Abstract:
A three dimensional computer aided design (CAD) model of a composite part which includes a plurality of plies including tool side ply(s), and bag side ply(s) is provided. The composite part is formed on a tool. The model includes a first CAD native surface representative of the shape of the tool, a second CAD native shape representative of an excess ply material and made from the first shape, and a third CAD native shape representative of the bag side ply(s) and adjacent to the joined first and second shapes. In particular, the CAD native shapes used to represent the ply(s) may be trims of a surface.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to the modeling of products with CAD (Computer Aided Design) software, and more particularly to the 3-D modeling of composite structures.  
       BACKGROUND OF THE INVENTION  
       [0002]     Large product development projects require the sharing of product design information among many diverse team members. These team members include prime contractor management, engineers, designers, and manufacturing personnel. Additionally, one or more subcontractors may require access to the design information.  
         [0003]     Development of the product may occur in many different locations. For instance, the top-level design may be performed at the prime contractor&#39;s facility with the various lower level parts of the product being designed at the subcontractors&#39; facilities. Moreover, manufacturing of the lower level parts may occur at another location with top-level assembly occurring at yet another location. At any of these locations, project personnel may require access to design information to perform their duties.  
         [0004]     The assembled product may be shipped to another location for testing after which it is sold and placed in operation. Highly mobile products, such as aircraft, may additionally operate over large regions, throughout which operations, maintenance, and repair activity may necessitate instantaneous access to design information. Since customers and operational experience may provide feedback to the design team, the term “development” herein includes all phases of a product&#39;s life. Thus, it has long been felt necessary to provide access to design information at many independent locations that may be separated by significant distances.  
         [0005]     Hindering the ability to share design information, many supplementary or task specific CAD applications incorporate proprietary data structures that may only be accessed via expensive licenses. Thus, only those project personnel with licensed copies of the supplemental CAD application may access the design information. In the alternative, applications have become available which are known as low-end viewers. Low-end viewers enable personnel to access design information stored in a format native to a foundation CAD product. Advantageously, low end viewers are less expensive to license and buy than design type products and are compatible with personal computers which are much less expensive than the CAD workstations which would otherwise be required for design access.  
         [0006]     However, the presence of the proprietary data structures hides certain design information from low-end viewers. Worse yet, some of the proprietary data structures used by supplemental CAD packages specifically relate to the design information of composite parts.  
         [0007]     Since commercial requirements are increasingly demanding the use of composite parts, the use of these proprietary data structures hinders the development of many commercially lucrative products. Accordingly, it would be desirable to provide tools and methods to develop composite parts with CAD applications while allowing low-end viewers at any project location full access to design information regarding the composite part.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention is directed toward a method of representing a composite part in three dimensions with a format that is native to the foundation computer aided design (CAD) applications. CAD native geometric manipulation is used to form a surface representative of the tool on which the composite part will be formed. Other CAD native surfaces or sheet solids are used to represent the plies that make up layers of the composite part.  
         [0009]     In preferred embodiments of the present invention, properties may be associated directly with a surface representing a particular ply or within the same “collector” construct used for the particular CAD package. These associated properties may represent attributes such as the material or orientation of the ply. Additionally, the model may include stacking order constructs to define the relative positioning of composite components such as plies and core. Likewise, design intent, such as parametric constraints and history, may be included in the model.  
         [0010]     The features, functions, and advantages can be achieved independently in various embodiments of the present inventions or may be combined in yet other embodiments. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0012]      FIG. 1  is a schematic view of a computer network within which the present invention may be used.  
         [0013]      FIG. 2  is a flowchart of a method in accordance with a preferred embodiment of the present invention.  
         [0014]      FIG. 3  is a perspective view of a composite part being modeled in accordance with the method of  FIG. 2 .  
         [0015]      FIG. 4  is a partial view of a drawing of a part modeled in accordance with a preferred embodiment of the present invention.  
         [0016]      FIG. 5  is the organization of the model of  FIG. 4 .  
         [0017]      FIG. 6  is a detailed view of  FIG. 5 .  
         [0018]      FIG. 7  is a detailed view of  FIG. 5 .  
         [0019]      FIG. 8  is a detailed view of  FIG. 5 .  
         [0020]      FIG. 9  is a detailed view of  FIG. 5 .  
         [0021]      FIG. 10  is a detailed view of  FIG. 5 .  
         [0022]      FIG. 11  is a pictorial view of the model of  FIG. 4 .  
         [0023]      FIG. 12  is a pictorial view of information in the model of  FIG. 4 .  
