USH47H - Panel with aramid honeycomb core - Google Patents

Panel with aramid honeycomb core Download PDF

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Publication number
USH47H
USH47H US06/734,192 US73419285A USH47H US H47 H USH47 H US H47H US 73419285 A US73419285 A US 73419285A US H47 H USH47 H US H47H
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United States
Prior art keywords
resin
panel
facing
fabric
spunlaced fabric
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US06/734,192
Inventor
Mohamed M. Monib
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EIDP Inc
Original Assignee
EI Du Pont de Nemours and Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by EI Du Pont de Nemours and Co filed Critical EI Du Pont de Nemours and Co
Priority to US06/734,192 priority Critical patent/USH47H/en
Assigned to E.I. DU PONT DE NEMOURS AND COMPANY reassignment E.I. DU PONT DE NEMOURS AND COMPANY ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: MONIB, MOHAMED M.
Application granted granted Critical
Publication of USH47H publication Critical patent/USH47H/en
Abandoned legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
    • B32B3/10—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material
    • B32B3/12—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material characterised by a layer of regularly- arranged cells, e.g. a honeycomb structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/12—Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C2/00—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels
    • E04C2/30—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by the shape or structure
    • E04C2/34—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by the shape or structure composed of two or more spaced sheet-like parts
    • E04C2/36—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by the shape or structure composed of two or more spaced sheet-like parts spaced apart by transversely-placed strip material, e.g. honeycomb panels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/40—Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2607/00—Walls, panels

