Patent Description:
Conventional processes for manufacturing a layup mandrel require designing a dedicated substructure specific for the layup mandrel, creating a face sheet (the surface molding the final part shape), attaching all the components together with adhesives and complex assembly (wet layups, fasteners, or welding). Manufacturing a composite face sheet requires machining a master mold, layup and cure of the face sheet, and then final machining to match the desired contour of the part being molded. A metal face sheet typically requires purchasing a large amount of raw material which is then removed using lengthy machining operations to achieve the final shape of the metal face sheet. What is needed, then, are improved methods and systems for manufacturing a layup mandrel. The present disclosure satisfies this need.

<CIT>, according to its abstract, concerns a tooling assembly is provided, for use with a panel defining a tool-side surface and the tool-side surface defining a profile. The tooling assembly includes a base, a plurality of support members fixedly attached to the base, a plurality of frames, and a securing system. The frames each define an upper surface, where each support member is releasably coupled to a corresponding frame by a fastening system. The upper surfaces of the frames are each shaped to correspond with a portion of the profile of the tool-side surface of the panel. The securing system is for providing a suction force configured to releasably secure the panel against the upper surface of the frames.

<CIT>, according to its abstract, concerns a vacuum bag moulding of carbon-fibre-reinforced-plastics, sheet-form, heat-cured articles net-to-size, with formed edges, accomplished by providing mold periphery elements of corresponding moulding edge profile on the moulding face of moulding tooling, with provision for sliding of periphery elements across the moulding face during curing.

Illustrative, non-exclusive examples of inventive subject matter according to the present disclosure are described in the following paragraphs:
In accordance with one aspect, a layup mandrel, comprising:.

The layup mandrel may have one or more of the following features:
The layup mandrel further comprises a base comprising an assembly jig holding the ribs during assembly of the rib structure. The layup mandrel further comprises a base comprising movable vanes for positioning and holding the ribs during assembly of the rib structure, wherein the base is modular for assembly of different configurations of the ribs.

The layup mandrel further comprises a detachable base comprising one or more handles for transporting or handling the layup mandrel attached to the detachable base.

Still further, the handles comprise one or more openings capable of receiving at least one tool selected from:.

Further, the rib structure comprises tabs forming joints with the detachable base.

Still further, the rib structure comprises or consists essentially of the composite material.

Further, the skin is non-porous so that the skin has vacuum integrity when the skin is sealed to a bagging film so as to form a bag containing the part, the vacuum integrity maintaining a vacuum in the bag used for pressing the part against the skin during curing of the composite material.

Still further, the rib structure comprises a frame supporting the ribs and the frame comprises openings allowing airflow under the skin for increasing heat transfer during the curing.

The part comprises a face sheet and the face sheet is bonded to the surface so that the rib structure comprises an integrated stiffener for the face sheet.

The layup mandrel further comprises a face sheet on the skin, wherein the face sheet has a surface having the curvature of the lofted surface; wherein the curvature molds the part comprising an aircraft part pressed against the face sheet during curing of the part.

The surface comprises a machined surface.

The face sheet includes bushings or locators.

Further, the rib structure comprises a frame supporting the ribs, the ribs comprise faces and edges, the faces comprise cross-sectional surfaces of the rib structure, the edges define the lofted surface, and the skin is disposed on the edges.

Still further, the rib structure comprises a notch holding a block having a block surface including a contour with higher resolution for molding a section of the part.

In another aspect, a method of laying up a face sheet, comprising:.

In one example, the method, further comprises:.

In another example, the method comprises machining a surface of the face sheet using only one machining step to form a machined surface, the pressure pressing the part against the machined surface during the molding.

In one further example, the method comprises cutting a plurality of the ribs from one or more panels comprising the composite material, wherein each of the ribs have one of the faces and one of the edges shaped to form the lofted surface.

In yet another example, the method comprises detaching the base and re-using the base to assemble another one of the layup mandrels.

In the following description, reference is made to the accompanying drawings which form a part hereof, and which is shown, by way of illustration, several embodiments. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present disclosure.

<FIG> illustrates a layup mandrel <NUM> (e.g., rapid tooling layup mandrel) comprising a rib structure <NUM> comprising ribs <NUM> defining a lofted surface <NUM>; a skin <NUM> attached to and supported by the rib structure <NUM>; and a face sheet <NUM> on the skin <NUM>. The face sheet <NUM> has a surface <NUM> having a curvature <NUM> defined by the lofted surface <NUM> so that the mandrel <NUM> shapes a part pressed against the surface <NUM> during curing of the part. In the example of <FIG>, the layup mandrel <NUM> further comprises a base <NUM> comprising an assembly jig <NUM> holding the ribs <NUM> during assembly of the rib structure <NUM>.

