Ply location templates for double diaphragm vacuum bagging systems

Systems and methods are provided for securing laminates to mandrels. One embodiment is a method for facilitating layup of preforms, the method including selecting a mandrel that includes at least one receptacle, disposing a first vacuum bag atop the mandrel that covers the receptacle, selecting a Ply Location Template (PLT) that includes a securement element, aligning a portion of the securement element with the receptacle, pressing the portion of the securement element downward into the first vacuum bag and driving the portion of the securement element into the receptacle, and abutting a preform against the PLT.

FIELD

The disclosure relates to the field of composite fabrication, and in particular, to fabrication of composite parts via a vacuum bag.

BACKGROUND

When fabricating a preform into a composite part (e.g., a Carbon Fiber Reinforced Polymer (CFRP) part, a vacuum bag may be placed atop a preform. Evacuation of the air under the vacuum bag allows atmospheric pressure to push the preform down onto a mandrel. Thus, the vacuum bag may press the preform onto a mandrel in a desired shape. The vacuum bag may apply a variety of forces to the preform during curing, and these forces may even shift the location of the preform on the mandrel. Thus, securement of the preform onto the mandrel remains an important consideration. This concern is amplified in scenarios where double diaphragm vacuum bagging is performed. In double diaphragm vacuum bagging, a first vacuum bag is placed between the mandrel and the preform, and a second vacuum bag is placed atop the preform. The vacuum bags have a lower coefficient of friction than the preform itself. Hence, the entire assembly is more vulnerable to sliding across the mandrel during set up and curing. If the preform slides during setup and/or curing, then a shape of a resulting composite part may be out of tolerance, which is undesirable.

SUMMARY

Embodiments described herein provide Ply Location Templates (PLTs) which include specialized mounts for use in double diaphragm bagging. The mounts utilize spherical bearings which penetrate into a mandrel and distort (but do not rip) a vacuum bag underlying the preform. When secured via the mounts, the PLTs physically prevent the preform from shifting or distorting during layup and curing.

One embodiment is a method for facilitating layup of preforms, the method including selecting a mandrel that includes at least one receptacle, disposing a first vacuum bag atop the mandrel that covers the receptacle, selecting a Ply Location Template (PLT) that includes a securement element, aligning a portion of the securement element with the receptacle, pressing the portion of the securement element downward into the first vacuum bag and driving the portion of the securement element into the receptacle, and abutting a preform against the PLT.

A further embodiment is a method for securing a vacuum bag to a mandrel, the method including disposing a vacuum bag atop a mandrel, and securing the vacuum bag to the mandrel.

A further embodiment is a method for placing a preform onto a mandrel, the method including identifying a tool that is at the mandrel and for which translation has been prevented, and abutting an edge of a preform against the tool.

Yet another embodiment is a non-transitory computer readable medium embodying programmed instructions which, when executed by a processor, are operable for performing a method for facilitating layup of preforms that includes: selecting a mandrel that includes at least one receptacle, disposing a first vacuum bag atop the mandrel that covers the receptacle, selecting a Ply Location Template (PLT) that includes a securement element, aligning a portion of the securement element with the receptacle, pressing the portion of the securement element downward into the first vacuum bag and driving the portion of the securement element into the receptacle, and abutting a preform against the PLT.

A still further embodiment is an apparatus in a form of a Ply Location Template (PLT), including: a body that conforms with a surface of a mandrel; and at least one mount comprising, a socket, a securement element disposed within the socket having a portion that protrudes beneath the socket, and a biasing component within the socket that applies force which pushes the portion out of the socket.

An even further embodiment is a method for placing a template on a mandrel, the method including selecting a template that includes a body and at least one mount comprising a securement element disposed within the body, and aligning the body at a mandrel to secure the template to the mandrel.

Other illustrative embodiments (e.g., methods and computer-readable media relating to the foregoing embodiments) may be described below. The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings.

DESCRIPTION

The figures and the following description illustrate specific illustrative embodiments of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the disclosure and are included within the scope of the disclosure. Furthermore, any examples described herein are intended to aid in understanding the principles of the disclosure, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the disclosure is not limited to the specific embodiments or examples described below, but by the claims and their equivalents.

