The present invention generally relates to a fiber preform for use in a resin transfer molding process, and more particularly to a fire retardant fiber preform for use in vehicle components that require fire resistance such as a battery box for containing battery cells of an electric vehicle.
Tailored Fiber Placement (TFP) is a textile manufacturing technique in which fibrous material is arranged on another piece of base material and is fixed with an upper and lower stitching thread on the base material. The fiber material can be placed in curvilinear patterns of a multitude of shapes upon the base material. Layers of the fiber material may be built up to produce a two-dimensional fiber preform insert, which may be used as an insert overmolding or resin transfer process to create composite materials.
Resin transfer molding or overmolding (hereafter referred to synonymously as “RTM”) is a process in which the fiber preform in placed in a mold where a melt processible material is molded directly into the insert. Melt processible materials typically used in overmolding include elastomers and thermoplastics. The major overmolding processes includes insert molding and two-shot molding. Materials are usually chosen specifically to bond together, using the heat from the injection of the second material to form that bond that avoids the use of adhesives or assembly of the completed part, and results in a robust composite material part with a high-quality finish.
Composite materials are increasingly used in industry because of their high strength to weight ratios. Weight savings are particularly important for electric and hybrid vehicles powered with energy cells employing battery technologies in order to achieve greater vehicle driving range per charge. However, unique problems associated with some components of electric and hybrid vehicles have hindered the ability to use composite materials for some applications on hybrid or electric vehicles. For example, batteries of electric and hybrid vehicles present unique safety considerations owing to the high voltages of the batteries, chemicals employed in the battery technologies, combustion and fire risks associated with the batteries, and potential fume encounters if the batteries are broken or damaged.
Thus, there exists a need for a novel fiber preform having fire retardant characteristics for use in forming vehicle components that require fire resistance for safety purposes and for a fire resistant vehicle component.
The present invention is further detailed with respect to the following drawings that are intended to show certain aspects of the present of invention, but should not be construed as limit on the practice of the invention, wherein:
A fiber preform for use in an overmolding process is provide that includes a fiber bundle arranged in a predetermined pattern and attached to itself with thread stitches to form at least one preform layer. At least one intumescent material is associated with the at least one preform layer.
A vehicle component having fire resistant characteristics is provided that includes a housing having a first side and a second side. The housing has a shape that defines the vehicle component. An intumescent material is provided on at least one of the first side and the second side of the housing.
The present invention has utility as a fiber preform having fire retardant characteristics for use in an overmolding process for forming vehicle components that require fire resistance for safety purposes, such as a battery box for containing battery cells of an electric vehicle. The present invention additionally has utility as a vehicle component having fire retardant characteristics and fire resistance for safety purposes, such as a battery box for containing battery cells of an electric vehicle.
It is to be understood that in instances where a range of values are provided that the range is intended to encompass not only the end point values of the range but also intermediate values of the range as explicitly being included within the range and varying by the last significant figure of the range. By way of example, a recited range of from 1 to 4 is intended to include 1-2, 1-3, 2-4, 3-4, and 1-4.
Referring now to the figures, a fiber preform 10 according to embodiments of the present invention includes a fiber bundle 14 arranged in a predetermined pattern and attached to itself by a plurality of stitches 18 of a thread to form at least one preform layer 11. The inventive fiber preform 10 additionally includes at least one intumescent material 50 associated with the at least one preform layer 11. According to embodiments, the intumescent material 50 is applied to a plurality of fibers 15, 16 that make up the fiber bundle 14, to an exterior surface 13 of the fiber bundle 14, the thread 18, a substrate 12 of the fiber preform 10, a surface of the at least one preform layer 11, or a combination thereof.
The fiber bundle 14 is arranged in a predetermined pattern by a selective comingled fiber bundle positioning (SCFBP) method and attached to itself, and/or according to embodiments a substrate 12, by a plurality of stitches 18 of a thread, which according to some embodiments is a thermoplastic thread formed of a nylon or polyethylene material. According to embodiments that include a substrate 12, the substrate 12 acts as a foundation or base upon with a fiber bundle 14 is applied. The substrate 12 may be a tear-off fabric or paper, a thermoset or thermoplastic sheet, or other suitable material. According to embodiments, the substrate 12 is used as a foundation upon which the fiber bundle 14 is applied in the predetermined pattern but is torn off prior to placement of the fiber preform 10 in a mold.