<FIG> illustrates the base <NUM> further includes handles <NUM> (e.g., grips or tool handling structures) for handling and lifting the layup mandrel <NUM> attached to the base <NUM>. The handles <NUM> or tool handling structures comprise one or more openings <NUM> capable of receiving at least one tool selected from one or more forklift forks, one or more lifting hooks, or one or more attachments for connecting casters so that the base <NUM> is capable of being at least lifted or transported by the tool (e.g., using a fork lift, a crane, or the casters).

<FIG> further illustrates an example assembly jig <NUM> comprises supports <NUM> (e.g., jigs or vanes <NUM>) wherein the supports <NUM> comprise mounts positioning and holding the ribs <NUM> during the assembly of the rib structure <NUM>. In this way, the base is modular for assembly of different configurations of the ribs <NUM>. The supports <NUM> (e.g., vanes or mounts) run the length of the base <NUM> and have the attach holes <NUM> and/or slots <NUM> for positioning and mounting pieces <NUM>. In one example, the pieces <NUM> that run across the width of the base <NUM> (along the shorter direction) are stiffeners to keep the base <NUM> flat and provide the base <NUM> its structural integrity.

<FIG> illustrate a method of making a layup mandrel and molding a part.

<FIG> illustrates obtaining a base of the correct size to build the layup mandrel. In one or more examples, the base is configured for building or stacking up a plurality of different layup mandrels.

<FIG> illustrates bonding a set of ribs together using the base as an assembly jig, so as to form the set of ribs into a rib structure. In one or more examples, the ribs are made of the same composite material (e.g., carbon fiber, fiberglass) as the part being molded using the layup mandrel.

<FIG> illustrates bonding a skin (e.g., loft skin) to the rib structure, so as to create a shape for the face sheet comprising the layup mandrel tool surface. In one or more examples, the skin is stretched over and then bonded under tension to the rib structure to form a drum-like surface.

In one or more examples, the skin is made of one or more different laminates depending on the application requirements. In one or more examples, the skin comprises one or more materials having full vacuum integrity, allowing the face sheet to be bagged to the loft skin during curing of the face sheet under vacuum conditions. In this way, if using an autoclave, the layup mandrel is in an "equalized" pressure environment and the rib structure is not exposed to the autoclave pressure during curing (eliminating the need to design the rib structure to withstand large pressure differentials without collapse).

Example materials for the skin include, but are not limited to, a material that bonds well to the rib structure and ultimately the face sheet. Example properties of the skin include, but are not limited to, the skin having at least one of a stiffness, durability, and an ability to withstand extreme temperatures, e.g., to match different application requirements. In one or more examples, the stiffness, durability and ability to withstand extreme temperatures are tailored by selection of the one or more different materials and/or thickness of the skin. In yet further examples, the loft skin comprises a mesh enabling three dimensional printing or additive manufacturing of the face sheet.

<FIG> illustrates laying up the face sheet on a surface <NUM> of the skin <NUM>, vacuum bagging the face sheet to the loft skin and then curing the face sheet (e.g., at a temperature in a range from room temperature up to more than <NUM> degrees Celsius) if using an autoclave when the face sheet is vacuum sealed within the bag. In one or more examples, the face sheet comprises a composite material. Example composite materials include, but are not limited to, fiber (e.g., carbon fiber) reinforced epoxy resin (e.g., BMI resin) and thermoplastic. Example face sheet layup methods include, but are not limited to, the face sheet being laid up by hand or using automatic fiber placement. The cured face sheet includes features or functionality used during layup mandrel builds (e.g., scribes, optical tooling points, pad-ups, or drill starts). Examples of optical tooling points include, but are not limited to, a tooling ball (e.g., steel sphere) having a stem that slips into a hole in the layup mandrel and allowing the tooling ball to be probed so as to locate the tooling ball.

Example molding conditions for the face sheet include, but are not limited to, conditions wherein the rib structure and the skin (in combination) mold the face sheet during a curing process.

<FIG> illustrates after curing, optionally machining (e.g., computer numerical control, or CNC milling), finishing, or smoothing the surface of the face sheet (comprising the surface of the layup mandrel) to obtain a final contour shape of the layup mandrel.

<FIG> illustrates using the layup mandrel to produce (mold) the part <NUM> against the face sheet. At this point the use of the base is optional. In one or more examples the base is removed prior to molding the part.

In one or more examples, the curing temperature depends on the material being used for the face sheet and/or part. Example curing temperatures are listed in the table below.