Composite parts, such as Carbon Fiber Reinforced Polymer (CFRP) parts, are initially laid-up in multiple layers that together form a laminate. Individual fibers within each layer of the laminate are aligned parallel with each other, but different layers may exhibit different fiber orientations in order to increase the strength of the resulting composite along different dimensions. The laminate may include a liquid resin that solidifies in order to harden the laminate into a composite part (e.g., for use in an aircraft). Carbon fiber that has been impregnated with an uncured thermoset resin or a thermoplastic resin is referred to as “prepreg.” Other types of carbon fiber include “dry fiber” which has not been impregnated with thermoset resin but may include a tackifier or binder. Dry fiber may be infused with resin prior to curing. For thermoset resins, the hardening is a one-way process referred to as curing, while for thermoplastic resins, the resin may return to liquid form if it is re-heated. The following discussion in the specification describes enhanced systems that facilitate layup and processing of composite parts.

FIGS. 1-3illustrate setup processes for a system that cures a preform via double diaphragm vacuum bagging techniques. Specifically,FIG. 1is a diagram of a composite fabrication system100that includes a mandrel110, a first vacuum bag120, and Ply Location Templates (e.g., PLTs122-128) for fabricating a composite part in an illustrative embodiment. According toFIG. 1, a surface112of mandrel110will receive a preform at region118. First vacuum bag120, which is transparent, is laid-up atop and sealed to surface112(including region118), and PLTs122-128are placed atop first vacuum bag120and secured to mandrel110. PLTs122-128include borders140, which help to define boundaries (e.g., corner radii) for a preform that will be laid-up in region118.

Mandrel110includes hollow portions114, which are connected via slits116with vacuum cable130. When a vacuum is applied via vacuum cable130, air is evacuated from hollow portions114via slits116. This action will draw first vacuum bag120into hollow portions114, which shapes a preform atop first vacuum bag120into a desired shape.

FIG. 2illustrates the system ofFIG. 1wherein a preform200has been laid-up in region118. In this embodiment, flanges210of preform200protrude out over hollow portions114, but are supported by first vacuum bag120. These flanges210will be drawn into hollow portions114when a vacuum is applied. Features220(e.g., corners, edges, sides) of preform200are supported by PLTs122-128, and hence will remain in place when vacuum is drawn.

FIG. 3illustrates the system ofFIG. 2, wherein a second vacuum bag300, which is also transparent, has been laid-up atop preform200, PLTs122-128, first vacuum bag120, and mandrel110. Second vacuum bag300has been sealed to mandrel110. A first vacuum may then pull air from between first vacuum bag120, and second vacuum bag300. Furthermore, as shown inFIG. 3, a second vacuum is drawn to pull air out of hollow portions114via vacuum cable130in direction310. This applies suction which physically stretches and deforms the first vacuum bag120and second vacuum bag300, drawing both into hollow portions114. The deformation of the vacuum bags also bends flanges210as indicated by arrows320, which gives preform200a desired shape for curing. During this process, PLTs122-128provide structural support that prevents features220from distorting, warping, shifting, or tearing.

With an explanation provided of the general operations of composite fabrication system100during curing,FIGS. 4-6further illustrate PLTs in illustrative embodiments. Specifically,FIGS. 4-6are top views of PLT122, PLT124, and PLT128, respectively. PLT126shares a similar two-prong design with PLT122. As shown inFIG. 4, PLT122includes body420, which is substantially flat or otherwise conforms with surface112of mandrel110. One or more prongs410protrude from body420, and prongs410may include borders140that define a corner, side, or other feature of preform200. Contour430at PLT122skirts around a hollow portion114at mandrel110. Furthermore, mounts440retain PLT122in position at mandrel110, even when PLT is placed atop the first vacuum bag120.FIGS. 5-6illustrate similar features for PLTs126-128.