Definitions

  • This invention relates to a lightweight structural panel having a honeycomb aramid core which is faced with a resin-impregnated fiber layer. More particularly, the invention concerns such a panel having significantly increased peel strength between the facing layer and the core and a process for making the improved panel.
  • a lightweight structural panel having an aramid honeycomb core faced with a resin-impregnated fiber layer is known.
  • Such panels have been used in aircraft for lightweight structural members, such as floorings, window panels, overhead luggage storage bins, and the like.
  • Panels having high strength and stiffness have been made with facing layers in the form of resin-impregnated woven fabrics or cross-laid, unidirectional tapes made from high-strength, high-stiffness yarnsof poly(p-phenylene terephthalamide), fiberglass, or carbon.
  • a phenolic resin is usually used for the facing impregnant because of its low emission of smoke and toxic gases under fire conditions.
  • the facing layer is adhered to the aramid honeycomb core by activation and curing of the resin. Only a small fraction of the honeycomb cross-section consists of solid material. The solid material is only in the walls which form the cells of the honeycomb. Thus, there is very little area on the surface of the honeycomb core to which the impregnated-fiber facing layer adheres. Because of the small area available for adhesion, the peel strength between the facing layer and the aramid honeycomb core of the above-described panels often is less than desired. Accordingly, an object of the present invention is to provide such a panel with increased peel strength between the core and the facing.
  • the invention provides an improved lightweight structural panel having an aramid honeycomb core faced with a resin-impregnated fiber layer.
  • the improvement comprises, for increased peel strength between the core and facing layer, a spunlaced fabric composed of at least 50% by weight of aramid fibers, said fabric being pervaded with the resin, being located between the facing layer and the core and providing a strong bond between the core and facing.
  • the aramid fibers of the spunlaced fabric are of poly(m-phenylene isophthalamide).
  • Preferred spunlaced fabric has a unit weight in the range of 15 to 30 g/m 2 . Phenolic resins are preferred.
  • Preferred facing layers are resin-impregnated woven fabrics of poly(p-phenylene terephthalamide) yarns.
  • the invention also includes a process for making the improved panel.
  • the process comprises forming an assembly of an aramid honeycomb core, a spunlaced fabric which includes at least 50% by weight of aramid fibers, and a resin-impregnated fiber facing layer, by interposing the spunlaced fabric between and adjacent to the surface of the honeycomb and a surface of the facing layer, heating the assembly to cause resin from the facing to pervade the interposed spunlaced fabric and curing the resin to bond the assembly.
  • PPD-T refers to poly(p-phenylene terephthalamide) polymer
  • MPD-I refers to poly(m-phenylene isophthalamide) polymer
  • the lightweight structural panels include, as important components an aramid honeycomb core, a resin-impregnated facing layer, and a spunlaced nonwoven fabric.
  • the spunlaced fabric, which is pervaded by the resin is located between a surface of the honeycomb and the facing layer.
  • a sandwich structure is used. In the sandwich panel, the upper and lower surfaces of the aramid core are each bonded to a corresponding resin-impregnated facing layer with a spunlaced fabric interposed between each facing and the core.
  • Aramid honeycomb cores of the type suitable for use in the panels of the invention are known in the art.
  • the core is made of MPD-I paper.
  • Such aramid honeycomb cores are available commercially from Hexcel Corporation, Dublin, Calif. (e.g., HRH-10 aramid fiber reinforced honeycomb having an average cell size of about 3,2 mm [1/8 inch] and a nominal density of about 0.05 g/cm 3 [3.0 lbs./ft. 3] ).
  • HRH-10 aramid fiber reinforced honeycomb having an average cell size of about 3,2 mm [1/8 inch] and a nominal density of about 0.05 g/cm 3 [3.0 lbs./ft. 3] ).
  • the size of the cells, the density, the overall dimension and the strength and stiffness characteristics of the core can vary considerably, depending on the intended use of the panel.
  • the resin-impregnated fiber layer which forms the facing of the panels of the invention are made of woven fabrics or of cross-laid unidirectional tapes, of high-strength, high-stiffness yarns. Yarns of PPD-T polymer are preferred. Many resins are suitable for use in the invention but phenolic resins are preferred. Curable phenol formaldehyde resins are particularly preferred. The amount of resin employed in the facing may vary widely. Add-ons of 50 to 200% based on the dry weight of the facing yarns generally are suitable. Add-ons of 70 to 130% are preferred. The total weight of the facing fabric also may vary considerably depending on the intended use of the panel. For example, resin-impregnated facings having a unit weight in the range of 70 to 500 g/m 2 (2-15 oz/yd 2 ) are generally useful, with unit weights of 200 to 400 g/m 2 being preferred.
