Patent Description:
Various industries include components having multi-dimensional panels for various uses. For example, the aerospace industry utilizes nacelles for various applications for providing a protective housing around adjacent components as well as for providing an aerodynamic surface for reducing drag, among other applications. For example, a fan cowl is used for covering various components of a turbine engine and provides an aerodynamic surface for the turbine engine and related systems. A fan cowl outer skin is typically made from metal or carbon fiber thermoset composites. A current method of forming skins and/or stiffeners includes laying up thermoset composite plies by hand, one at a time, to form a laminate structure, representing a time consuming process.

<CIT> discloses a heat blanket assembly for forming a composite charge.

<CIT> discloses a method of forming multilayer composite panels with a specular surface.

According to an aspect of the present invention, a method for forming a thermoplastic panel is provided in accordance with claim <NUM>.

Optionally, when the thermoplastic resin comprises a crystalline structure, the forming temperature is greater than a recrystallization temperature of the thermoplastic resin.

Optionally, when the thermoplastic resin comprises an amorphous structure, the forming temperature is greater than a glass transition temperature of the thermoplastic resin.

Optionally, the at least one roller and the heating element are coupled to the thermoforming apparatus, the at least one roller and the heating element move together with the thermoforming apparatus.

Optionally, the thermoforming apparatus is moved along a track system with respect to the mandrel.

Optionally, in response to the thermoforming apparatus moving with respect to the mandrel, a trajectory of the thermoforming apparatus conforms to the shape of the mandrel.

Optionally, the at least one roller is compressed against the skin via a spring member.

Optionally, the method further comprises heating, via the heating element, the stiffener feature to the forming temperature.

Optionally, the method further comprises compressing, via the at least one roller, the stiffener feature between the skin and the mandrel in response to the at least one roller of the thermoforming apparatus being rolled along the skin, wherein the stiffener feature and the skin are consolidated together in response to being compressed by the at least one roller.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. Thus, the detailed description herein is presented for purposes of illustration only and not for limitation. For example, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Surface shading lines may be used throughout the figures to denote different parts but not necessarily to denote the same or different materials.

Throughout this specification, reference is made to "melting temperature" and "recrystallization temperature" in respect of thermoplastics. It is understood that the terms are defined as follows:
"Melting temperature" is the temperature range at which the plastic undergoes a phase change from a solid to liquid, upon heating.

"Recrystallization temperature" is the temperature at which the semi-crystalline or crystalline matrix begins to form crystals upon cooling from the molten amorphous state. The onset of re-crystalisation from the molten state takes place over a temperature "window-range', which is dependant on the rate of cooling and the final achievable degree of crystallinity of the polymer matrix.

The thermoplastic panel roll forming process, as described herein, may provide a relatively quick manufacturing process, e.g., on the order of minutes, of a thermoplastic panel, such as the outer skin for a stiffened panel. The thermoplastic panel roll forming process, as described herein, may provide a manufacturing process for transforming a flat thermoplastic panel into a relatively complex geometry, while minimizing, or eliminating, wrinkling.

With reference to <FIG>, a stiffened panel half <NUM> is illustrated, in accordance with various embodiments. Stiffened panel half <NUM> may comprise an outer skin <NUM>. Outer skin <NUM> may comprise a semi-cylindrical geometry when viewed from the aft direction, as shown in the illustrated embodiment. Outer skin <NUM> may define a centerline axis <NUM>. Stated differently, outer skin <NUM> may be bent around centerline axis <NUM>.

With reference to <FIG>, a section view of stiffened panel half <NUM> is illustrated, in accordance with various embodiments. Outer skin <NUM> may be contoured along the longitudinal direction (i.e., the Z-direction). Stated differently, outer skin <NUM> may comprise a non-linear geometry (e.g., rounded) along the longitudinal direction.