The predetermined pattern in which the fiber bundle 14 is arranged may generally resemble the shape of the designed final composite material component, for example a vehicle component 70 of an automobile, such as a battery containment construct for housing energy cells of an electric vehicle, such as that shown in cross section in
The fiber bundle 14 is attached to itself and/or to a substrate 12 by a plurality of stitches 18 of thread. In some embodiments, the thread is a thermoplastic thread, such as nylon or polyethylene. As shown in
The at least one intumescent material 50 associated with the at least one preform layer 11 provides fire resistance to the fiber preform 10 and ultimately the vehicle component 70 formed using the fiber preform 10, which is particularly useful for vehicle components that are subject to strict fire safety regulations such as components near or surrounding vehicle batteries. An intumescent material is one that undergoes a chemical change when exposed to heat or flames, becoming viscous, forming expanding bubbles that harden into a dense, heat insulating multi-cellular char. The objectives of intumescent technology are the containment of fire and toxic gases by inhibiting flame penetration, heat transfer and transport of toxic gases from the site of a fire to other parts of a structure. According to embodiments, an intumescent material 50 is provided on such vehicle components and when exposed to extreme heat or fire expands and chars to seal the vehicle component to resist fire penetration and prevent the spread of fumes. An intumescent is a substance that swells as a result of heat exposure, thus increasing in volume and decreasing in density. The term intumescent when applied to fire protective coatings refers to a technology wherein the coating will swell and form multi-layered char foam when exposed to heat. High carbon containing chars are extremely heat resistant and can be employed in critical high temperature applications such as the carbon on carbon composites that are machined to produce rocket exhaust nozzles. The production of these carbon on carbon composites involves the combination of graphite fibers with high char yield epoxies. After curing, these parts are graphitized in a high-pressure autoclave at high temperatures. Intumescent materials can be thermally stable to above 1,000° C. (1,832° F.). With the right choice of materials, intumescent coatings can produce a low thermally conductive char foam. Thus, a coating that includes an intumescent substance can form a char foam that has a low thermal conductivity when exposure to fire and/or extreme heat.
Soft char intumescent substances can produce a light char that is a poor conductor of heat, thus retarding heat transfer. Typically, these intumescent substances can also contain a significant amount of hydrates. As the hydrates are spent, water vapor is released, which has a cooling effect. Once the water is spent, the insulation characteristics of the char that remains can slow down heat transfer from the exposed side to the unexposed side of vehicle component 70 that includes an intumescent coating or sheet 50. Typically, the expansion pressure that is created for these products is very low, because the soft carbonaceous char has little substance, which is beneficial if the aim is to produce a layer of insulation. Harder char intumescent substances can be produced with sodium silicates and graphite. These intumescent substances can produce a more substantial char capable of exerting quantifiable expansion pressure.
Commercial examples of an intumescent substance that are available include INTUMAX manufactured by Broadview Technologies, Inc. located in Newark, N.J. Such intumescent agents can allow the use of less intumescent agent in a binder's formulation, which, in turn, can improve the physical and adhesive properties of the coatings. Many others sources of intumescent substances that can be added to binder materials are available.
Intumescent substances can be added to binder materials such as, but not limited to, acrylic resins, styrene-butadiene rubber (SBR), polyvinyl alcohol, ethyl vinyl acetate resins, phenolic resins, etc., and combinations thereof. These binder materials can be modified as desired to crosslink (e.g., with a crosslinking agent, such as melamine formaldehyde) or to change other characteristics such as hydrophobicity, hydrophilicity, viscosity, pH, etc. As such, other materials and components can be included within the intumescent coating. For example, waxes, plasticizers, rheology modifiers, antioxidants, antistats, antiblocking agents, and other additives may be included as desired. Surfactants may be added to help disperse some of the ingredients, especially the film-forming binder within the solvent system. When present, a surfactant(s) can be included in the heat resistant coating up to about 20%, such as from about 0.5% to about 5%. Exemplary surfactants can include nonionic surfactants and/or ionic surfactants.