  • the fabric that is interposed between the facing and the surface of the aramid core of the lightweight structural panel of the invention is made by the general methods disclosed by Bunting et al., U.S. Pat. No. 3,508,308.
  • the fabric is a spunlaced nonwoven fabric composed of at least 50% by weight staple aramid fibers or blends of such fibers with other staple fibers such as polyester fibers.
  • the preferred aramid fibers are of MPD-I polymer.
  • the staple fibers are formed into carded and cross-lapped batts which are then fed to a staple-fiber, air-lay, web-forming machine which forms a lightweight, uniform, random batt.
  • Batt weights of 25 to 60 g/m 2 are generally useful, though somewhat heavier or lighter batts may also be used. Preferred batt weights are in the range of 30 to 45 g/m 2 .
  • the thusly formed batt is then passed through a series of high impact, small-diameter columnar jets of water which entangle the staple fibers into a strong, stable, spunlaced fabric. Nonapertured spunlaced fabrics are preferred.
  • the spunlace fabric is stretched transversely by about 60% to reduce its unit weight, preferably to a weight in the range of 15 to 25 g/m 2 .
  • the fabric is then calendered.
  • the calendering typically is performed under high pressure and at temperatures of about 240 to 250° C. The calendering makes the web thinner, but does not impair its ability to act as a carrier for the resin of the facing in the final assembly. It has been found that the thinner the stretched and calendered spunlaced fabric, the stronger the bond that is generally obtained between the facing and the honeycomb core of the final panel.
  • the process of the invention involves forming an assembly of the above-described components, heating and curing the resin to fully bond the assembly.
  • the spunlaced fabric is positioned between the resin-impregnated facing layer and the surface of the honeycomb core to which the facing is to be attached.
  • the components are held firmly together and then heated to activate the resin.
  • the resin pervades the spunlaced fabric. Further heating cures the resin and forms a strong bond among the components.
  • the heating and curing may be performed in an autoclave or in a vacuum bagging operation.
  • This example illustrates the invention with the fabrication of a strong, lightweight sandwich panel.
  • the example also demonstrates the large advantage in peel strength that is obtained with panels of the invention over panels made by a prior-art method in which no spunlaced fabric is included in the structure.
  • Continuous filament yarns of 1267 dtex (1140-denier) of poly(p-phenylene terephthalamide) polymer (Kevlar® 49 aramid yarn sold by E. I. du Pont de Nemours and Company, Wilmington, Del.) were woven into a crowfoot weave fabric (Kevlar® Style 285 fabric) having an end count of 6.7 ⁇ 6.7 per cm (17 ⁇ 17 per inch) and a unit weight of 173 g/m 2 (5.1 oz/yd 2 ).
  • the fabric was impregnated with a curable phenol formaldehyde resol ("WeyRez-X 5000" phenolic resin, a product of Weyerhaeuser Co., Tacoma, Wash.) in the form of a solution containing 50% by weight solids.
  • a curable phenol formaldehyde resol (“WeyRez-X 5000" phenolic resin, a product of Weyerhaeuser Co., Tacoma, Wash.) in the form of a solution containing 50% by weight solids.
  • Two layers of the impregnated fabric were placed upon a plastic film atop a flat metallic plate.
  • the impregnated fabric was air dried to drive out the solvent. A dry basis add-on of 100% was achieved.
  • the impregnated fabrics were placed one atop the other and then placed thereupon was a layer of spunlaced fabric of a blend of 60 wt.
  • the layer of spunlaced fabric was next placed a layer of poly(m-phenylene isophthalamide) honeycomb measuring 35.6 cm (14 inches) on each side and 1.27 cm (0.5 inch) in thickness.
  • the honeycomb core was a product of Hexcel Corporation, Dublin, Calif.
  • Another sheet of the spunlaced fabric was placed on top of the honeycomb and two more layers of the resin-impregnated fabrics were placed atop the spunlaced fabric.
  • the thusly prepared assembly was vacuum bagged and cured at a temperature of 126° C. and a pressure of 310kPa (45 psi).
  • the cured product was a sandwich panel (designated below as "Test Panel") comprising a laminate of an aramid honeycomb core having upper and lower facing layers, with spunlaced fabric interposed between the core and the facing layers.
  • the test panel was cut into strips measuring 7.6-cm wide by 30.5-cm long (3 ⁇ 12 inches).
  • the strip samples were tested for Climbing Drum Peel Strength in accordance with Military Standard No. MIL-STD-401A of "Sandwich Constructions and Core Materials: General Test Methods", U.S. Department of Defense, Sept. 26, 1967.
  • Control samples were prepared in the same manner as the test panels, except that the spunlaced sheet were omitted. The control samples were also tested for peel strength. The results of the measurements were as follows:

