Fiber-reinforced composite material with improved fire resistance, and structural component made thereof

Abstract

A fiber-reinforced composite material includes a bulk portion with a bulk matrix having reinforcing fibers embedded therein, and a surface portion with a plurality of laminated first layers serving as expanding layers, which expand and/or delaminate during fire impact. The surface portion also includes a plurality of laminated second layers different from the first layers and serving as barrier layers. The expanding layers and barrier layers can be arranged in an alternating sequence.

Claims

1. A fiber-reinforced composite material, comprising: a multilayer bulk portion forming a bulk of the fiber-reinforced composite material and comprising a plurality of fiber material layers embedded in a bulk matrix; and a surface portion comprising a plurality of laminated first layers structurally configured to expand or delaminate during fire impact and a plurality of laminated second layers different from the plurality of laminated first layers, wherein the plurality of laminated first layers are arranged in an alternating sequence with the plurality of laminated second layers, wherein at least one of the laminated first layers comprises a thermoplastic film, the thermoplastic being a polymer selected from a group consisting of Polyimide, Polyetherimide, Polyether sulfone, Polyamide, Polyamide-imide, Polysulfone, Polyphenylsulfone, Polyetherketone, Polyethylene terephthalate, Polyethylene, Polyester, Polyetherester, Polyesteramide, Polymethylmethacrylate, Polypropylene, Polystyrene, Polyvinylchloride or mixtures thereof.

2. The fiber-reinforced composite material of claim 1, wherein at least one of the plurality of laminated first layers comprises fibers.

3. The fiber-reinforced composite material of claim 1, wherein at least one of the plurality of laminated first layers comprises an intumescent modifier.

4. The fiber-reinforced composite material of claim 1, wherein at least one of the plurality of laminated first layers has a thickness in a range of 5 to 300 m.

5. The fiber-reinforced composite material of claim 1, wherein at least one of the plurality of laminated first layers has a thickness in a range of 10 to 200 m.

6. The fiber-reinforced composite material of claim 1, wherein at least one of the plurality of laminated first layers has a thickness in a range of 20 to 130 m.

7. The fiber-reinforced composite material of claim 1, wherein at least one of the plurality of laminated first layers has a thickness of approximately 125 m.

8. The fiber-reinforced composite material of claim 1, wherein at least one of the plurality of laminated second layers comprises a surface matrix with embedded reinforcing fibers.

9. The fiber-reinforced composite material of claim 1, wherein at least one of the plurality of laminated second layers comprises a polymer.

10. The fiber-reinforced composite material of claim 1, wherein at least one of the plurality of laminated second layers comprises a resin matrix with inorganic particles dispersed in the resin matrix.

11. The fiber-reinforced composite material of claim 1, wherein at least one of the plurality of laminated second layers comprises a resin matrix with organic particles dispersed in the resin matrix.

12. The fiber-reinforced composite material of claim 1, wherein the plurality of laminated first layers are configured to expand or delaminate during fire impact above 100%.

13. A structural component, comprising: a fiber-reinforced composite material, comprising a multilayer bulk portion forming a bulk of the fiber-reinforced composite material and comprising a plurality of fiber material layers embedded in a bulk matrix; and a surface portion comprising a plurality of laminated first layers structurally configured to expand or delaminate during fire impact and a plurality of laminated second layers different from the plurality of laminated first layers, wherein the plurality of laminated first layers are arranged in an alternating sequence with the plurality of laminated second layers, wherein at least one of the laminated first layers comprises a thermoplastic film, the thermoplastic being a polymer selected from a group consisting of Polyimide, Polyetherimide, Polyether sulfone, Polyamide, Polyamide-imide, Polysulfone, Polyphenylsulfone, Polyetherketone, Polyethylene terephthalate, Polyethylene, Polyester, Polyetherester, Polyesteramide, Polymethylmethacrylate, Polypropylene, Polystyrene, Polyvinylchloride or mixtures thereof, and wherein structural component is a component of an aerial vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) The invention will be described hereinafter with reference to an exemplary embodiment with reference to the accompanying drawings. In these drawings:

(2) FIG. 1 shows a multi-layer design of a fiber-reinforced composite material,

(3) FIG. 2 shows the material of FIG. 1 during exposure to fire,

(4) FIG. 3 shows the heat release rate vs. time for a multi-layer design of a fiber-reinforced composite material and of a reference before and during exposure to fire, and

(5) FIG. 4 shows a perforated thermoplastic film as used for an expanding layer.

DETAILED DESCRIPTION

(6) FIG. 1 is a schematic cross section of a fiber-reinforced composite plastic (FRCP) 10 according to an embodiment of the present invention.

(7) The material 10 is a two-dimensional extending sheet material and consists of a bulk portion 12 and a surface portion 14.

