GB2505871A

GB2505871A - Flame or heat resistant material comprising ceramic and carbon layers

Info

Publication number: GB2505871A
Application number: GB1213029.0A
Authority: GB
Inventors: Edward Watson Haynes; Steve Wise; Andrew John Gorton
Original assignee: WILLIAMS GRAND PRIX ENG
Current assignee: WILLIAMS GRAND PRIX ENG
Priority date: 2012-07-20
Filing date: 2012-07-20
Publication date: 2014-03-19
Also published as: WO2014013216A1; EP2874810A1; CN104602902A; GB201213029D0; JP2015530282A

Abstract

A multi-laminar material for the containment of heat and/or flame comprises a layer of ceramic material and a layer of carbon material. The ceramic is preferably alumina fibre paper. The carbon material is preferably carbon felt produced by pre-oxidising polyacrylonitrile. The preferred laminate comprises (in order) a structural layer, ceramic layer and carbon layer, and also adhesive or sealant layers. The preferred structural layer comprises a coated core, preferably a cellular metal, alloy or aromatic polyamide core, especially aluminium alloy honeycomb, coated with carbon fibre reinforced (CFR) thermoset epoxy or phenolic resin. The laminate is a fire guard, especially for a traction battery pack 12 for a motor vehicle with an adjacent fuel tank 14.

Description

FIRE GUARDS AND MATERIALS THEREFOR

The invention relates to multi-laminar materials for the containment of heat and/or flame, fire guards incorporating such materials and apparatus such as vehicles which incorporate such fire guards.

Some known batteries can malfunction, for example by catching fire if overcharged. This can not only be a problem in itself but can be even more problematic when such batteries are --located near to combustible material where there is scope for fire to spread to the combustible material.

The present invention aims to alleviate at least to a certain extent the problems of the prior art.

According to a first aspect of the present invention there is provided a multi-laminar material for the containment of heat and/or flame, the material comprising: a first protective layer comprising a ceramic material; and a second protective layer comprising carbon material.

In some embodiments, the first protective layer comprises an alumina, silica or aluminosilicate ceramic material. The ceramic material preferably comprises one or more layers of a ceramic paper. In a preferred embodiment, the first protective layer comprises one or more, preferably two, sheets of alumina fibre paper. The layer of ceramic material preferably has a thickness of about 2-lOmrn, preferably about 2-5mm.

In some embodiments, the second protective layer comprises a carbon material which may be a carbon felt or may be provided as a foam or a honeycomb structure. Preferably, the carbon material is a preToxidised pOlyacrylonitrile (PAN) carbon material. Preferably, the second protective layer comprises a carbon felt.

In some embodiments, the second protective layer has a thickness of about 1-5 mm, preferably about 1-4mm.

In some embodiments, the multi-laminar material further comprises a structural layer, S preferably located adjacent the first protective layer, The structural layer may be formed from any solid material, for example comprising polymeric material, metal, metal alloy or any mixture thereof In some embodiments, the structural layer is formed by a core material and a coating (such as a panel comprising a core material and a coating). The coating preferably comprises a thermoset resin. The thermoset resin coating may comprise carbon fibre reinforcement. The thermoset resin may be an epoxy-or phenolic-resin, preferably an epoxy resin, preferably with carbon fibre reinforcement. The core material may comprise a metal or metal alloy, such as an aluminium alloy (preferably a 5000 series aluminium alloy). In an alternative is -embodiment, the core material comprises an aramid polymeric material, preferably a meta-aramid. In certain embodiments, the core comprises a meta-aramid polymer, preferably poly(m-phenylene isophthalamide). The aramid, metal or metal alloy material is preferably provided as sheets, arranged to form a cellular structure, preferably where the cellular structure is in a honeycomb configuration. The structural layer preferably has a sandwich structure, with core material sandwiched between coating.

In some embodiments, the thickness of the structural layer is about 5-12mm, preferably about 6-9mm.

In the preferred multi-laminar material, the first protective layer is positioned adjacent the second protective layer. In a preferred embodiment, where a structural layer is present, the first protective layer may be positioned between the structural layer and the second protective layer. In some embodiments, sealant and/or adhesive may be present between any of the structural, first protective and second protective layers, or external thereto.

In some embodiments, the ratio of the thicknesses of first proteciive layer:second protective layer is 2:1 to 1:1. In some embodiments, the ratio of thickness of structural layer:first protective layer: second protective sayer is 6-3:2-1:1.