Outer skin <NUM> may be made from a fiber-reinforced thermoplastic material. In various embodiments, the outer skin <NUM> comprises a continuous reinforcing fiber and a thermoplastic resin. The reinforcing fiber to be used for the outer skin <NUM> has no particular limitations with respect to the type thereof, and examples thereof include metal fibers, such as an aluminum fiber, a brass fiber, and a stainless steel fiber, carbon fibers (including graphite fibers), such as polyacrylonitrile (PAN)-based carbon fibers, rayon-based carbon fibers, lignin-based carbon fibers, and pitch-based carbon fibers, insulating fibers, such as glass fiber, organic fibers, such as aramid fibers, polyparaphenylene benzoxazole (PBO) fibers, polyphenylene sulfide fibers, polyester fibers, acrylic fibers, nylon fibers, and polyethylene fibers, and inorganic fibers, such as silicon carbide fibers and silicon nitride fibers. Fibers prepared by applying surface treatment to these fibers are also available. Examples of the surface treatment include treatment with a coupling agent, treatment with a sizing agent, treatment with a binder, and adhesion treatment with an additive in addition to deposition treatment with conductive metal.

In the disclosure, the thermoplastic resin to be used for the outer skin <NUM> may be either crystalline or amorphous.

Examples of the crystalline thermoplastic resin include polyester, polyolefin, polyoxymethylene (POM), polyamide (PA), polyarylene sulfide, polyketone (PK), polyetherketone (PEK), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyaryletherketone (PAEK), polyether nitrile (PEN), fluororesin, and liquid crystal polymer (LCP). Examples of the polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terphthalate (PTT), polyethylene naphthalate (PEN), and liquid crystal polyester. Examples of the polyolefin include polyethylene (PE), polypropylene (PP), and polybutylene. Examples of the polyarylene sulfide include polyphenylene sulfide (PPS). Examples of the fluororesin include polytetrafluoroethylene.

Examples of the amorphous thermoplastic resin include polystyrene, polycarbonate (PC), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyphenylene ether (PPE), polyimide (PI), polyamide imide (PAI), polyetherimide (PEI), polysulfone (PSU), polyether sulfone (PES), and polyarylate (PAR). The thermoplastic resin to be used for the outer skin <NUM> also may be phenoxy resin, polystyrene, polyolefin, polyurethane, polyester, polyamide, polybutadiene, polyisoprene, fluorine resin, acrylonitrile, and other thermoplastic elastomers, and copolymers and modified resin thereof.

With reference to <FIG>, a method <NUM> for manufacturing a thermoplastic panel is provided, in accordance with various embodiments. Method <NUM> includes tacking together a plurality of plies of material comprising thermoplastic resin and fiber to form a skin (step <NUM>). Method <NUM> includes securing an edge of the skin with respect to a mandrel (step <NUM>). Method <NUM> includes heating the skin to a forming temperature (step <NUM>). Method <NUM> includes moving a thermoforming apparatus with respect to the mandrel (step <NUM>). Method <NUM> includes rolling at least one roller of the thermoforming apparatus along the skin in a direction away from the clamped edge of the skin, whereby the skin is compressed, consolidated, and conformed to a shape of the mandrel in response thereto (step <NUM>). Method <NUM> includes cooling the skin (step <NUM>).

With combined reference to <FIG> and <FIG>, step <NUM> may include stacking plies of fiber sheets <NUM> and thermoplastic resin sheets <NUM> to a desired thickness to form a skin preform <NUM> (also referred to herein as a skin). In various embodiments, and for ease of handling, the sheets may be stacked on a substantially planar surface <NUM>. In various embodiments, the resin sheets <NUM> may be "tacky" at a room temperature. Therefore, the resin sheets <NUM> may be "tacked" or stick to adjacent fiber sheets <NUM> without adding additional heat. However, in various embodiments, local heat may be applied to tack the resin sheets <NUM> and fiber sheets <NUM> together to form a flat sheet of material. Various methods may be used to tack together the stack of sheets to hold the sheets in place with respect to each other without departing from the scope of the present disclosure, such as clamping and ultrasonic welding, among others. Furthermore, any number of plies of fiber sheets <NUM> and/or resin sheets <NUM> may be used depending on the desired thickness of the fiber-reinforced thermoplastic panel. Furthermore, the thickness of the panel may vary. In this regard, a first location of the panel may have a first number of plies and a second location of the panel may have a second number of plies, different from the first number of plies. After the skin preform <NUM> has been formed, the skin preform <NUM> may be transferred to a mandrel <NUM> (see <FIG>).