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  • Engineering & Computer Science (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Laminated Bodies (AREA)

Abstract

A lightweight structural panel having an aramid honeycomb core faced with a resin-impregnated fiber layer is provided with increased peel strength between the core surface and facing layer by interposing a spunlaced fabric containing at least 50 weight percent aramid fibers and being pervaded with the resin between the core and the facing. Phenolic resins and woven facing fabrics of poly(p-phenylene terephthalamide) yarns are preferred.

Description

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a lightweight structural panel having a honeycomb aramid core which is faced with a resin-impregnated fiber layer. More particularly, the invention concerns such a panel having significantly increased peel strength between the facing layer and the core and a process for making the improved panel.
2. Description of the Prior Art
A lightweight structural panel, having an aramid honeycomb core faced with a resin-impregnated fiber layer is known. Such panels have been used in aircraft for lightweight structural members, such as floorings, window panels, overhead luggage storage bins, and the like. Panels having high strength and stiffness have been made with facing layers in the form of resin-impregnated woven fabrics or cross-laid, unidirectional tapes made from high-strength, high-stiffness yarnsof poly(p-phenylene terephthalamide), fiberglass, or carbon. For aircraft-interior applications, a phenolic resin is usually used for the facing impregnant because of its low emission of smoke and toxic gases under fire conditions.
In manufacture of the above-described panels, the facing layer is adhered to the aramid honeycomb core by activation and curing of the resin. Only a small fraction of the honeycomb cross-section consists of solid material. The solid material is only in the walls which form the cells of the honeycomb. Thus, there is very little area on the surface of the honeycomb core to which the impregnated-fiber facing layer adheres. Because of the small area available for adhesion, the peel strength between the facing layer and the aramid honeycomb core of the above-described panels often is less than desired. Accordingly, an object of the present invention is to provide such a panel with increased peel strength between the core and the facing.
SUMMARY OF THE INVENTION
The invention provides an improved lightweight structural panel having an aramid honeycomb core faced with a resin-impregnated fiber layer. The improvement comprises, for increased peel strength between the core and facing layer, a spunlaced fabric composed of at least 50% by weight of aramid fibers, said fabric being pervaded with the resin, being located between the facing layer and the core and providing a strong bond between the core and facing. Preferably, the aramid fibers of the spunlaced fabric are of poly(m-phenylene isophthalamide). Preferred spunlaced fabric has a unit weight in the range of 15 to 30 g/m2. Phenolic resins are preferred. Preferred facing layers are resin-impregnated woven fabrics of poly(p-phenylene terephthalamide) yarns.
The invention also includes a process for making the improved panel. The processcomprises forming an assembly of an aramid honeycomb core, a spunlaced fabric which includes at least 50% by weight of aramid fibers, and a resin-impregnated fiber facing layer, by interposing the spunlaced fabric between and adjacent to the surface of the honeycomb and a surface of the facing layer, heating the assembly to cause resin from the facing to pervade the interposed spunlaced fabric and curing the resin to bond the assembly.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
As used herein, PPD-T refers to poly(p-phenylene terephthalamide) polymer and MPD-I refers to poly(m-phenylene isophthalamide) polymer.
In accordance with the present invention, the lightweight structural panels include, as important components an aramid honeycomb core, a resin-impregnated facing layer, and a spunlaced nonwoven fabric. The spunlaced fabric, which is pervaded by the resin is located between a surface of the honeycomb and the facing layer. In a preferred panel, a sandwich structure is used. In the sandwich panel, the upper and lower surfaces of the aramid core are each bonded to a corresponding resin-impregnated facing layer with a spunlaced fabric interposed between each facing and the core.
Aramid honeycomb cores of the type suitable for use in the panels of the invention are known in the art. Preferably, the core is made of MPD-I paper. Such aramid honeycomb cores are available commercially from Hexcel Corporation, Dublin, Calif. (e.g., HRH-10 aramid fiber reinforced honeycomb having an average cell size of about 3,2 mm [1/8 inch] and a nominal density of about 0.05 g/cm3 [3.0 lbs./ft.3]). Of course, the size of the cells, the density, the overall dimension and the strength and stiffness characteristics of the core can vary considerably, depending on the intended use of the panel.
The resin-impregnated fiber layer which forms the facing of the panels of the invention are made of woven fabrics or of cross-laid unidirectional tapes, of high-strength, high-stiffness yarns. Yarns of PPD-T polymer are preferred. Many resins are suitable for use in the invention but phenolic resins are preferred. Curable phenol formaldehyde resins are particularly preferred. The amount of resin employed in the facing may vary widely. Add-ons of 50 to 200% based on the dry weight of the facing yarns generally are suitable. Add-ons of 70 to 130% are preferred. The total weight of the facing fabric also may vary considerably depending on the intended use of the panel. For example, resin-impregnated facings having a unit weight in the range of 70 to 500 g/m2 (2-15 oz/yd2) are generally useful, with unit weights of 200 to 400 g/m2 being preferred.