In General, layup mandrel tools are designed to account for stresses resulting from the different coefficient of thermal expansion (CTE) and contraction between different components during high temperature curing. Embodiments described herein fabricate the rib structure, the face sheet, and the part being molded by the layup mandrel with the same materials to ensure CTE compatibility between the layup mandrel and the part. In one or more examples, the skin does not need to be manufactured with the same material as the rib structure, part, or face sheet because the thickness of the skin is so thin that its CTE does not significantly impact the contraction and expansion of the layup mandrel.

<FIG> illustrates an example wherein the ribs <NUM> are slats <NUM> cut from a large stock panel using water jet cutting. To facilitate fast fabrication, each rib <NUM>, including ribs <NUM> having a different shape, have a notch <NUM> for identifying the ordering of the ribs <NUM> during the assembly. The ribs <NUM> comprise faces <NUM> and edges <NUM>, the faces <NUM> comprise cross-sectional surfaces <NUM> of the rib structure, and the edges <NUM> define the lofted surface <NUM>. Each notch <NUM> is inserted into and held in a corresponding slot <NUM> in a rail <NUM> so as to form the rib structure <NUM> comprising a set of ribs <NUM> secured in a frame <NUM>. In one or more examples, the plan (including the shape, dimensions, and nesting) of the ribs <NUM> is generated using a profile automatically generated according to a design required by a customer. Example design methods include, but are not limited to, the plan of each of the ribs being automatically designed using relations in computer aided design (CAD) without coding or scripting.

<FIG> illustrates a set of ribs <NUM> assembled into a rib structure <NUM> creating the lofted surface <NUM> defining a rough shape for the face sheet. The spacing S of the ribs, frequency, and pattern are designed to optimally support the desired curvature and surface profile resolution of the part being molded. In one or more examples, in areas requiring higher contour, the spacing between the ribs is decreased for higher resolution. Example spacings include a spacing S in a range of <NUM>-<NUM> inches.

<FIG> illustrates the rib structure <NUM> permanently bonded to the skin <NUM>, so that after the face sheet is cured on the skin <NUM>, the rib structure <NUM> comprises an integrated stiffener <NUM> for the skin <NUM> and the face sheet.

<FIG> illustrate machining of the face sheet <NUM> along a trajectory <NUM> that consumes any error in the contour of the surface <NUM> of the face sheet <NUM> (as defined or formed by the skin on the rib structure), thereby forming a machined surface <NUM>.

<FIG> illustrate an example rib structure <NUM> including a notch <NUM> comprising an area for holding or mounting a block <NUM> having a block surface <NUM>. The block surface <NUM> comprises a contour <NUM> having more highly detailed area for molding a region of the face sheet with higher resolution. In one or more examples, the block <NUM> (e.g., molding block) comprises a carbon foam or other molded or machined materials.

<FIG> illustrates an example face sheet <NUM> including plies <NUM>, wherein one or more of the plies <NUM> include functionality, e.g., bushings or locators for locating the face sheet during machining operations, or a spot <NUM> for a tool ball used for face sheet or part positioning.

<FIG> illustrate an example wherein the rib structure <NUM> comprises joints <NUM> (e.g., finger joints) comprising tabs <NUM>. The tabs <NUM> comprise holes <NUM> for fasteners <NUM> (e.g., pins or screws), wherein the fasteners <NUM> are used to fasten the rib structure <NUM> to the base <NUM> along the length of the rib structure <NUM> and along a cross-section of the rib structure <NUM>. The rib structure <NUM> further includes curved concave sections <NUM> defining openings <NUM> that increase airflow <NUM> under the rib structure. The airflow <NUM> facilitates heat transfer during the molding process. The curing typically, but not always, requires heating the material to cure temperature. In one or more examples, the cure also generates heat which may need removed. In some examples, the airflow is maintained at cure temperature and transfers heat to or from the part during cure to keep the part at the proper temperature. A cavity <NUM> defined between the rib structure <NUM> and the base <NUM> is used for channeling the airflow <NUM>. In other examples, the cavity <NUM> and concave sections <NUM> are formed entirely in the base <NUM>.

<FIG> illustrate re-purposing a conventional layup mandrel as a base <NUM> for another layup mandrel <NUM> comprising a rib structure <NUM>; the skin; and the face sheet <NUM>.

<FIG> illustrate a layup mandrel <NUM> having a shape configured to mold an aircraft part (e.g., a wing leading edge). The layup mandrel <NUM> comprises a rib structure <NUM> comprising female connectors for connecting to the base <NUM>.

<FIG>, <FIG>, and <FIG> illustrate a system <NUM> and method for molding a part <NUM> using the layup mandrel <NUM>. <FIG> is a perspective view illustrating a bagging film <NUM> on the layup mandrel <NUM>, wherein the bagging film <NUM> is used to seal the part comprising a face sheet <NUM> during curing of the face sheet <NUM>.