A further aspect of the invention provides a fire guard which includes a sheet of material in accordance with the above aspect of the invention.

A further aspect of the invention provides a fire-guarded chamber which includes a battery pack located in a chamber thereof, the chamber including a fire guard as in the previous aspect hereof.

At least a top wall of the chamber may be formed of the sheet of material.

The chamber may be sealed or substantially sealed.

The fire-guarded chamber may include a port arranged to open from the chamber to an exterior space upon application of a predetermined pressure at the port, the port being located on an underside of the chamber, the port preferably comprising a burst disk.

A further aspect of the invention provides a fire-guarded chamber which contains a battery pack and includes a port arranged to open from the chamber to an exterior space upon application of a predetermined pressure to the port, the port being located on an underside of the chamber, the port preferably comprising a burst disk.

A further aspect of the invention provides apparatus including a fire-guarded chamber as in any of the aspects hereof set out above and a tank arranged to contain a combustible friel.

The tank may be located adjacent or above the fire-guarded chamber.

The apparatus may comprise a motor vehicle, such as a motor land vehicle. Application in other environments such as UPS systems, aircraft or spacecraft is also envisaged.

The battery pack may comprise a traction battery pack of the motor vehicle.

The traction battery pack may be arranged to supply electrical energy to (andlor receive power from) a powertrain motor (or generator) of the motor vehicle.

The generator is operable to supply electrical energy for charging the battery pack upon transmission of a signal indicative of a braking bominand issued within the vehicle.

The present invention may be canied out in various ways and preferred materials and apparatus in accordance with the invention will now be described by way of example only and with rcfcrcnce to the accompanying drawings, in which: Figure 1 is a schematic view of a motor vehicle which includes a preferred fire-guarded battery pack chamber using preferred multi-laminar material in accordance with a preferred embodiment; Figure 2 is a schematic view of the battery pack chamber; Figure 3 is a view of the battery pack chamber from underneath; and Figure 4 is a view of the battery pack chamber with a lid thereof removed.

There now follows a non-limiting detailed discussion.

A ceramic material' as referred to herein is an inorganic crystalline material. It should be appreciated that where the ceramic material is an alumina, silica or aluminosilicate ceramic, 2S other components may also be present within the ceramic crystalline structure. Thus, in an alumina ceramic, alumina is the predominant oxide present, but other oxides including silica may also be present.

A ceramic paper' as referred to herein is a type of ceramic material in the form of a flexible sheet comprising ceramic fibres and optionally a binder. The ceramic fibres should be refractory any may, for example, be refractory alumina fibres.

Carbon fibres may be derived from polyacrylonitrile (PAN). A "pre-oxidized polyacrylonitrile carbon material" is a material formed from pie-oxidized PAN carbon fibres which may optionally have undergone further processing, for example to form a felt. The pre-S oxidized material may undergo oxidation or may, preferably, be present in a pre-oxidised form.

A carbon felt' as referred to herein is a non-woven, carbon-containing fabric, which may be formed by compression of carbon fibres. A carbon felt is preferably formed from pre-oxidized polyacrylonitrile (PAN) carbon material. This may be referred to as a pie-oxidized PAN carbon felt.

An aluminium alloy' as referred to herein is an alloy in which alumiuium is present, preferably as the predominant metal (by weight). Other elements present may include, for is example, Cu, Mg, Mn, Si and Zn. An aluminium alloy as used herein is preferably an aluminium magnesium alloy, for example, a 5000 series aluminium alloy.

An aiamid' as referred to herein is an aromatic polyamidc. An aramid is preferably an aromatic polyamide in which at least least 85% of the amide linkages are attached directly to two aromatic rings.

A honeycomb' structure or configuration comprises an array of hollow cells formed between walls. The cells are generally hexagonal in shape.

EXAMPLES

Test Procedure The test procedure used to assess the suitability of the multi-laminar material for use in a contaimnent system for a lithium-ion battery was based on FAA Advisory Circular 20-135:

POWERPLANT INSTALLATION AND PROPULSION SYSTEM COMPONENT FIRE

-PROTECTION TEST METHODS, STANDARDS, AND CRITERIA.