         [0024]      FIG. 13  is a pictorial view of an incomplete model associated with a previous design process. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0026]     Previously, wire frame CAD technology allowed modeling of only the edges of the part being modeled. Wire frame models offered no tools for designing, visualizing or otherwise developing, the surfaces or interior volume of parts. With the advent of surface modeling CAD applications, tools became available to create designs that are more explicit.  
         [0027]     Furthermore, with explicit representations, design reviewers who are neither CAD proficient nor technical may fully participate in reviewing the design. Previously, their inability to visualize the part from the limited two-dimensional drawings available prevented them from forming their opinions regarding the design. Thus, three-dimensional surface and solid modeling generally improves the quality of a design and correspondingly reduces development costs.  
         [0028]     Moreover, because composites offer great flexibility in shaping complex parts subject to demanding service environments, providing tools to completely model composite parts is highly desired. Likewise, because manufacturing composite parts entails significant expenditures, improving the manufacturability of the design of composite parts is also desirable.  
         [0029]     Accordingly, the present invention provides a data structure with which to model composite plies that may be used in conjunction with other modeling techniques in order to express the design intent. Since the present invention accomplishes this without the use of proprietary data structures hidden from low-end viewers, manufacturing personnel at remote sites may also access designs modeled in accordance with the present invention.  
         [0030]     In describing the present invention, several definitions will aid in the understanding of the present invention. These definitions will be set forth here at the beginning of the description of the invention.  
         [0031]     First, a model is a mathematical representation of a part. The model may be of a single part, a component of the part, or even a higher-level assembly. Models are usually created with the aid of a CAD software package and are stored as computer files. Many different file formats are available. For instance, CATIA (available from IBM of White Plains, N.Y.) and Unigraphics (available from EDS of Plano, Tex.) represent a few of the many CAD packages available.  
         [0032]     Design intent includes information important to the design but not necessarily embodied in the model. For instance, a design requirement for two surfaces to remain parallel would not necessarily be included in the design geometry. Though, the fact that the two surfaces are parallel could be readily observed. However, if during the course of the design the length of one of the members connecting the two surfaces were to change, the surfaces might skew from being parallel. Thus, without the capture of this piece of design intent, errors might occur.  
         [0033]     Also useful for an understanding of the present invention, the environment in which the present invention may be used merits some attention. The present invention will generally be used by a far-flung product development team as illustrated in  FIG. 1 . For instance, a prime contractor  10  at one location will contract with a specialty subcontractor  12  to aid in the development of the product. Between the prime contractor  10  and the subcontractor  12  a computer connection may be establish via the internet  14  or other computer network. The computer connection  14  allows devices on the prime contractor&#39;s intranet  16  to communicate with devices on the subcontractor&#39;s intranet  18 .  
         [0034]     At the prime contractor&#39;s location, an assembly model  20  may be stored on a mass storage device  22 . Designers working on the model  20  on CAD stations  24  and  26  access the model via the intranet  16 . Per the CAD application licensing agreement, the CAD terminals have licenses  31  to use the CAD application. In contrast, a personal computer  28  at the prime contractor&#39;s location may not have a license  23 . Instead, the personal computer has a low-end viewer  30 . On the personal computer  28  other development team members may view the model via the low-end viewer  30 .  
         [0035]     A similar system exists at the sub contractor&#39;s  12  location using work station  32  with license  33 ; personal computer  34  with low end viewer  36 ; mass storage device  38  storing model  40 ; and an intranet  18  to allow communication between these devices. The primary difference between the model  20  and the model  40  is that the model  20  is typically a higher-level assembly model, whereas the model  40  is a model of a detail part. Of course, the model  40  could be the assembly model and model  20  could be the detail model. Indeed, taken together the two models are an integrated model of the entire product. Also, either model may include models of composite parts. Regardless of the choice of which model is the assembly, a team member at any of the devices may obtain detailed design information regarding even the composite part(s) from the models  20  and  40 .  
         [0036]     Turning now to  FIGS. 2 and 3 , a flowchart depicting a design method  41  for composite parts, in accordance with a preferred embodiment of the present invention, is illustrated along with a generic composite part being modeled. Within an available CAD application the designer models the overall part surface  68  for the composite part as in operation  42 . Then the designer extracts a tool surface  69  in operation  44  Next, as desired, the designer adds excess to the tool surface (not shown) to the model  66 . See operation  46 . The excess surface is desirable to ensure that the laminate ply (to be subsequently modeled) has excess material for manufacturing convenience. A stacking order for the plies in the composite part is assumed to be available in operation  47 ; this stack lists the number, material, and orientation of each ply.  
