Patent Application
20070108646
Not Applicable
Not Applicable
The present invention relates to a method of fabricating a composite part having integral structural details.
Fiber composite parts may be generally formed into a wide variety of shapes. For example, composite fibers may be shaped as a fairing. However, due to fiber composite parts being generally more flexible in bending and less stiff compared to steel or aluminum, the solid laminate fairing fabricated of composite fibers may not be capable of withstanding high wind gusts thereby deforming the fiber composite fairing while the airplane is in motion. Wind gusts may buckle and stress the fiber composite fairing thereby ultimately possibly destroying the fiber composite fairing. As such, solid laminate fiber composite parts may have limited applicability to highly stressed conditions where the structure is subjected to bending loads.
Stiffeners may be incorporated into the fiber composite fairing to increase the stiffness of the fairing for withstanding the air gust and air pressures applied to the fairing as the airplane flies through the air. However, manufacturers of fiber composite parts have been unsuccessful in incorporating stiffeners into fairings in a cost efficient manner. Moreover, manufacturers of fiber composite parts have been unsuccessful in reliably incorporating stiffeners into an airplane fairing in a unitized fashion. One reason is that the resin may not flow through the fiber completely prior to resin cure thereby leaving dry areas of fiber. Another reason is that pooling of resin may occur as resin flows through the fiber. The state of the art requires that the stiffeners be fabricated separately and subsequently joined or assembled to the parent molded surface.
Accordingly, there is a need in the art for an improved method of fabricating a fiber composite part which incorporates structural details in a single unitized structure.
The present invention addresses the needs discussed above and discussed herein as well as those that are known in the art. As will be discussed in detail below, a method of fabricating a part with integral structural details will be discussed in relation to a fairing with stiffeners. However, the example (i.e., fairing with stiffeners) used to describe the method is not meant to limit the scope of this disclosure. Accordingly, it is contemplated that the description of the method may be variously embodied and employed to other types of parts such as trusses with integral structural details.
A fairing may define a control surface. The control surface may have a smooth curved configuration bounded by an upper horizontal edge, opposed curvilinear lateral edges, and a lower arc shaped interface which mates with an adjacent part of an assembly. On a rear side of the fairing, a plurality of horizontal and vertical stiffeners may be formed behind the control surface to stiffen the control surface.
The control surface may be formed by laying fiber on a molding surface of a tool mold. The molding surface may have a corresponding negative configuration of the control surface of the fairing. The tool mold may also have other surfaces for defining the upper horizontal edge, lateral opposed edges and the lower arc shaped interface.
The stiffeners may be fabricated by wrapping a plurality of detail molds, assembling the wrapped detail molds onto the molding surface, flowing resin through the fiber and curing the fiber. In particular, an interface surface and a detail surface of the detail mold may be wrapped with fiber. A top surface of the detail mold may be absent fiber such that the detail mold may be removed from the assembly after the resin has flowed through the fiber and the composite part is cured. The detail molds may be collectively assembled onto the tool mold in a jig saw configuration. Fibers laid on detail surfaces of adjacent detail molds may collectively form the stiffeners along the adjacent boundaries.
The fibers laid on the detail mold may be engaged to the detail mold via vacuum bagging. A plurality of detail molds wrapped with fiber may be inserted into a first vacuum bag. A continuous cloth material may be laid over each of the detail molds, and more particularly, the fiber wrapped about the detail molds. The cloth may also extend continuously to an output port of the first vacuum bag. The first vacuum bag may be sealed and a vacuum applied to the vacuum port. Air may be evacuated out of the first vacuum bag, and the first vacuum bag may apply pressure uniformly onto the fiber so as to compress the fiber onto the detail mold. After sufficient time has elapsed, the detail molds are removed from the first vacuum bag and assembled on the tool mold in the jig saw configuration.
The detail molds and the tool mold may be enclosed in a second vacuum bag. The second vacuum bag may have a plurality of resin input ports and at least one resin output port to flow resin through the fiber wrapped about the detail molds and fiber laid on the tool mold.
The second vacuum bag may be connected to a manifold and a resin reservoir via the resin input port. Also, the second vacuum bag may be connected to a vacuum pump via the resin output port. To flow resin through the fiber, the vacuum pump may be activated thereby evacuating the air from the vacuum bag. Resin may be drawn from the resin reservoir to the manifold. The manifold distributes the resin to the resin input ports of the second vacuum bag. Resin flows through the fibers wrapped on the detail molds and fibers laid on the tool mold. The resin is evacuated from the second vacuum bag via the resin output port(s) of the second vacuum bag. The resin drawn from the second vacuum bag may be collected in resin reservoirs. Since the resin is drawn into the second vacuum bag through the plurality of resin input ports, the resin flows uniformly throughout the fibers wrapped about the detail molds and the fibers laid on the tool mold. The reason is that flow of resin through the fiber is managed in smaller controllable portions.