A test material was mounted with a gas flame to impinge directly on to the test material * surface at a distance of approximately 20mm. The temperature achieved in the test set-up was between 980°C and 1020°C, using a Propane gas cylinder. For the purposes of comparative S testing, a 1000°C flame temperature was the target.

A propane gas torch was set at a short distance from the face of the test material. A thermocouple set in front of the test material surface measured the "flame" temperature. On the other side of the panel a thermocouple was bonded in a central position with tape. The two temperatures were monitored throughout the test using the Fluke multimeter. Fine gas adjustments were made to maintain flame maximum temperature. In general, initial flame temperatures were approximately 960°C, climbing to 1020°C after ten or more minutes.

The requirements for a material suitable for use in a containment system of the invention are that the material has minimal thickness, minimal weight, is capable of resisting a flame with temperature 1000°C directly on the surface for 15 minutes or more, while maintaining structural integrity, and providing sufficient thermal insulation to protect a fuel container which may be positioned in a vehicle adjacent the containment system.

The multi-laminar material of the invention was found to perform remarkably well and meet the above criteria, in contrast to a large number of other combinations of materials which were not able to satisfy the above requirements.

Materials tested for the protective layers included pre-oxidised PAN carbon felt, titanium alloy foil, silica aerogel, ceramic sheets, polyimide foam (Solimide®), refractory alumina fibre paper (Kaowool 1600 Paper), and alumina-boria-silica fibre fabric (Nextel ® 312), in various combinations as shown in Table 1. Various sandwich panel materials were tested for the structural layer. Panel core materials included Nomex ® (poly(m-phenylene isophthalamide)), aluminium alloy, and a ceramic board (Cotronics 360-1).

Test Material Test end Test end outer Duration of Condition ofl No Combination inner face face test outer face, temperature temperature (minutes) where not (°C) (°C) satisfactory 01 Nomex+Ti+ 1050 243 6 C-felt xl 02 Nomex + C-felt 985 309 6 xl 03 Nomex -f Ti + 1000 250 15 -Blistered C-felt xl 04 Nomex + C-felt 972 286 6 Flames from xl -I-Ti edges.

Ceramie+Ti+ 1026 230 15 C-felt xl 06 Ceramic + C-1008 266 15 felt xl 07 Ceramic+ C-1016 214/230/ 15128/40 feltx2 220 08 Ceramic + 973 276 9.5 Aerogel Aerogel degraded 09 Al-core + C-Felt 999 254 16 x2 Nomex+C-felt 1020 274/218 15/25 Fuelbag x2 (with fuel material bag material degraded attached to outer face) 11 Nomex + 1008 282 15 Ceramic sheet Ceramic sheet degraded 12 Nomex+ 1033 189/197 16/30 Ceramic+x 1 C-felt I 13 Nomex + 1007 258 15 Seam intact, Ceramic but very weak (machined to 3mm)+xl C-felt (stitched seam) 14 AI-core+ 1040 206 15 Ceramie+xl C-felt ( stitched seam) Nomex+3nijn 1031 226 15 Kaowool + C--felt 16 Nomex+3nim 1041 232 15 Kaowool + Panther felt with glass 17 Nomex+ 1025 252 15 Kaowool FP + C-felt + Nextel 312 AF1O 18 Nomex panel + 1042 264 15 Evonik P1 Evonik + C-felt foam degraded + Nextel (used) -stuck to I CFRP panel Table 1: Material combinations tested and test summary. The inner face is that closest to the gas flame.

The pre-oxidised PAN non-woven carbon felt was demonstrated to provide a superior flame barrier. In the most severe test, the felt suffered only minor degradation after 40 minutes of direct flame impingement with temperatures in excess of 1000 °C. The titanium alloy foil performed badly when used as a direct flame barrier. Significant distortion and discolouration was observed, and the heat protection provided for the CFR-epoxy sandwich panel behind it

S

was very poor. Ceramic shect (Cotronics 360-1) was intact after 15 minutes exposure with direct flame impingement on the surface, but the top layers were significantly degraded. The results shown in Table indicate that a ceramic and carbon felt combination provides advantageous protective properties in comparison to other materials.

