Abstract: A coating for metal sheets used in fabricating honeycomb structures. The coating includes a first layer located on the surface of the metal sheet. The first layer includes hydrated alumina dispersed in a binder. The coating may further include a second layer located on top of the first layer. The second layer includes a polymer sealant. The first and second layer form a coating which is corrosion resistant and bonds well to the node adhesives used in forming honeycomb structures.

Abstract: An improved resin for use in making honeycomb sandwich panels. The improvement involves modifying a phenolic resin so that the amount of smoke and heat generated during combustion is reduced. The reduction in smoke and heat generation is achieved by reducing the amount of phenol used to form the phenolic resin. The phenol is replaced by low-smoke producing sulfone compounds such as 4,4′-bisphenol-S, 3,3′-bisphenol-S, biphenol and bisphenol ethers which reduce the number of smoke producing methylene or methylene ether linkages present in the cured phenolic resin. The low-smoke producing resin may be used as a dip resin for coating the honeycomb or as the matrix resin for the core and face sheets of the sandwich panel.

Abstract: A coating for metal sheets used in fabricating honeycomb structures. The coating includes a first layer located on the surface of the metal sheet. The first layer includes hydrated alumina dispersed in a binder. The coating may further include a second layer located on top of the first layer. The second layer includes a polymer sealant. The first and second layer form a coating which is corrosion resistant and bonds well to the node adhesives used in forming honeycomb structures.

Abstract: An improved resin for use in making honeycomb sandwich panels. The improvement involves modifying a phenolic resin so that the amount of smoke and heat generated during combustion is reduced. The reduction in smoke and heat generation is achieved by reducing the amount of phenol used to form the phenolic resin. The phenol is replaced by low-smoke producing sulfone compounds such as 4,4′-bisphenol-S, 3,3′-bisphenol-S, biphenol and bisphenol ethers which reduce the number of smoke producing methylene or methylene ether linkages present in the cured phenolic resin. The low-smoke producing resin may be used as a dip resin for coating the honeycomb or as the matrix resin for the core and face sheets of the sandwich panel.

Abstract: A solventless node adhesive for use in bonding honeycomb layers together. The node adhesive includes thermoset resin and thermoplastic particles dispersed in the adhesive. The node adhesive is applied to the honeycomb node lines while the thermoplastic particles remain dispersed in the adhesive. The amount of thermoplastic particles in the node adhesive is selected to keep the viscosity of the adhesive between 30 and 150 poise at room temperature. The node adhesive may be applied to the honeycomb nodes using conventional application procedures. The thermoplastic particles are dissolved during heat curing of the thermoset resin to form a thermoplastic toughened node adhesive.

Abstract: Resins which are a combination of phenolic and polyamide polymers are used as dipping resins to coat composite honeycomb structures. The phenolic/polyamide dipping resins increase the heat formability of composite honeycomb structures. The dip resin forms a coating on the honeycomb which includes from 30 to 95 weight percent phenolic resin and 5 to 30 weight percent polyamide resin. The dip resin is especially useful for coating composite honeycomb cores made from graphite or glass fibers impregnated with flexible phenolic resins.

Abstract: A solution of phenolic and polyamide polymers is used as a dipping resin to coat composite honeycomb structures. The phenolic/polyamide dipping resin increases the heat formability and strength of composite honeycomb structures. The coating formed by the resin includes from 30 to 95 weight percent phenolic resin and 5 to 30 weight percent polyamide resin.

Abstract: High strength foam-filled materials and methods for their production are disclosed. The high strength materials include cellular structures comprising a plurality of open-ended cells containing polycyanurate foam. The polycyanurate foam-filled cellular structures have synergistically high mechanical properties and improved resistance to moisture. When cyanate ester foamable precursors in the form of tough films are foamed to fill honeycomb cells, the resulting foam-filled honeycomb has uniformly fine foam cell structure and improved bonding between the foam and the honeycomb.

Abstract: Foamable resin compositions of cyanate esters and thermoplastic resins are disclosed.