         [0037]     Using the tool surface  69  as a starting point, the designer then represents the tool side laminate as a surface trimmed from the tool surface  69  as shown in operations  50  and  52 . If necessary, changes (such as adding a cut out  72 ) may be made to the trimmed surface  70  to represent the first tool side ply. Typically, though, the shape of the first bag side ply surface will closely resemble the shape of the tool surface  69  because the tool typically defines the first ply. However, subsequent ply surfaces  74  will typically change incrementally as more features  76  are modeled ply layer-by-ply layer. Properties may also be associated with the surface to, for example, represent the material or orientation selected for the current ply. Colors, names, and other visualization and interrogation aids may also be added. See operation  54 . The designer repeats the operations from operation  50  to  54  for each subsequent bag side ply in operation  56 .  
         [0038]     With the tool side laminate now completely modeled, the designer creates a surface in operation  59  that represents the top of the final tool side ply. Stiffening elements such as honeycomb core can then be modeled as CAD solid elements upon this surface. See operation  60 . The designer can then extract the surfaces of the core that are not common to the “toolside top surface”—these are typically “ramps” and “top” surfaces as in operation  61 . Next, in operation  62 , the ramp and top surfaces can then be combined with the “toolside top surface” to form a “bagside surface”, to enable representation of plies that lay-up over the top of the stiffening (core) element.  
         [0039]     The modeling of the bag side reflects operations similar to those in operations  50  through  58 , as repeated in operation  63 . Once the model  66  is complete, any development team member may then access the detailed design information embodied in the model  66  using a low-end viewer ( 30  or  36  in  FIG. 1 ) as in operation  64 . Moreover, the composite part model  66  may be added to, or created in, a higher-level assembly model at any development location.  
         [0040]     Having described a method  41  in accordance with the present invention, the data structure of the resulting composite part model  66  may be explored. Turning now to  FIG. 4 a  pictorial view may be seen of a typical aircraft section design  80 , which was used to prove the foregoing composite design method  41 . In this example, the section  80  is a Fan Cowl for a Boeing  777  aircraft. The section  80  includes one or more composite parts  82  which lightens and strengthens the section, thereby improving the performance and efficiency of the Boeing  777 . For reference purposes, the composite member  82  has a bag side  84  and a tool side  86 .  
         [0041]      FIG. 5  shows a specification tree  88  for a model  94  (see  FIG. 6  to  12 ) of the aircraft section  80 . At the topmost level, the directory  90 , where the CAD application stores the design file is illustrated. As the designer begins to model the section  80  he creates a rosette  92  (see  FIG. 6  also) in the axis systems collector  93 . The rosette  92  defines the 0 to 90 degree orientation of the plies of the composite parts in the aircraft section  80 . In conjunction with the xy, yz, and zx planes, the rosette  92  defines a coordinate space used by the designer to locate the various features of the model  94 .  
         [0042]     For purposes of proving the method  41  ( FIG. 2 ), a single stiffening element (core)  100  of the composite part was modeled and filed in the core definition collector. In practice, the core models  102  (as shown in  FIG. 7 ) would contain separate solids for each piece and type of material desired for a given core. Here, the core model  102  includes ramps  104  (20 and 30 degree ramps were both included), cutouts  106 , and surface transitions  108 . Though, protrusions and other features could have been included without departing from the spirit and scope of the present invention.  
         [0043]     While a core model  102  was used to prove the method, the present invention is not restricted to composite designs with core. Rather, any laminate composite may be modeled as taught herein without departing from the spirit or scope of the present invention  
         [0044]     Once the core model  102  was completed and verified to be a closed body, the core upper surfaces were extracted from the core model  102 . Next, they were was joined with the toolside top surface. By duplicating the joined surface and (as desired) modifying the duplicated surface the bag side ply surface was created. Then the bag side ply surface was trimmed and modified in turn to create each bag side ply representation and so forth.  
         [0045]     Proceeding down the tree structure  88  of  FIG. 5 , the lines  114 , planes  116 , and points  118  collectors contain construction or support geometry open bodies. These collectors pertain to the present invention in that they contain entities used to define the shells representing the plies.  
         [0046]     Within the tool  120  and bag  124  side sequence collectors of  FIGS. 5 and 9 , the sequences may be found which represent layers in the laminate and which contain the ply definitions. It will be understood by those skilled in the art that the sequences contain ply definitions, and that each ply definition contains a trimmed surface. Therefore, each sequence and ply definition is a CAD “collector”, with the ply geometry being represented by a trimmed surface contained within the ply collector. Again, because the tool side sequence collector  120  resembles the bag side sequence collector  124 , only the bag side sequence collector  124  will be discussed in detail with a reference to one also referring to the other.  