A multi-laminar material taken forward to testing in a full scale test battery containment box comprised a combination of two layers of 1.4 mm thick Kaowool 1600 ceramic paper (88% alumina, 9% silica, 3% other oxides) and one layer of pre-oxidized PAN non-woven carbon felt at nominal thiclmess 1.8 mm. A structural layer was provided comprising a sandwich panel with an aluminium alloy (5052 alloy) honeycomb core (6.525 mm thick) and carbon-fibre reinforced epoxy matrix skinSeachid (0.6 miKiliibk each). An aluminium alloy was used in the tested material because of its higher strength as shown in stress analysis. For some applications, alternative core materials could be used. For example, an alternative and lighter core material is a Nomex® honeycomb core.

In testing of the test battery containnent box, following ignition of Lithium ion battery cells, the fire was allowed to burn until exhaustion. The external temperature did not exceed 50°C.

When disassembled, the structural integrity of the multilaminar material had not been compromised. It was concluded that this combination of materials is suitable for contaji-ment of a lithium ion battery.

The advantageous preferred materials described herein may advantageously be incorporated in a containment system to give fire resistance in the event of battery ignition, due to over-charging. or some other malfunction. Such containment systems have thus advantageously been found to be capable of limiting the spread of both flames and heat for a period of 15 minutes or more. -Figure 1 shows an example of a motor land vehicle 10 in accordance with one embodiment, the vehicle including a fire-guarded battery pack chamber 12 located below a fuel tank 14 for supplying combustible liquid or gaseous fuel via a fuel line 16 to a combustion engine 18 (such as an IC engine) for supplying tractive power to at least one ground drive wheel 20 of the motor land vehicle 10.

The battery pack chamber 12 contains a Lithium-based (e.g. Lithium-ion) traction battery system 22 which is arranged to power the vehicle along by tractive electric motor power together with or as an alternate power source to the engine 18, the traction battery system also being chargeable in a conventional manner such as by a generator (not shown) of the vehicle 10, e.g. driven from the engine 18 andlor by regenerative braking functionality, the generator in one example being reconfigurable as an electric motor to provide the tractive electric motor power mentioned above.

As shown in Fig. 4, thc battery system 22 is secured to a rectangular base 24 of the chamber 12 by supports 26. The chamber 12 also has a lid 28 which has a rectangular top surface 30 and four rectangular sides 32 (two of which are shown in Fig. 2), the four sides 32, lid 28 and base 24 forming a sealed or substantially sealed enclosure containing the battery system 22 when the lid 28 is secured down onto the base 24.

At least the top surface 30 of the lid 28 and preferably also at least parts of and typically all of the sides 32 of the lid 28 are made from multi-laminar material comprising a carbon fibre reinforced-epoxy skinned sandwich panel with an aluminium alloy honeycomb core, plus two sheets of alumina fibre ceramic paper, supplemented with one layer of pre-oxidised PAN non-woven carbon felt, with the ceramic paper and carbon felt held in place with a covering comprising a one ply aramid-epoxy composite fabric. Optionally, the base 24 is also made of this material.

The base 24 incorporates a relief port in the form of a circular aperture 34 formed therethrough and positioned below the battery system 22, a circular burst disk 36 being located within the circular aperture 34.

In the event of a malfunction of the battery system, such as overcharging, resulting in fire there is firstly a limited amount of oxygen available to feed the fire. In the event of continued fire and a pressure build-up within the chamber 12, the relief port 34, 36 may advantageously open at a predetermined pressure by means of bursting of the burst disk 36. Accordingly, a catastrophic pressure build is advantageously avoided so that the chamber 12 cannot explode or otherwise release pressure in an uncontrolled manner. Furthermore, the relatively small S burst aperture 34 may allow a flow of fire combustion products out of the chamber 12 while restricting the counterflow of oxygen-containing air into the chamber 12. Furthermore, the combustion products are advantageously ejected downwardly out of the chamber and away from the fuel tank 14.

Furthermore, while the fire is burning and if it continues to do so, the preferred laminate material used in the construction of the chamber 12 provides excellent flame guarding and thermal transfer restriction performance for a continued period which may exceed 15 minutes.

Even with the thel tank 14 containing combustible fuel and positioned near to, next to or above the chamber 12, the excellent performance of the chamber 12 helps ensure that fire andlor heat do not easily cause fire to break out at or in the region of the fuel tank or elsewhere in the motor land vehicle 10.

It is envisaged that in other embodiments a plurality of similar relief ports 34, 36 may be provided through the base 24 of the chamber 12.

Various modifications to the specifically described examples are envisaged and are considered to fall within the scope of the present invention as defined by the accompanying claims as interpreted under patent law.