(8) The bulk portion 12 comprises a bulk matrix with reinforcing fibers embedded therein. Preferably, the inner structure of the bulk portion 12 (which is not detailed shown in FIG. 1), is a conventional structure. Especially, the bulk portion 12 can be provided as a conventional epoxy matrix system with carbon or glass fibers embedded therein. The fibers may be provided e.g. in the form of one or preferably more fiber mats (woven or non-woven fabric), which are impregnated in advance or infused during a manufacturing process with the respective epoxy resin. In a curing step, completing the manufacturing process, the bulk portion 12 and the surface portion 14 have been cured and bonded together.

(9) The surface portion 14 serves for an increased fire protection and consists of at least expanding layers (first layers) 20-1, 20-2, and in the shown example also of barrier layers (second layers) 22-1, 22-2.

(10) The expanding layers 20 and the barrier layers 22 are arranged in an alternating sequence (expanding-barrier-expanding-barrier) on top of the bulk composite 12, thus forming a surface laminate protecting the underlying bulk composite 12 in an event of exposure to fire at the side on which the bulk composite 12 is covered by the surface laminate 14. In this respect, different from the shown example, in which the bulk composite 12 is covered only on one side, the bulk composite 12 may also be covered on both sides with a surface laminate of the kind described herein.

(11) The fire-protecting effect of the surface laminate 14 substantially relies on a particular behavior of the expanding layers 20. Namely, when these expanding layers 20 are heated due to exposure to fire (cf. flames 24 symbolized in FIG. 2), the expanding layers 20 increase their thickness (expand, e.g. by some kind of foaming) and/or loose their binding to adjacent layers (delaminate). This behavior leads to a decrease of the thermal conductivity of the surface laminate 14, retarding the rise in temperature in the bulk composite 12.

(12) FIG. 2 illustrates the material 10 during the impact of fire, symbolized by the flames 24.

(13) As can be seen from a comparison between FIG. 1 and FIG. 2, the fire causes the surface laminate 14 to heavily (or at least substantially) expand, so that the further progress of heat from the fire towards the bulk portion 12 is impeded.

(14) In the original (intact) state of the material 10, the outer expanding layer 20-2 and the outer barrier layer 22-2 have thicknesses d1 and d2, respectively, shown in FIG. 1. The thickness of the bulk composite is designated by d0.

(15) In the exposed (heated) state as shown in FIG. 2, the layers 20-2 and 22-2 have thicknesses d1 and d2 respectively (The thickness of the bulk composite 12 is designated by d0). In this situation, the thickness d1 is heavily increased in comparison to the original thickness d1. In practice, depending on the design of the expanding layer 20-2, this increase in thickness may result in an thickness d1, which is more than 10, preferably more than 20 times the thickness of d1. FIGS. 1 and 2 are not drawn in scale. They shall only illustrate the qualitative modification of the surface laminate 14 during fire impact.

(16) Preferably, the expanding layers 20 are designed to show the expanding and/or a delaminating effect already during the early stages of fire. Advantageously, these layers 20 begin to expand and/or delaminate remarkably already at temperatures of less than 400 C., preferably less than 250 C.

(17) As there will be a temperature gradient in the material 10 during the heating, the heat-induced effects are stronger in the outer regions (near the surface of the material) than in the inner regions. This is also illustrated in FIG. 2, in which the inner expanding layer 20-1 is also expanded with respect to the original state shown in FIG. 1, but not as much as the outer expanding layer 20-2.

(18) In the shown example, there is no remarkable change of the thickness of the barrier layers 22-1 and 22-2. The barrier layers 22 (second layers) are different from the expanding layers 20 (first layers) and serve to impede a transport of heat and/or gases through these layers. In the shown example, the barrier layers 22 in particular prevent oxygen from the outside air from diffusing to the combustible matrix of the bulk composite 12 and prevents gaseous combustible products from the bulk composite 12 from diffusing towards the outside (ignition zone).

(19) In the shown embodiment, the expanding layers 20 each are formed by a thermoplastic film, e.g. made of PEI or PES, and containing intumescent modifiers. In the example, these films contain foaming agents for promoting the increase of thickness induced by heat. In addition or as an alternative, the films may also contain fiber material, e.g. loose fibers embedded in the thermoplastic material or a fiber mat extending in the thermoplastic film.

(20) Preferably, each of the expanding layers 20 (in this example: 20-1 and 20-2) has a thickness in the range of 5 to 100 m, increasing at least by a factor of 10 when heated to its expansion temperature (e.g. approx. 300 C. or less).

(21) In the shown example, the barrier layers 22 (22-1 and 22-2) each comprise a surface matrix (e.g. resin) with reinforcing fibers embedded therein. In the shown example, short fibers dispersed in a matrix of polyamideimide or polyimide are used. In another embodiment, the material of the surface matrix is identical to the material of the bulk matrix (e.g. an epoxy resin system). This can facilitate the manufacture of the composite material 10 insofar as an infusion process can be provided to simultaneously infuse the bulk portion 12 and the surface portion 14. In principle, instead of short fibers in the barrier layers 22, there can be also used continuous fibers extending in these layers.