A plasticizer may also be included in the intumescent coating. A plasticizer is an additive that generally increases the flexibility of the final coating by lowering the glass transition temperature for the binder (and thus making it softer). In one embodiment, the plasticizer can be present in the heat resistant coating 104 up to about 25%, such as from about 5% to about 20%, by weight. Likewise, viscosity modifiers can be present in the heat resistant coating. Viscosity modifiers are useful to control the rheology of the coatings in their application. A particularly suitable viscosity modifier is high molecular weight poly(ethylene oxide). The viscosity modifier can be included in any amount to help the coating process, such as up to about 5% by weight, such as about 0.5% to about 3% by weight.
According to embodiments, the intumescent material 50 is formed from thermoplastic fiber proximal to cellulosic fiber in various relative configurations provided within the fiber bundle 14. Such thermoplastic fibers operative herein illustratively include disparpolypropylenes, polyamides, polyesters, polyether ether ketones, polybenzobisoxazoles, polyphenylene sulfide; block copolymers containing at least of one of the aforementioned constituting at least 40 percent by weight of the copolymer; and blends thereof. Cellulosic fibers, synonymously referred to herein as cellulosics, operative herein include cotton, linen, rayon, bamboo, hemp, sisal, jute, and celluolose ether reaction products of any of the aforementioned. As used herein cellulose ethers include methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), hydroxyethylcellulose (HEC) and carboxymethylcellulose (CMC). Suitable cellulosic fibers, include, but are not limited to, natural and synthetic cellulosic fibers (e.g., cotton, rayon, acetate, triacetate, and lyocell, as well as their flame resistant counterparts FR cotton, FR rayon, FR acetate, FR triacetate, and FR lyocell). Examples of rayon fibers include Viscose™ and Modal™ by Lenzing, available from Lenzing Fibers Corporation. An example of an FR rayon material is Lenzing FR™, also available from Lenzing Fibers Corporation, and VISIL™, available from Sateri. Examples of lyocell fibers include TENCEL™, TENCEL G100™ and TENCEL A100™, all available from Lenzing Fibers Corporation. Examples of vinal fibers include Kuralon™ fibers available from Kuraray. The synthesis of cellulose ethers from cellulose is known to the art as detailed in P. Nasatto et al., “Methylcellulose, a Cellulose Derivative with Original Physical Properties and Extended Applications” Polymers 2015, 7, 777-803.
In still other embodiments, a coating of an intumescent material, such as that described above, referred to herein synonymously as a sizing, is applied to any fiber present in a fiber bundle. Coating materials operative herein illustratively include poly(vinylphosphonic acid); a mixture of ammonium polyphosphate, pentaerythritol and melamine; double-hydroxide modified phosphate esters in resin matrices; and combinations thereof. Thermoplastic sizing based on poly(vinylphosphonic acid) are detailed in B K Kandola et al. Molecules 2020, 25, 688-703. A cross-sectional view of a fiber 15 with an intumescent coating 50′ applied thereon is shown in
According to embodiments, a char layer is generated that is protective of the thermoplastic fibers within the fiber bundle 14. Without intending to be bound to a particular mechanism, it is believed that the cellulosic fiber material combusts with kinetic rapidity relative to the thermoplastic fiber content to generate a char residue that deposits on proximal thermoplastic within the fiber bundle 14. The alteration of the surface energy of the fiber bundle 14 with a fluorocarbon finish, results in fire resistivity being provided to the fiber bundle 14.
Proximity of thermoplastic fiber to cellulosic fiber is achieved by direct contact between adjacent fibers, or such fibers are separated by a distance of 1 to 3 fiber diameters therebetween. Fibers are in intimate contact given the length of the fibers and the blending process, some portion of cellulosic fibers will always make contact with the thermoplastic fibers. This proximity is achieved through conventional textile manufacture techniques using a yarn that include both thermoplastic fiber and cellulosic fiber content.
Typical fiber diameters according to such embodiments of the present invention are independent for each of the thermoplastic fiber and cellulosic fiber. It is appreciated that a variety of fiber diameters are readily spun together to form a yarn. Textile fibers are reported in denier (indirect measure of diameter). The denier of fibers used for both cellulosic and thermoplastic is roughly 1.5 denier. In inventive embodiments, the average fiber (based on number average) diameter ratio of the thermoplastic fiber:cellulosic fiber is 1:1, however the ratio may range from 0.8:1 to 1.2:1.