FIGS. 7-8illustrate mounting features for the PLTs ofFIGS. 4-6. Specifically,FIG. 7is an exploded perspective view of region7ofFIG. 2which illustrates how mounts440ofFIG. 4hold PLT122in position at mandrel110.FIG. 7illustrates that PLT122includes multiple sockets724, which are aligned with receptacles752in mandrel110as indicated by axes710. Each mount440includes a securement element716(e.g., a spherical ball) within socket724. Securement elements716each include a portion that protrudes downward from a socket724, forming indent742in first vacuum bag120and protruding into receptacles752. When a portion of securement element716protrudes downwards into a receptacle752, the portion physically interferes with motion of PLT122along surface112, which locks the PLT122in position along surface112of mandrel110. Mounts440also include biasing devices714(e.g., a rubber gasket, a helical spring, etc.) which applies force that pushes securement element716downwards. In one embodiment, securement elements716are magnetic, and hence biasing devices714comprise magnetic portions of securement elements716. In such an embodiment, biasing devices714may be integral with and/or indistinguishable from securement elements716. Caps712hold biasing devices714in place, and caps712are mounted via fasteners732to holes722in PLT122. Furthermore, in embodiments where mandrel110is magnetic (e.g., made of steel, invar, etc.), a magnet760(e.g., a rare earth magnet) magnetically drives PLT122into mandrel110(e.g., because mandrel110or a portion thereof is magnetic). This action magnetically drives securement element716into receptacle752. In a further embodiment, securement element716is itself magnetic.

FIG. 8is a section cut side view of PLT122mounted to a mandrel110in an illustrative embodiment, and corresponds with view arrows8ofFIG. 7.FIG. 8illustrates that each securement element716protrudes at least partially downward out of a socket724and into a receptacle752. Biasing devices714are placed within recesses810defined by caps712, and biasing devices714push securement element716into place.

FIG. 9is a zoomed in section cut side view of PLT122mounted to a mandrel110in an illustrative embodiment.FIG. 9illustrates further features, such as portion910of securement element716, which protrudes beneath socket724.FIG. 9also illustrates prongs920of socket724. Prongs920reduce a diameter of socket724in order to prevent securement element716from falling downwards out of socket724. Specifically, while a portion of socket724and securement element716generally have a diameter D1, prongs920reduce the diameter of another portion of socket724to D2, which is less than D1. This aspect physically prevents securement element716from exiting its socket724. Socket752has a diameter D3which is smaller than D1, and smaller than or equal to D2.

Illustrative details of the operation of composite fabrication system100will be discussed with regard toFIG. 10. Assume, for this embodiment, that a technician wishes to perform double-diaphragm vacuum bagging in order to fabricate a composite part at mandrel110.

FIG. 10is a flowchart illustrating a method1000for fabricating a composite part in an illustrative embodiment. The steps of method1000are described with reference to composite fabrication system100ofFIG. 1, but those skilled in the art will appreciate that method1000may be performed in other systems. The steps of the flowcharts described herein are not all inclusive and may include other steps not shown. The steps described herein may also be performed in an alternative order.

In step1002, a technician selects mandrel110, which includes a receptacle752. A first vacuum bag120is disposed atop the mandrel110(e.g., by the technician, or a robot) and covers the receptacle752(step1004). A PLT122is selected in step1006. The PLT122includes a socket724, as well as a securement element716within the socket724. The securement element716has a portion910that protrudes beneath the socket. The portion910of the securement element716is aligned with the receptacle752(e.g., by rolling securement element716within socket724as PLT122traverses the surface112of mandrel110) (step1008). The method further includes pressing portion910downward to indent the first vacuum bag120and drive the portion910into the receptacle752(step1010). This step may be performed manually, or may be performed by placing a magnet at PLT122which magnetically forces PLT122towards surface112of mandrel110. With portion910pressed into receptacle752, physical interference prevents translation of the PLT122.

A preform200may be laid-up atop first vacuum bag120, and features220of the preform200may contact the borders140of PLT122(and any other PLTs that have been secured). That is, preform200may be abutted against PLT122(step1012), in response to identifying a tool (e.g. PLT122) that is at the mandrel for which translation has been prevented (e.g., that has been secured to the mandrel). A second vacuum bag300may then be placed atop the preform200and the PLT122, and the vacuum may draw flanges210of preform200into hollow portions114of mandrel110. Heat and/or pressure may then be applied to cure the preform200into a composite part.

Method1000provides a benefit over prior techniques because it enables preforms to be secured relative to a mandrel, even when the preforms are laid-up atop a vacuum bag which may be slippery or slick. Hence, motion and/or distortion of preforms during the curing process is prevented, which increases the efficacy of double-diaphragm curing processes.