With combined reference to <FIG> and <FIG>, step <NUM> may include securing an edge <NUM> of the skin preform <NUM> with respect to mandrel <NUM>. In this manner, edge <NUM> of skin preform <NUM> may be fixed with respect to mandrel <NUM> to secure skin preform <NUM> in place for roll forming. In various embodiments, edge <NUM> of skin preform <NUM> in secured in place by clamping, via clamp <NUM>, edge <NUM> to mandrel <NUM>.

With combined reference to <FIG> and <FIG>, step <NUM> may include heating, via one or more heating elements (e.g., heating element <NUM> and/or heating element <NUM>), the skin preform <NUM> to a forming temperature. Skin preform <NUM> may be locally heated to a sufficient forming temperature such that the skin preform <NUM> becomes pliable for roll forming purposes. In various embodiments, the term "forming temperature" as used herein may refer to a range of temperatures which is greater than the recrystallization temperature (or glass transition temperature for amorphous thermoplastic resins) of the thermoplastic resin of skin preform <NUM>. The suitable pliable forming temperature may vary depending on the particular thermoplastic material being used, as well as other factors, such as the thickness of the panel. In various embodiments, the forming temperature is a temperature below the melting temperature, but not less than the recrystallization temperature (or glass transition temperature for amorphous thermoplastic resins) of the thermoplastic. In various embodiments, the forming temperature is a temperature above the melting temperature of the thermoplastic.

With combined reference to <FIG> and <FIG>, step <NUM> may include moving a thermoforming apparatus <NUM> with respect to the mandrel <NUM>. Thermoforming apparatus <NUM> may comprise a structural frame <NUM>, heating element <NUM>, heating element <NUM>, first row of rollers <NUM>, and second row of rollers <NUM>. Heating element <NUM>, heating element <NUM>, first row of rollers <NUM>, and second row of rollers <NUM> may be mounted to structural frame <NUM>. Structural frame <NUM> may be mounted to a track system <NUM> whereupon thermoforming apparatus <NUM> is operatively coupled for moving thermoforming apparatus <NUM> with respect to mandrel <NUM> for roll forming the skin preform <NUM>. In various embodiments, structural frame <NUM> is made from a metal material. The dashed line at <NUM> also represents a trajectory of thermoforming apparatus <NUM>. This trajectory may conform to the profile of mandrel <NUM>. In this regard, step <NUM> may include moving thermoforming apparatus <NUM> along track system <NUM> with respect to the mandrel <NUM>. In various embodiments, thermoforming apparatus <NUM> is moved using an automated system. In this regard, an automated system may further include a controller, electric motors, and/or other system components for moving thermoforming apparatus <NUM> along track system <NUM>. However, in accordance with various embodiments, thermoforming apparatus <NUM>, may be moved manually by hand.

In various embodiments, track system <NUM> may conform to the shape of a contact surface of mandrel <NUM>. In this manner, thermoforming apparatus <NUM> may follow the profile of mandrel <NUM> as the thermoforming apparatus <NUM> is moved along the track system <NUM>. Mandrel <NUM> may exhibit a substantially convex geometry. In this regard, track system <NUM> may similarly exhibit a substantially convex geometry.

