HexWeb Honeycomb Attributes and Properties

1 HexWeb HoneycombAttributes andPropertiesA comprehensiveguide to standardHexcel honeycombmaterials, configurations, and mechanicalproperties99 HXDH1679 Rv. HW HC Guide 11/24/99 2:37 PM Page 2 ContentsIntroduction ..2 How Honeycomb Is Manufactured .. 3 Honeycomb Cell Configurations .. 4 Honeycomb Materials .. 6 Aluminum .. 6 Fiberglass .. 7 Aramid Fiber .. 7 Nomex ..7 Kevlar ..7 KOREX ..8 Special Honeycomb .. 8 Carbon ..8 Polyurethane ..8 Specifying Honeycomb .. 9 Guide to Determining Which Type of Honeycomb to Specify .. 9 Most Important Attributes of Each Honeycomb Material .. 9 Mechanical Properties and Test Methods ..10 Density and Thickness Measurements .. 10 Compressive Properties .. 10 Crush Strength .. 10L and W Shear Properties .. 11 Additional Mechanical Properties .. 12 Classification of Mechanical Properties .

2 12 Correlation of Shear Strength Data ..13 Effect of Core Thickness on Plate Shear Strength .. 13 Correlation of Flexural Shear Strength Data .. 14 Mechanical Property Tables ..155052 Alloy Hexagonal Aluminum Honeycomb Specification Grade .. 165056 Alloy Hexagonal Aluminum Honeycomb Specification Grade .. 17 Aluminum Commercial Grade (ACG ) .. 175052 Alloy RigicellTMAluminum Corrugated Honeycomb .. 185052 and 5056 Alloy Aluminum Flex-Core Specification Grade .. 18 HRP Fiberglass Reinforced Phenolic Honeycomb .. 19 HFT Fiberglass Reinforced Phenolic Honeycomb .. 19 HRH -327 Fiberglass Reinforced Polyimide Honeycomb .. 20 HRH -10 Aramid Fiber/Phenolic Resin Honeycomb .. 21 HRH -310 Aramid Fiber/Polyimide Resin Honeycomb .. 21 HRH -78 Nomex Commercial Grade Aramid Fiber/Phenolic Resin Honeycomb .. 22 HRH -49 Kevlar 49 Honeycomb .

3 22 KOREX Aramid Fiber/Phenolic Resin Honeycomb .. 22 TPU Thermoplastic Polyurethane Honeycomb .. 22 HexWeb Honeycomb Attributes and Properties99 HXDH1679 Rv. HW HC Guide 11/24/99 2:37 PM Page 3 CFC, CR-PAA, Double-Flex, HexWeb , Micro-Cell, OX-Core, Rigicell, and TPU are trademarks of Hexcel Corporation, Pleasanton, California. ACG,Acousti-Core, CECORE, CR III, CROSS-CORE, Fibertruss, Flex-Core, HFT, HOBE, HRH, HRP, Tube-Core, Hexcel, and the Hexcel logo are registered trademarks of Hexcel Corporation, Pleasanton, California. Kevlar, KOREX, and Nomex and are registered trademarks of DuPont de Nemours,Wilmington, of Typical Mechanical Properties and Other Design Considerations .. 23 Additional Properties of Honeycomb .. 28 Acoustical ..28 Air/Fluid Directionalization ..28 Pressure Drop Across Honeycomb .

4 28 Bending of Honeycomb ..29 Coefficient of Thermal Expansion ..29 Dielectric ..30 Energy Absorption ..31 Moisture Absorption ..32 Radio Frequency Shielding ..32 Thermal Conductivity ..32 Comparison and Benefits of Honeycomb Versus Alternative Core Materials ..34 Applications .. 35 Hexcel Honeycomb Technical Literature Index .. 3699 HXDH1679 Rv. HW HC Guide 11/24/99 2:37 PM Page 4 HexWeb Honeycomb Attributes and Properties2 IntroductionHexcel has produced more than 700 varieties of Honeycomb over the past 50 , HexWeb Honeycomb is available in a wide range of materials and cell configurations, and additional products are continually developedin response to new uses for Honeycomb sandwich brochure lists the materials, configurations, and mechanical Properties of Hexcel s standard Honeycomb as a guide to selecting Honeycomb core best suited for particular Stiffness1007007 times more rigid370037 times more rigid!

5 Solid MetalSheetSandwichConstructionThickerSan dwichRelative times as times as strong!Relative Weight1001033% increase in weight1066% increase in weightA striking example of how Honeycomb stiffens a structure without materially increasing its Rv. HW HC Guide 11/24/99 2:37 PM Page 5 How Honeycomb Is ManufacturedHoneycomb is made primarily by the expansion corrugated process is most common for highdensity Honeycomb Process of Honeycomb ManufactureLLLTWebTWW1 Corrugated BlockCorrugated RollsRollCorrugated SheetCorrugated SheetCorrugated ProcessThe corrugated process of Honeycomb manufacture is normally used to produce products in the higher density range. In this process adhesive is applied to the corrugated nodes, the corrugated sheets are stackedinto blocks, the node adhesive cured, and sheets are cut from these blocks to the required core Process of Honeycomb ManufactureRollSheetAdhesiveHOBE BlockHOBE SliceExpanded SheetWebExpansion ProcessThe Honeycomb fabrication process by the expansion method begins with the stacking of sheets of thesubstrate material on which adhesive node lines have been adhesive lines are then cured to form a HOBE ( Honeycomb Before Expansion) HOBE block itself may be expanded after curing to give an expanded block.