EXAMPLES

In the following examples, additional processes, systems, and methods are described in the context of a double diaphragm vacuum bagging system and composite fabrication process.

FIG. 11is a block diagram of a composite fabrication system1100in an illustrative embodiment. Composite fabrication system1100includes mandrel1110having surface1112and hollow portion1114. Hollow portion1114includes slits1116. Air evacuates from hollow portion1114via slits1116and out via vacuum cable1118. Mandrel1110also includes receptacles1152. First vacuum bag1120is laid-up atop surface1112, and PLTs1122and1124are placed atop the first vacuum bag1120. Specifically, a securement element1156within a socket1154of each PLT is aligned with a receptacle1152. Biasing devices1158push securement elements1156downward, and a portion1159of securement elements1156protrudes downward out of socket1154. Magnets1180provide force that drives the PLTs into the receptacles1152. Furthermore, each securement element1156is held within socket1154by a combination of fasteners1172and cap1170.

Preform1160includes features1164which contact borders1140of PLT1122and PLT1124. Second vacuum bag1190is placed atop the PLTs and the preform, in order to form a double-diaphragm seal in which to cure preform1160. Specifically, a first diaphragm1192is formed between first vacuum bag1120and mandrel1110, and a second diaphragm1194is formed between second vacuum bag1190and first vacuum bag1120.

FIG. 12is a flowchart illustrating a method1200of operating a PLT in an illustrative embodiment. According to method1200, step1202includes selecting a PLT that includes a body and at least one mount comprising a socket and a securement element disposed within the socket. Step1204includes aligning the socket at a mandrel to secure the PLT to the mandrel.

Referring more particularly to the drawings, embodiments of the disclosure may be described in the context of aircraft manufacturing and service in method1300as shown inFIG. 13and an aircraft1302as shown inFIG. 14. During pre-production, method1300may include specification and design1304of the aircraft1302and material procurement1306. During production, component and subassembly manufacturing1308and system integration1310of the aircraft1302takes place. Thereafter, the aircraft1302may go through certification and delivery1312in order to be placed in service1314. While in service by a customer, the aircraft1302is scheduled for routine work in maintenance and service1316(which may also include modification, reconfiguration, refurbishment, and so on). Apparatus and methods embodied herein may be employed during any one or more suitable stages of the production and service described in method1300(e.g., specification and design1304, material procurement1306, component and subassembly manufacturing1308, system integration1310, certification and delivery1312, service1314, maintenance and service1316) and/or any suitable component of aircraft1302(e.g., airframe1318, systems1320, interior1322, propulsion system1324, electrical system1326, hydraulic system1328, environmental1330).

As shown inFIG. 14, the aircraft1302produced by method1300may include an airframe1318with a plurality of systems1320and an interior1322. Examples of systems1320include one or more of a propulsion system1324, an electrical system1326, a hydraulic system1328, and an environmental system1330. Any number of other systems may be included. Although an aerospace example is shown, the principles of the invention may be applied to other industries, such as the automotive industry.

As already mentioned above, apparatus and methods embodied herein may be employed during any one or more of the stages of the production and service described in method1300. For example, components or subassemblies corresponding to component and subassembly manufacturing1308may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft1302is in service. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the subassembly manufacturing1308and system integration1310, for example, by substantially expediting assembly of or reducing the cost of an aircraft1302. Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft1302is in service, for example and without limitation during the maintenance and service1316. For example, the techniques and systems described herein may be used for material procurement1306, component and subassembly manufacturing1308, system integration1310, service1314, and/or maintenance and service1316, and/or may be used for airframe1318and/or interior1322. These techniques and systems may even be utilized for systems1320, including, for example, propulsion system1324, electrical system1326, hydraulic1328, and/or environmental system1330.

In one embodiment, a part comprises a portion of airframe1318, and is manufactured during component and subassembly manufacturing1308. The part may then be assembled into an aircraft in system integration1310, and then be utilized in service1314until wear renders the part unusable. Then, in maintenance and service1316, the part may be discarded and replaced with a newly manufactured part. Inventive components and methods may be utilized throughout component and subassembly manufacturing1308in order to manufacture new parts.