The resin also flows uniformly through each of the detail molds via a system of resin input and resin channels formed integrally with each of the detail molds. The resin input may be formed at a central location of a top surface of the detail mold. The resin input may be a circular aperture which extends through the detail mold from the top surface to a bottom surface of the detail mold. The resin input may be in fluid communication with a plurality of resin channels integrally formed on the bottom surface of the detail mold. The plurality of resin channels may have a star burst configuration to promote a uniform flow front of resin toward the fibers laid on the interface surface of the detail mold. When resin flows through the second vacuum bag, resin flows through the resin input and through the resin channels. When the resin reaches the distal end of the resin channel, a back pressure is created to force or promote the resin flow front to reach the fiber uniformly. The resin flow front reaches the inner periphery of the fiber laid on the interface surface uniformly thereby promoting a resin flow through all of the fiber.
In another aspect of the method, a manifold may be placed on top of the assembled detail molds. A bottom surface of the manifold may have a mating configuration with the aggregate of top surfaces of the detail molds. The manifold bottom surface may have a system of resin channels that connect a resin input of the manifold to the resin inputs of the detail molds. When the manifold is laid on the top surfaces of the detail molds, a resin conduit is formed. The detail molds, tool mold and the manifold may be inserted into a second vacuum bag with a manifold resin input alignable to a resin input port of the second vacuum bag. Resin may be flowed through the resin input port through the manifold resin input which distributes the resin to the plurality of resin inputs of the plurality of detail molds. The second vacuum bag may also have an output port for drawing excess resin out of the second vacuum bag.
In another aspect of the method, a manufacturing output rate of a composite fiber part manufacturer may be increased with the method disclosed herein. The reason is that the method divides the labor required to build or fabricate the part into a plurality of more separate and manageable parts. For example, a first employee may wrap fiber about a first detail mold, a second employee may wrap fiber about a second detail mold, and a third employee may lay fiber on the tool mold.
The method discussed herein for fabricating the part with the detail has the following advantages. First, resin is distributed to a plurality of input ports and detail molds. This provides control of resin flow on smaller more manageable areas increasing the likelihood that the fiber is flowed with resin and pooling is less likely. This distributed flow of resin also reduces the rate of exotherm associated with the overall volume of resin, to allow for a longer infusion time prior to gelling of the resin and also enabling larger parts to be fabricated The method discussed herein may be referred to as affordable feature integration. Affordable feature integration facilitates parallel production flow resulting in faster throughput, reduced turn around times and reduced costs. Additionally, the manifold which distributes the resin into the plurality of resin input of the detail molds is configurable to fit any configuration of resin inputs. The detail molds may also be located on the tool mold using a third plate located by an external datum. Furthermore, this location of the detail molds provides precise positioning of the details thereby establishing control of the external surfaces of the part and “detolerancing” the internal location of the fiber layers.
These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which:
Referring now to
Referring now to
Fibrous material 24 may be laid on the molding surface 22 of the tool mold 20. The fibrous material 24 may be provided in a sheet form and cut to size to fit the molding surface 22 of the tool mold 20. Additionally, a curved lower portion 26 (see
Referring to
In another example, as shown in
Referring now to
Resin may be flowed through the fibrous material 24 wrapped on the detail mold 32 and laid on the tool mold 20 and co-cured together to form the fairing 10 with stiffeners 14. In particular, the tool mold 20 and the detail molds 32 may be placed or inserted into a second vacuum bag 56, as shown in
More particularly, the second vacuum bag 56 may be laid on an outer periphery 64 of the tool mold 20, as shown in
In the alternative, as shown in
The manifold 84 may also serve the purpose of locating the detail molds 32 with respect to the tool mold 20. In particular, if the detail molds 32 are merely laid on top of the molding surface 22 of the tool mold 20, the location of the detail molds 32 may be considerably varied based on a contention that the detail molds 32 are designed to have some space therebetween when they 32 are disposed on the tool mold 20 in the jig saw configuration. To more accurately locate the detail molds 32 with respect to the tool mold 20, as shown in
In another aspect of the method disclosed herein, the method of fabricating a part having a detail enables a business to divide the labor of fabricating the part having the detail. The method permits a plurality of employees to work on respective detail molds 32 and tool mold 20. In particular, as discussed above, there may be a plurality of detail molds 32 and a tool mold 20 which may be wrapped and laid with fibrous material 24 and assembled together, flowed with resin 62, and co-cured to produce a part having a detail. Advantageously, each of the detail molds 32 may be worked on by different employees, and also, the tool mold 20 may be worked on by a different employee than those working on the detail molds 32. As such, a plurality of employees may work on a single part having details thereby dividing the labor to fabricate the part having the detail. For example, if the part having the detail requires four detail molds 32 and one tool mold 20, and each detail mold 32 requires one man hour to finish and the tool mold 20 requires two man hours, then the total number of man hours required to fabricate the part would be six man hours. Accordingly, a business having one employee working on the detail molds 32 and the tool mold 20 of the part may fabricate one part every six hours. Advantageously, with the method discussed above in fabricating the part having the detail, the business may have three employees working on the detail molds 32 and the tool mold 20. Two employees may each work on two of the detail molds 32 thereby completing the work required on four detail molds 32 in two hours. The third employee may work on the tool mold 20 and complete work on the tool mold 20 in two hours. Accordingly, the business may fabricate one part having the details every two hours. By this simple illustration, the output of the business may be increased threefold.
The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.
