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TECHNOLOGIES FOR REDUCING CORE CRUSH

IP.com Disclosure Number: IPCOM000006700D
Publication Date: 2002-Jan-23
Document File: 3 page(s) / 40K

Publishing Venue

The IP.com Prior Art Database

Abstract

Partial collapse of a honeycomb core during curing of a composite is known in the industry as "core crush" and is a particularly common reason for rejection of cured panels. Substantial effort and research extending over many years have been directed to eliminating the core crush problem. Some of the better known techniques are presented.

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ABSTRACT

TECHNOLOGIES FOR REDUCING CORE CRUSH

Partial collapse of a honeycomb core during curing of a composite is known in the industry as "core crush" and is a particularly common reason for rejection of cured panels. Substantial effort and research extending over many years have been directed to eliminating the core crush problem.  Some of the better known techniques are presented.

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TECHNOLOGIES FOR REDUCING CORE CRUSH

Honeycomb core composite sandwich structures find widespread use in the aerospace industry as panel components in various aerospace structures.  The honeycomb core composites are formed from a lay-up of prepreg skin plies encompassing a honeycomb core, the latter typically having beveled edges.

The high strength properties of the fibers and the resin, in combination with the strength properties of the honeycomb core component, impart high strength-to-weight, and high stiffness-to-weight ratios to the final composite structure.

Partial collapse of the honeycomb core during curing of the composite, known in the industry as the "core crush", is a particularly common reason for rejection of cured panels.  Core crush is typically observed in the beveled edge or chamfer region of the honeycomb structural part after the prepreg is cured.

Substantial effort and research extending over many years have been directed to eliminating the core crush problem.  For example, it was discovered that one could adhere the plies effectively to one another to  increase resistance of shera forces on the prepreg by applying a low temperature curing film adhesive between the tie down plies just outside the net trim line of the part.  In the autoclave, this film adhesive melts and cures at a lower temperature than the resin in the laminates so that it bonds the tie down plies together prior to increasing the autoclave pressure to the higher temperature where the primary laminate resin flows and cures.

A method for minimizing core crush is the use of at least one stiffness-treated prepreg ply in the construction of a honeycomb sandwich structure.

The method of utilizing stiffness-treated fabrics is to use a treated fabric having an ASTM stiffness value greater than the ASTM stiffness value of an untreated fabric and then, by combining those stiffened fibers with a polymeric material.

Another method for attaining good core crush performanc...