According to further embodiments, the intumescent material 50 is an intumescent graphite, which is an expandable graphite. Such intumescent graphite is advantageous in that it is biologically inert, non-toxic, free of heavy metals, halogen free, and insoluble in water and other solvents. According to embodiments, the expandable graphite has a start expansion temperature (SET) between 150 and 300° C., which may be tuned based on the processing conditions to be used with a given fiber preform 10 and its processing to a completed vehicle component. According to embodiments, the expandable graphite is provided as a coating, a putty, a strip, a foam, or a combination thereof. Expandable graphite is advantageous in that it expands under heat, fire, and/or pressure exposure. Additionally, expandable graphite is advantageous in that it has a neutral pH value, low initial viscosity, high SET, and small particle size. According to embodiments, the expandable graphite intumescent material 50 is applied to a plurality of fibers 15,16, 42, 44 that make up the fiber bundle 14, to an exterior surface 13 of the fiber bundle 14, the thread 18, a substrate 12 of the fiber preform 10, a surface of the at least one preform layer 11, or a combination thereof.
According to embodiments, the substrate 12 is formed of an intumescent sheet 50 or such an intumescent sheet is applied to a side of the preform 10 or to an already formed vehicle component 70, as shown in
Referring now to
In
As shown in
As shown in
According to embodiments, the fiber bundle 14 is made of reinforcing fibers, such as those made of 100% carbon, 100% glass, or 100% aramid fibers, or a combination thereof. According to certain embodiments, the fiber bundle 14 includes matrix fibers, being of a thermofusible nature may be formed from a thermoplastic material such as, for example, polypropylenes, polyamides, polyesters, polyether ether ketones, polybenzobisoxazoles, polyphenylene sulfide; block copolymers containing at least of one of the aforementioned constituting at least 40 percent by weight of the copolymer; and blends thereof. The thermoplastic fibers are appreciated to be recycled, virgin, or a blend thereof. The thermofusible thermoplastic matrix fibers have a first melting temperature at which point the solid thermoplastic material melts to a liquid state. The reinforcing fibers may also be of a material that is thermofusible provided their thermofusion occurs at a temperature which is higher than the first melting temperature of the matrix fibers so that, when both fibers are used to create a composite, at the first melting temperature at which thermofusibility of the matrix fibers occurs, the state of the reinforcing fibers is unaffected. As used herein, any reference to weight percent or by extension molecular weight of a polymer is based on weight average molecular weight. As used herein, the term melting as used with respect to thermoplastic fibers or thread is intended to encompass both thermofusion of fibers such that a vestigial core structure of separate fibers is retained, as well as a complete melting of the fibers to obtain a homogenous thermoplastic matrix. The thermoplastic fibers are appreciated to be recycled, virgin, or a blend thereof. The thermoplastic fibers in a comingled fiber bundle constitute from 20 to 80 weight percent of the comingled fibers in the present invention.
As shown in
The fiber preform 10 is tunable and easily changed and adapted for varying design requirements. The properties and characteristics of the fiber preform may be changed and modified based on controlling parameters of the various components of the fiber preform including parameters of the fiber bundle 14, the thread, and the plurality of stitches 18. Parameters of the fiber bundle may include, but are not limited to, a diameter of the fiber bundle, a ratio of the thermoplastic fibers to the reinforcing fibers, a composition of the thermoplastic fibers, and a composition of the reinforcing fibers. Parameters of the thread may include, but are not limited to, a denier of the thread, a composition of the thread, and a melting temperature of the thread. The parameters of the plurality of stitches 18 may include, but are not limited to, a linear distance between the stitches and a tension of the stitches.
The foregoing description is illustrative of particular embodiments of the invention, but is not meant to be a limitation upon the practice thereof. The following claims, including all equivalents thereof, are intended to define the scope of the invention.
This application is a non-provisional application that claims priority benefit of U.S. Provisional Application Ser. No. 63/256,621 filed Oct. 17, 2021; the contents of which are hereby incorporated by reference.
Number | Date | Country | |
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63256621 | Oct 2021 | US |