Claims

CLAIMS1. A multi-laminar material for the contaimnent of heat andlor flame, the material comprising: s a first protective layer comprising a ceramic material; and a second protective layer comprising carbon material.
2. A material as claimed in claim 1 in which the first protective layer comprises an alumina, silica or aluminosilicate ceramic material.
3. A material as claimed in claim 1 in which the ceramic material comprises one or more layers of ceramic paper.
4. A material as claimed in any preceding claim, wherein the first protective layer is comprises one or more layers of alumina fibre paper.
5. A material as claimed in any preceding claim iii which the layer of ceramic material preferably has a thickness of about 2-10mm, preferably about 2-5mm.
6. A material as claimed in any preceding c'aim in which the second protective layer comprises a carbon felt.
7. A material as claimed in any preceding claim in which the carbon material is a pre-oxidized polyacryonitri1e carbon material.
8. A material as claimed in any preceding claim in which the second protective layer has a thickness of about 1-5 mm, preferably about 1-4mm.
9. A material as claimed in any preceding claim, wherein the material further comprises a structural layer.
10. A material as claimed in claim 9 in which the structural layer is formed by a panel comprising a core material and a coating.
11. A material as claimed in claim 10, in which the coating compriscs a thermoset resin.
12. A material as claimed in claim 10 or 11, wherein the coating comprises carbon fibre reinforcement.
11 A material as claimed in any of claims 10 to 12, in which the thermoset resin is an epoxy-or phenolic-resin, preferably with carbon fibre reinforcement.
14. A material as claimed in any one of claims 10 to 13 in which the core material comprises a metal alloy, a metal, an aramid polymeric material, or a mixture thereof
15. A material as claimed in any one of claims 10 to 14 in which the core material comprises an aluminium alloy.
16. A material as claimed in any one of claims 10 to 15 in which the core material is provided as sheets, arranged to form a cellular structure; preferably where the cellular structure is in a honeycomb configuration.
17. A material as claimed in any one of claims 10 to 16, in which the thickness of the structural layer is about S-l2mm, preferably about 6-9mm.
18. A material as claimed in any preceding claim in which the ratio of the thicknesses of first protective layer:second protective layer is 2:1 to 1:1.
19. A material as claimed in any one of claims 10 to 18 in which the first protective layer is positioned between the structural layer and the second protective layer.
20. A material as claimed in any preceding claim in which sealant and/or adhesive layers are present between any of the structural, first protective and second protective layers, or external thereto.
21. A fire guard which includes a sheet of material as claimed in any preceding claim.
22. A fire-guarded chamber which includes a battery pack located in the chamber, the chamber including a fire guard as claimed in claim 21.
23. A fire-guarded chamber as claimed in claim 22 in which at least a top wall of the chamber is formed of the sheet of material.
24. A fire-guarded chamber as claimed in claim 23 in which the chamber is sealed or substantially sealed.
25. A fire-guarded chamber as claimed in claim 24 which includes a port arranged to open from the chamber to an exterior space upon application of a predetermined pressure at the port, the port being located on an underside of the chamber, the port preferably comprising a burst disk.
26. A fire-guarded chamber which contains a battery pack and includes a jort arranged to open from the chamber to an exterior space upon application of a predetermined pressure to the port, the port being located on an underside of the chamber, the port preferably comprising a burst disk.27 Apparatus including a fire-guarded chamber as any one of claims 22 to 26 and a tank arranged to contain a combustible fuel.28. Apparatus as claimed in claim 27 in which the tank is located adjacent or above the fire-guarded chamber.29. Apparatus as claimed in claim 27 or claim 28 which comprises a motor vehicle.30. Apparatus as claimed in claim 29 in which the battery pack comprises a traction battery pack of the motor vehicle.S3 1. Apparatus as claimed in claim 30 in which the traction battery pack is arranged to supply electrical energy to (andlor receive power from) a powertrain motor (or generator) of the motor vehicle.32. Apparatus as claimed in claim 31 in which the generator is operable to supply electrical energy for charging the battery pack upon transmission of a signal indicative of a braking command issued within the vehicle.33. A material substantially as described herein with reference to the accompanyingexamples.34. A fire-guarded chamber substantially as described herein with reference to the accompanying drawings.35. A motor land vehicle substantially as described herein with reference to the accompanying drawings.