In response to thermoforming apparatus <NUM> moving with respect to the mandrel <NUM>, at least one roller may roll along skin preform <NUM> to form skin preform <NUM> against mandrel <NUM>. In this regard, step <NUM> may include rolling the first row of rollers <NUM> and the second row of rollers <NUM> along skin preform <NUM>. The first row of rollers <NUM> and the second row of rollers <NUM> may start at or near the clamped edge <NUM> of skin preform <NUM> and roll along skin preform <NUM> in a direction away from the clamped edge <NUM>. With skin preform <NUM> locally heated by heating element <NUM> and/or heating element <NUM> to a temperature below the melting temperature of the thermoplastic resin, the skin preform <NUM> is pliable, allowing the force applied by the first row of rollers <NUM> and the second row of rollers <NUM> against skin preform <NUM> to compress skin preform <NUM> against mandrel <NUM> (between the rollers and the mandrel), consolidate the plurality of plies of material (e.g., resin sheets <NUM> and fiber sheets <NUM>) of skin preform <NUM>, and further conform the geometry of skin preform <NUM> to that of the mandrel <NUM>.

Heating element <NUM> and/or heating element <NUM> may comprise any suitable heating element including infrared heaters, resistive heating elements, or the like. Heating element <NUM> may be configured to heat a first surface of skin preform <NUM>. Heating element <NUM> may be configured to heat a second, opposite surface of skin preform <NUM>. Heating element <NUM> may be configured to heat mandrel <NUM>. Heating element <NUM> may be configured to heat stiffener <NUM> (see <FIG>).

The first row of rollers <NUM> may be spring loaded. In this regard, the first row of rollers <NUM> may comprise at least one spring member <NUM> (also referred to herein as a first spring member). Similarly, the second row of rollers <NUM> may be spring loaded. In this regard, the second row of rollers <NUM> may comprise at least one spring member <NUM> (also referred to herein as a second spring member). The first spring member <NUM> and the second spring member <NUM> bias first row of rollers <NUM> and second row of rollers <NUM>, respectively, against skin preform <NUM>. As the thermoforming apparatus <NUM> moves with respect to mandrel <NUM>, the first spring member <NUM> and the second spring member <NUM> may extend and/or compress to allow the first row of rollers <NUM> and second row of rollers <NUM>, respectively, to conform to the geometry of mandrel <NUM>.

<FIG> illustrates thermoforming apparatus <NUM> with dotted lines between step <NUM> and step <NUM>. <FIG> illustrates thermoforming apparatus <NUM> with solid lines during step <NUM>.

In various embodiments, step <NUM> may include cooling the skin preform <NUM> after consolidating and conforming the skin preform <NUM> to the mandrel <NUM> to a temperature below a recrystallization temperature of the thermoplastic resin (e.g., room temperature) to form the hardened skin <NUM> (also referred to herein as a skin). In various embodiments, skin preform <NUM> is actively cooled. In various embodiments, skin preform <NUM> is passively cooled.

With reference to <FIG>, a section view of a portion of the thermoforming apparatus <NUM> and mandrel <NUM> is illustrated, in accordance with various embodiments. As illustrated in <FIG>, skin <NUM> may be curved along the hoop or circumferential direction (i.e., bent around longidutindal axis <NUM>). Furthermore, skin <NUM> may be curved along the longitudinal direction (i.e., curved along longidutindal axis <NUM>, or curved about a second axis <NUM> that is perpendicular to longidutindal axis <NUM>). First row of rollers <NUM> may extend along the entire length L of skin <NUM>. In this regard, the first row of rollers <NUM> may be rounded to conform to the geometry of mandrel <NUM>. Stated differently, the axis of rotation of each roller may be non-parallel, or at an angle, with respect to each adjacent roller. In various embodiments, the first row of rollers <NUM> may comprise a flexible roller system configured to bend with the geometry of mandrel <NUM>. In this regard, the first row of rollers <NUM> may be mounted on a flexible rod <NUM>. Various systems and methods of configuring a flexible roller system are contemplated herein, including flexible rods, rod segments hingedly coupled to each other, separate axle rods for each roller mounted at an angle with respect to each other to form a rounded row of rollers, etc..