(22) Any kinds of fibers incorporated in the expanding layers 20 will advantageously increase the mechanical strength of the surface laminate 14. This distinguishes the described example from conventional, established forms of intumescent and barrier type fire protection.

(23) FIG. 3 shows the heat release rate vs. time for a multi-layer design of a fiber-reinforced composite material 10 and of a reference before and during exposure to fire.

(24) In the shown example of FIG. 3 a specimen or sample of a composite 10 having a thickness of 4 mm has been used. In this example two expanding layers 20, 20-1, 20-2 are used. The thickness of the expanding layers 20, 20-1, 20-2 is 125 m. The expanding layers 20 are made of a thermoplastic film. In this example Polyetherimid has been used.

(25) Two barrier layers 22, 22-1, 22-2 are arranged in alternating sequence with the expanding layer. The thickness of the barrier layers 22, 22-1, 22-2 is 250 m. The barrier layers 22, 22-2, 22-2 are of the same material as the bulk portion 12, so that the thickness of the barrier layer 22, 22-1, 22-2 can be increased without a loss in mechanical properties. The bulk portion 12 comprises carbon reinforced epoxy resin. It shall be noted that similar results can be achieved for barrier layers 22, 22-1, 22-2 of different material than the bulk portion 12.

(26) The expanding layers 20, 20-1, 20-2 are perforated with a needle in a rectangle perforation pattern. The perforation distance is 1 cm and the aperture 25 diameter is 1 mm.

(27) FIG. 3 shows the heat release rate of the before mentioned composite 10 and the heat release rate of a reference 26. The reference 26 is a conventional bulk material as known in the state of the art which does not have a multi-layer design. The reference 26 has a thickness of 4 mm.

(28) Both, the composite 10 having the expansion layers 20, 20-1, 20-2 and barrier layers 22, 22-1, 22-2 as described above, as well as the reference 26 are loaded with a heat flux of 25 kW/m.sup.2. Higher heat fluxes are possible; in that case the time to ignition could be lower and the peak heat release higher.

(29) In FIG. 3 the heat release rate is shown on the vertical axis and the time on the horizontal axis. The reference 26 ignites between 200 and 300 seconds and goes out after the combustible material is consumed after 500 seconds.

(30) For the composite 10 the outer expanding layer 20-2 which is the nearest to the heat source starts to expand and/or delaminate before ignition, i.e. before 60 seconds, as shown in FIG. 3. The time to ignition decreases compared to the reference 26. After ignition and 200 seconds after loading the composite 10 with the heat flux the combustible part of the outer barrier layer 22-2 has been consumed and/or carbonized. This can be seen as a first peak P1 for heat release, which is significantly lower than the heat release of the reference 26.

(31) After the combustible part of the outer barrier layer 22-2 has been consumed and/or carbonized, the heat release decreases until the protection from the outer expanding layer 20-2 decreases and the inner barrier layer 22-1 between the expansion layers 20-1 and 20-2 starts to burn, so that the heat release increases again to a second peak P2 of approximately the same size as the first peak P1.

(32) After both barrier layers, the outer barrier layer 22-2 and the inner barrier layer 22-1, are consumed and/or carbonized, the heat release decreases to a minimum Min. In some tests performed with the composite 10 as described above and under the same conditions, an extinction of the flame has been observed at the Minimum Min.

(33) After collapse of the expanding layers 20-1, 20-2 the rest of the material (the bulk portion 12) starts to decompose and the heat release rises again to a maximum Max.

(34) The maximum Max of the heat release of the composite 10 is lower than the peak heat release rate of the reference 26 and decreases until the combustible material of the bulk portion 12 is consumed at about 800 seconds.

(35) In FIG. 4 a perforated thermoplastic foil as used for expanding layers 20 is shown.

(36) A needle perforation has been used to create the apertures 25 in the film. A hexagonal perforation pattern is provided. The perforation distance is 20 mm. The apertures 25 are holes having a diameter of 1 mm.

(37) A preferred use of the fiber-reinforced composite material 10 is the formation of shell-like structural components for aerial vehicles, in particular airplanes or helicopters. The expandable thermoplastic interleaves (expanding layers 20) cause a remarkably increased fire protection of the respective structural components.

(38) Although in the described example the bulk portion and the surface portion are distinguishable from each other, the alternating expanding layers and barrier layers might take up 100% of the laminate (fiber-reinforced composite material). In this case, the bulk portion and the surface portion have the same layer structure or may be even identical. In such material, in particular, the barrier layers may be formed by layers which are conventional for forming fiber-reinforced composite material. In addition and alternatively, the above-described particular barrier layers may also be used (including also barrier layers made of metal etc.).

(39) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

LIST OF REFERENCE NUMERALS

(40) 10 Fiber-reinforced composite material 12 Bulk portion 14 Surface portion 20 Expanding layers 20-1 Inner expanding layer 20-2 Outer expanding layer 22 Barrier layers 22-1 Inner barrier layer 22-2 Outer barrier layer 24 Flames 25 Aperture 26 Reference P1 First peak P2 Second peak Min Minimum Max Maximum