         [0047]     In  FIG. 9  and within the bag side sequence collector  124 , the ply surface collectors  136  (and  134  as shown in  FIG. 8 ) are shown. The ply surfaces were created as split surfaces, placed in the appropriate collector and then associated with material and orientation specifications. Note that the ply orientation was modeled by associating a property  150  with the collector  136  which represents the ply. Also, it should be noted that each of the ply surface collectors  136  has a unique name. All plies within a sequence, though, may be assigned the same color (to enhance visualization) and layer properties.  
         [0048]     Each of the ply surface collectors  136  also has associated with it and filed in the bag side sequence collector  124  collector design history recording the operations used to create it. These operations may be played back or otherwise accessed to aid development team members in understanding and using the design. Since the subsequent functioning of a model critically depends on how the part was modeled, access to such information is critical to an understanding of the design. Accordingly, the sequences and plys represent critically important design history and intent heretofore unavailable to much of the team.  
         [0049]     At this juncture, several aspects of the present invention should be noted. First, the surfaces  134  and  136  representing the plies use only native CAD geometric shapes, namely surfaces. Second, the material associations  142  and  146  may be made using data accessible to non-composite specific licensed viewers (e.g. low-end viewers). Also, design intent such as  148  and  150  is likewise accessible to non-composite specific licensed entities. Additionally, the stacking order of the composite plies may be determined from the order of the sequences containing the plies, as seen in the specification tree, or from the stacking offsets.  
         [0050]     Referring back to  FIG. 5  for a moment, note that tool  120  and bag  124  side sequence collectors are shown in the tree structure  88  as being separated by the core sequence collector  122 . Within the core sequence collector  124 , the sequence used to create the solid core model may be found. It is the solid core model from which the surface used to represent the first bag side ply is extracted.  
         [0051]     Having now modeled the composite part using only CAD native geometric shapes and associated properties, the full capabilities of the CAD application may be exploited to further develop the composite part. Moreover, low-end viewers may now view detailed design information regarding the composite part. For instance, in  FIG. 11 , a low-end viewer can access a cross sectional view  174  of the composite part, as well as the perspective view  176  of the composite part.  
         [0052]     Likewise, in  FIG. 12 , a low-end viewer may access other design details of the composite part, which were heretofore unavailable to the low-end viewer. For instance, a display box  178  shows various geometric characteristics of the composite part. The geometric properties include the area  180 , volume  182 , density  184  (used with the geometric properties to compute other quantities), and mass  186 . In addition, the principal moments  188  and inertia matrix  190  may be seen. Likewise, the orientation and material properties of each ply could be accessed by a low-end viewer.  
         [0053]     In sharp contrast, previous design processed resulted in a drawing based representation of an encoded 3-D model (or models) similar to that shown in  FIG. 13 . A key characteristic of this method is that the geometric representation  192  of plies is incomplete and must be supplemented by numerous tables (e.g.  194  and  196 ), notes  198 , layer maps  200 , supporting surfaces  202  and numerous 2-D section views  204  in order to attempt a comprehensive definition. Worse still, with previous processes, the wireframe boundaries for the model  192  were on the wrong surface and the textual notes  198  were stored in separate files from the model  192 .  
         [0054]     In accordance with the principles of the present invention, the Layer map  200  and Ply Table  196  are replaced by a specification tree  88  (see  FIG. 5 ) which organizes all of the composite related data into logical collectors. Textual Flag notes are addressed by CATIA Version 5 Note Object Attributes or parameters embedded in the specification tree  88 . Thus, the many advantages of the present invention flow from using trimmed surfaces (versus several wireframe boundaries) related to a parent surface via proprietary construction techniques and formats. The more explicit nature of the surfaces resulting from the present invention allows for easier visualization and utilization of the ply definitions without a dependency on upstream processes.  
         [0055]     Thus, the present invention provides a complete three-dimensional model of any composite part. Moreover, the part definition may be viewed by any development team member having either a CAD application license, or, more importantly, a low-end viewer. Furthermore, the team member may be at any development location and still access detailed design information regarding the composite part. In particular, manufacturing personnel may access the model of the composite and modify data to enhance manufacturability of the composite parts.  
         [0056]     Accordingly, composite parts developed in accordance with the present design enjoy lower development costs, a higher quality design, more thorough understanding of the part, and superior performance over those designed in accordance with the previous design methods. Also, since the present invention employs only CAD native shapes the associated model may be ported to different CAD application environments thereby improving the flexibility of the development team.  
         [0057]     While various preferred embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the inventive concept. The examples illustrate the invention and are not intended to limit it. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.