<FIG> and <FIG> illustrate the system <NUM> further comprises double sided adhesive <NUM> (e.g., tacky tape), wherein a first side <NUM> of the adhesive <NUM> contacts the skin <NUM> and forms a continuous sealed border or perimeter <NUM> around an entirety of the part <NUM>. The bagging film <NUM> is sealed to a second side <NUM> of the double sided adhesive <NUM> around the whole perimeter <NUM>, so as to form an airtight bag <NUM> comprising the surface <NUM> of the skin <NUM>, the double sided adhesive <NUM>, and the bagging film <NUM>.

<FIG> and <FIG> further illustrate the system <NUM> comprises a vacuum port <NUM> allowing access to a sealed volume of the bag <NUM> while maintaining vacuum integrity of the bag <NUM> during the molding process. The system <NUM> further comprises a vacuum pump <NUM> connected to the vacuum port for sucking air <NUM> from the bag <NUM> via the vacuum port <NUM>, thereby evacuating the bag <NUM> and forming a vacuum <NUM> inside the bag <NUM>. During molding of the part <NUM> placed on the layup mandrel <NUM>, atmospheric pressure <NUM> outside the evacuated bag <NUM> presses on the part <NUM> over an entire surface of the evacuated bag <NUM>, so as to press the part <NUM> against the layup mandrel <NUM> (and molding the part according to contour of the lofted surface <NUM>). In one or more examples, the part <NUM> is pressed against the layup mandrel with a pressure, e.g., in a range from atmospheric pressure to <NUM> pounds per square inch (e.g., <NUM>-<NUM> pounds per square inch). The molding further comprises heating (e.g., at a temperature in a range of room temperature to more than <NUM> degrees Celsius) the part <NUM> so as to cure the part <NUM> while the part <NUM> is being molded using the pressure. In one or more examples, the part or face sheet is molded and cured in an autoclave. However, an autoclave is not necessary. In other examples, the part or face sheet are molded and cured under pressure (e.g., atmospheric pressure), e.g., subjected and applied using the evacuated bag <NUM>.

As described herein, in some examples, the part <NUM> being molded on the layup mandrel <NUM> comprises a face sheet <NUM> bonded to or attached to the skin <NUM> (so that the face sheet is molded against the skin <NUM>). In further examples, after the face sheet is <NUM> molded on the layup mandrel <NUM>, the layup mandrel <NUM> further comprising the face sheet <NUM> is used to mold another part <NUM> using the system <NUM>, so that the part <NUM> is now molded against the surface <NUM> of the face sheet <NUM>. The contour of the surface <NUM>, <NUM> is determined by the predetermined design of the lofted surface <NUM> and optionally also the finished profile of the surface <NUM> of the face sheet <NUM> (e.g., as formed by machining). In one more examples, only one machining operation is used to form or machine the surface <NUM> into the machined surface <NUM> against which the part <NUM> is molded.

<FIG> illustrates a part <NUM> molded using the layup mandrel <NUM>.

<FIG> is a schematic of an aircraft <NUM> comprising parts <NUM> comprising aircraft parts <NUM> manufactured and moldable using the layup mandrel <NUM>. <FIG> illustrates example aircraft parts <NUM> include, but are not limited to, a wing skin <NUM> (including wing leading edge <NUM>), a wing spar <NUM>, a longeron <NUM>, a bulkhead <NUM>, a fuselage section <NUM>, or fuselage skin <NUM>.

<FIG> is a flowchart illustrating a method of laying up a face sheet, comprising the following steps.

Block <NUM> represents obtaining a base comprising an assembly jig.

Claim 1:
A layup mandrel (<NUM>) to mold a part comprising or consisting essentially of a
composite material, the layup mandrel comprising:
a rib structure (<NUM>) comprising ribs (<NUM>) defining a lofted surface (<NUM>); and
a skin (<NUM>) attached to and supported by the rib structure (<NUM>), wherein:
the skin (<NUM>) has a surface (<NUM>) having a curvature (<NUM>) of the lofted surface (<NUM>);
the ribs (<NUM>) are disposed to at least partially shape the curvature (<NUM>) molding said part (<NUM>) pressed against the skin (<NUM>) during curing of the part (<NUM>);
a face sheet (<NUM>) on the skin (<NUM>);
a bagging film sealed to the face sheet so as to form a bag (<NUM>) containing the part, and evacuating the bag (<NUM>) so as to apply the pressure pressing the part against the face sheet, so as to finish molding the part against the face sheet.