The fabric that is interposed between the facing and the surface of the aramid core of the lightweight structural panel of the invention, is made by the general methods disclosed by Bunting et al., U.S. Pat. No. 3,508,308. The fabric is a spunlaced nonwoven fabric composed of at least 50% by weight staple aramid fibers or blends of such fibers with other staple fibers such as polyester fibers. The preferred aramid fibers are of MPD-I polymer. In the process of making the spunlaced fabric, the staple fibers are formed into carded and cross-lapped batts which are then fed to a staple-fiber, air-lay, web-forming machine which forms a lightweight, uniform, random batt. Batt weights of 25 to 60 g/m2 are generally useful, though somewhat heavier or lighter batts may also be used. Preferred batt weights are in the range of 30 to 45 g/m2. The thusly formed batt is then passed through a series of high impact, small-diameter columnar jets of water which entangle the staple fibers into a strong, stable, spunlaced fabric. Nonapertured spunlaced fabrics are preferred.
In a preferred embodiment of the invention, the spunlace fabric is stretched transversely by about 60% to reduce its unit weight, preferably to a weight in the range of 15 to 25 g/m2. The fabric is then calendered. For preferred webs of at least 50% MPD-I fibers, the calendering typically is performed under high pressure and at temperatures of about 240 to 250° C. The calendering makes the web thinner, but does not impair its ability to act as a carrier for the resin of the facing in the final assembly. It has been found that the thinner the stretched and calendered spunlaced fabric, the stronger the bond that is generally obtained between the facing and the honeycomb core of the final panel.
The process of the invention involves forming an assembly of the above-described components, heating and curing the resin to fully bond the assembly. In the assembly the spunlaced fabric is positioned between the resin-impregnated facing layer and the surface of the honeycomb core to which the facing is to be attached. The components are held firmly together and then heated to activate the resin. As a result of the heating, the resin pervades the spunlaced fabric. Further heating cures the resin and forms a strong bond among the components. The heating and curing may be performed in an autoclave or in a vacuum bagging operation.
EXAMPLE
This example illustrates the invention with the fabrication of a strong, lightweight sandwich panel. The example also demonstrates the large advantage in peel strength that is obtained with panels of the invention over panels made by a prior-art method in which no spunlaced fabric is included in the structure.
Continuous filament yarns of 1267 dtex (1140-denier) of poly(p-phenylene terephthalamide) polymer (Kevlar® 49 aramid yarn sold by E. I. du Pont de Nemours and Company, Wilmington, Del.) were woven into a crowfoot weave fabric (Kevlar® Style 285 fabric) having an end count of 6.7×6.7 per cm (17×17 per inch) and a unit weight of 173 g/m2 (5.1 oz/yd2). The fabric was impregnated with a curable phenol formaldehyde resol ("WeyRez-X 5000" phenolic resin, a product of Weyerhaeuser Co., Tacoma, Wash.) in the form of a solution containing 50% by weight solids. Two layers of the impregnated fabric were placed upon a plastic film atop a flat metallic plate. The impregnated fabric was air dried to drive out the solvent. A dry basis add-on of 100% was achieved. The impregnated fabrics were placed one atop the other and then placed thereupon was a layer of spunlaced fabric of a blend of 60 wt. % of 1.7 dtex (1.5-denier), 1.9-cm (0.75-inch) long staple fibers of poly(m-phenylene isophthalamide) (Type-450 Nomex® aramid fiber sold by E. I. du Pont de Nemours and Company) and 40 wt % 1.5 dtex (1.35-denier), 1.9-cm (0.75-inch) long staple fibers of poly(ethylene terephthalate) (Type-106 Dacron® polyester fiber sold by E. I. du Pont de Nemours and Company). The spunlaced fabric had been stretched 60% in the cross machine direction to provide a unit weight of 20 g/m2 (0.6 oz/yd2) and then calendered at 245° C. under a load of 400 kg per linear centimeter. Upon the layer of spunlaced fabric was next placed a layer of poly(m-phenylene isophthalamide) honeycomb measuring 35.6 cm (14 inches) on each side and 1.27 cm (0.5 inch) in thickness. The honeycomb core was a product of Hexcel Corporation, Dublin, Calif. Another sheet of the spunlaced fabric was placed on top of the honeycomb and two more layers of the resin-impregnated fabrics were placed atop the spunlaced fabric. The thusly prepared assembly was vacuum bagged and cured at a temperature of 126° C. and a pressure of 310kPa (45 psi).
The cured product was a sandwich panel (designated below as "Test Panel") comprising a laminate of an aramid honeycomb core having upper and lower facing layers, with spunlaced fabric interposed between the core and the facing layers. The test panel was cut into strips measuring 7.6-cm wide by 30.5-cm long (3×12 inches). The strip samples were tested for Climbing Drum Peel Strength in accordance with Military Standard No. MIL-STD-401A of "Sandwich Constructions and Core Materials: General Test Methods", U.S. Department of Defense, Sept. 26, 1967.
Control samples were prepared in the same manner as the test panels, except that the spunlaced sheet were omitted. The control samples were also tested for peel strength. The results of the measurements were as follows:
______________________________________                                    
Peel Strength    Sample                                                   
(Force/unit width)                                                        
                 Control  Test Panel                                      
______________________________________                                    
Top Side                                                                  
Newtons/cm       1.9      6.7                                             
(lb/in)          (1.1)    (3.8)                                           
Bottom Side                                                               
Newtons/cm       2.9      11.6                                            
(lb/in)          (1.7)    (6.6)                                           
______________________________________
The results show that the panels of the invention were 31/2 to 4 times stronger in peel strength than the control panels.

