the core structure and the face sheets is often too small to transmit the full shear force through an adhesive bond.

In other words, delamination between the core structure and the face sheets is often the critical failure mode.

In addition, the bonding land between a uni-directionally corrugated core structure and the face sheets is rather small and not well defined.

However, the applicability of Hale's invention seems to be limited to highly formable materials such as thermoplastics.

When using conventional sheet metal, premature fracture typically limits the making of anticlastic structures (FIG. 1).

The procedures are thus limited to the production of small panels.

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