6 Slices of the expanded block may then be cut to the desired T , HOBE slices can be cut from the HOBE block to the appropriate T dimension and subsequently expanded. Slices can be expanded to regular hexagons,underexpanded to 6-sided diamonds, and overexpanded to nearly rectangular expanded sheets are trimmed to the desired L dimension (ribbon direction) and W dimension (transverseto the ribbon).99 HXDH1679 Rv. HW HC Guide 11/24/99 2:37 PM Page 6 Hexagonal CoreThe standard hexagonal Honeycomb is the basic and most common cellular honeycombconfiguration, and is currently available in allmetallic and nonmetallic OX configuration is a hexagonal honey-comb that has been overexpanded in the W direction, providing a rectangular cell configuration that facilitates curving or formingin the L OX process increases W shear Properties and decreases L shear Properties when compared to hexagonal Hexagonal CoreReinforced Honeycomb has a sheet of substratematerial placed along the nodes in the ribbondirection to increase the mechanical Cell Configurations4 HexWeb Honeycomb Attributes and PropertiesTWdirectionLdirectionTWdirecti onLdirectionLdirectionWdirectionT99 HXDH1679 Rv.

7 HW HC Guide 11/24/99 2:37 PM Page 75 Flex-Core The Flex-Core cell configuration provides forexceptional formability in compound curvatureswith reduced anticlastic curvature and withoutbuckling the cell walls. Curvatures of very tightradii are easily formed into tightradii, Flex-Core provides higher shear strengthsthan comparable hexagonal core of equivalentdensity. Flex-Core is manufactured from aluminum,Nomex , and fiberglass is a unique large cell Flex-Core for excellent formability and high specific compression Properties . Double-Flex is the most formable cell Tube-Core configuration provides a uniquelydesigned energy absorption system when thespace envelope requires a column or small diameter cylinder. The design eliminates the loss of crush strength that occurs at the unsupportededges of conventional isconstructed of alternate sheets of flat aluminumfoil and corrugated aluminum foil wrapped around a mandrel and adhesively bonded.

8 Outsidediameters can range from 1/2 inch to 30 inchesand lengths from 1/2 inch to 36 ConfigurationsHexcel can design and fabricate special geometrics in response to specific Rv. HW HC Guide 11/24/99 2:37 PM Page 8 Aluminum HoneycombHexcel aluminum honeycombs are designated as follows:Material Cell Size Alloy Foil Thickness DensityExample:CR III 1/4 5052 .002N :CR III signifies the Honeycomb is treated with a corrosion-resistant coating1/4 is the cell size in fractions of an inch5052 is the aluminum alloy is the nominal reference foil thickness ininchesN indicates the cell walls are nonperforated (P indicates perforated) is the density in pounds per cubic footCorrosion-Resistant CoatingsCorrosion-resistant coatings consist of a base layerunderlying a primer layer. Aluminum Honeycomb is available with two different corrosion-resistant coating are CR III chromate-based andCR-PAA phosphoric acid corrosionresistant coating is applied to the foil before the nodeadhesive is placed on the foil, thereby ensuring corrosion protection over the full foil IIICR III corrosion-resistant coating consists of a chro-mate-based protective layer and an organo-metallicpolymer.

9 CR III corrosion-resistant coating has beenspecified by the military for almost 30 phosphoric acid anodized coating providessuperior performance in certain instances. CR-PAA is superior with regards to: bond strength to aluminum facings in sandwich panel applications salt spray environments resistance to crack propagation hot/wet environmentsAluminum Honeycomb is available in four differentalloys, aerospace grades 5052 and 5056, and commercialgrades 3104 and AlloySpecification grade Honeycomb in the 5052 H39 aluminum alloy is available for general purpose applications, in a very wide range of cell size/densitycombinations in the hexagonal and Flex-Core configurations. OX-Core and underexpanded cell configuration can also be AlloySpecification grade Honeycomb in the 5056 H39 aluminum alloy offers superior strength over 5052alloy Honeycomb .

10 It is also available in a broad range of cell size/density combinations in the hexagonal andFlex-Core strength Properties of5056 alloy Honeycomb are approximately 20% greaterthat the comparable Properties of 5052 alloy honey-comb of similar cell size, foil gauge, and Aluminum Commercial Grade (ACG) Honeycomb provides a low-cost aluminum Honeycomb product for industrial ACG materials are provided with CR III coating. Hexcel produces ACGfrom 3000 series aluminum alloys. 3003 aluminumalloy is used for energy absorption applications whereprevious qualification studies specified this particularalloy. Hexcel also uses 3104 alloy for the manufactureof Honeycomb with the flexibility to provide either3104 or 3003 ACG, whichever is more appropriate forthe Honeycomb Attributes and Properties6 Honeycomb Materials* Perforated Honeycomb is used when the curing of the core-to-skin adhesive results in volatiles that must be vented, and in space applications where the atmospheremust be evacuated.