Claims (8)

I claim:
1. In a lightweight structural panel having an aramid honeycomb core faced with a resin-impregnated fiber layer, the improvement comprising, for increased peel strength between the core surface and facing layer, a spunlaced fabric composed of at least 50% by weight of aramid fibers, said spunlaced fabric being pervaded by the resin, being located between the facing layer and the core surface and providing a strong bond between the core and the facing.
2. A panel in accordance with claim 1 wherein the aramid fibers of the spunlaced fabric are of poly (m-phenylene isophthalamide) polymer.
3. A panel in accordance with claim 1 wherein the spunlaced fabric has a unit weight in the range of 15 to 30 g/m2.
4. A panel in accordance with claim 1, 2 or 3 wherein the panel is a sandwich structure in which the honeycomb core has a second surface bonded to a spunlaced fabric and a facing layer in the same manner as the other surface.
5. A panel in accordance with claims 1, 2 or 3 wherein the resin is a phenolic resin and the facing layer is a resin-impregnated woven fabric of poly(p-phenylene terephthalamide) yarn.
6. A process for preparing an improved lightweight structural panel comprising forming an assembly of an aramid honeycomb core, a spunlaced fabric which includes at least 50% by weight of aramid fibers, and a resin-impregnated fiber facing layer, by interposing the spunlaced fabric between and adjacent to a surface of the honeycomb core and a surface of the facing layer, heating the assembly to cause resin from the facing to prevade the interposed spunlaced fabric and curing the resin to bond the assembly.
7. A process in accordance with claim 6 wherein the aramid fiabers of the spunlaced fabric are of poly(m-phenylene isophthalamide) polymer.
8. A process in accordance with claim 6 or 7 wherein the spunlaced fabric has a unit weight in the range of 15 to 30 g/m2.
US06/734,192 1985-05-15 1985-05-15 Panel with aramid honeycomb core Abandoned USH47H (en)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5085928A (en) * 1989-04-06 1992-02-04 E. I. Dupont De Nemours And Company Fiber reinforced composites comprising uni-directional fiber layers and aramid spunlaced fabric layers
US5277956A (en) * 1992-01-29 1994-01-11 The United States Of America As Represented By The Secretary Of The Air Force Enhanced reinforced honeycomb structure
US5320892A (en) * 1993-02-22 1994-06-14 E. I. Du Pont De Nemours And Company Tough layered papers with improved surface adhesion
EP0658644A2 (en) * 1993-12-17 1995-06-21 FISCHER ADVANCED COMPOSITE COMPONENTS GESELLSCHAFT m.b.H. Cloth, prepreg thereof, lightweight constructional element from such prepegs, overhead stowage bin for aircrafts
US5484500A (en) * 1990-10-09 1996-01-16 E. I. Du Pont De Nemours And Company Method for forming structural panels having a core with thermoplastic resin facings
US5714226A (en) * 1991-05-04 1998-02-03 Hoechst Aktiengesellschaft Porous honeycomb material and manufacture and use thereof
US20060108716A1 (en) * 2002-03-20 2006-05-25 Webasto Vehicle Systems International Gmbh Roof module for a motor vehicle and process for producing same
GB2477091A (en) * 2010-01-20 2011-07-27 Hexcel Composites Ltd Structureal laminate comprising face sheets, core and open-structured sheet

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5085928A (en) * 1989-04-06 1992-02-04 E. I. Dupont De Nemours And Company Fiber reinforced composites comprising uni-directional fiber layers and aramid spunlaced fabric layers
US5484500A (en) * 1990-10-09 1996-01-16 E. I. Du Pont De Nemours And Company Method for forming structural panels having a core with thermoplastic resin facings
US5714226A (en) * 1991-05-04 1998-02-03 Hoechst Aktiengesellschaft Porous honeycomb material and manufacture and use thereof
US5277956A (en) * 1992-01-29 1994-01-11 The United States Of America As Represented By The Secretary Of The Air Force Enhanced reinforced honeycomb structure
US5320892A (en) * 1993-02-22 1994-06-14 E. I. Du Pont De Nemours And Company Tough layered papers with improved surface adhesion
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