Mandrel <NUM> comprises a channel <NUM> configured and sized to receive a plurality of plies of material (e.g., similar to skin <NUM> of <FIG>) to form a stringer or stiffener <NUM>. In this regard, prior to placing skin preform <NUM> on mandrel <NUM>, a stiffener preform may be placed at least partially into channel <NUM>. As the thermoforming apparatus <NUM> moves with respect to the mandrel <NUM>, the stiffener <NUM> may be heated by heating element <NUM>, with momentary reference to <FIG>, to a forming temperature and the rollers (i.e., first row of rollers <NUM> and second row of rollers <NUM>) may press skin preform <NUM> against stiffener <NUM> to consolidate the stiffener <NUM> and the skin preform <NUM> in a single stage process. In various embodiments, a secondary mandrel may be placed between the stiffener <NUM> and the skin <NUM> to help form and shape stiffener <NUM>. In various embodiments, channel <NUM> may be omitted from mandrel <NUM> and the skin <NUM> may be devoid of stiffeners and/or the stiffeners may be bonded to the skin <NUM> at a later stage.

Stiffener <NUM> may be coupled to skin <NUM> to provide reinforcement of the skin <NUM>. Such structural members may include, for example, ribs, spars, or frames configured to be attached to the skin of the fiber-reinforced thermoplastic structure. Such structural members may also include substantially elongated stiffener members often referred to as stringers or stiffeners. The stringers or stiffeners may be formed to exhibit various cross-sectional geometries including configurations such as I-beams, C-shapes or channels, J-shapes, Z-shapes, L-shapes or angles, omega shapes or what is often referred to as a hat shape or a hat channel. A stiffener or stringer exhibiting a cross-sectional geometry or profile of a hat essentially includes a cap member having a pair of web members, one web member extending from each end of the cap member at a defined angle relative thereto, and a pair of flange members with one flange member extending from each web member at a defined angle relative to the associated web member. In the cross-sectional geometry of some hat stiffeners, the flange members may be configured to be substantially parallel with the cap member.

With reference to <FIG>, the first row of rollers <NUM> may be offset from the second row of rollers <NUM>. The first row of rollers <NUM> may be offset from the second row of rollers <NUM> in a direction perpendicular, as illustrated by arrow <NUM>, to a direction of travel, illustrated by arrow <NUM>, of the first row of rollers <NUM> may be offset from the second row of rollers <NUM>. In this manner, each roller of the second row of rollers <NUM> may be substantially centered between each roller of the first row of rollers <NUM> to compress the entire surface of the skin <NUM> (see <FIG>), including locations that may be missed due to the spacing or gap between each of the rollers of the first row of rollers <NUM>.

However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the inventions. The scope of the inventions is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more.

Claim 1:
A method for forming a thermoplastic panel, comprising:
tacking together a plurality of plies of material comprising thermoplastic resin (<NUM>) and fiber (<NUM>) to form a skin (<NUM>), the plurality of plies of material are tacked together over a substantially planar surface (<NUM>);
clamping an edge (<NUM>) of the skin (<NUM>) to a mandrel (<NUM>);
heating, via a heating element, the skin (<NUM>) to a forming temperature;
moving a thermoforming apparatus (<NUM>) with respect to the mandrel (<NUM>);
rolling at least one roller of the thermoforming apparatus (<NUM>) along the skin (<NUM>) in a direction away from the clamped edge (<NUM>) of the skin (<NUM>) in response to the thermoforming apparatus (<NUM>) moving with respect to the mandrel (<NUM>), wherein the at least one roller is optionally compressed against the skin (<NUM>) via a spring member; and
in response to the at least one roller of the thermoforming apparatus (<NUM>) rolling along the skin (<NUM>), compressing the skin (<NUM>) between the at least one roller and the mandrel (<NUM>), consolidating the plurality of plies of material, and bending the skin (<NUM>) to conform to a shape of the mandrel (<NUM>); and
cooling the skin (<NUM>) after consolidating and conforming the skin (<NUM>) to the mandrel (<NUM>) to a temperature below a recrystallization temperature of the thermoplastic resin (<NUM>),
characterised in that the method further comprises:
disposing a second plurality of plies of material comprising thermoplastic resin and fiber to form a stiffener feature (<NUM>) in a channel (<NUM>) disposed in the mandrel (<NUM>).