End-to-end solution for mass-producing composite vehicles

  • 06-Nov-2012 04:58 EST

Example of a structural component designed and manufactured with composites materials.

Successfully utilizing composites structures in production vehicles requires substantial improvements in the tools used for end-to-end product development. Most existing CAD solutions are intended for use with metal and plastic parts of less complexity and offer no way to track laminate and composites properties, other than manually via spreadsheets.

From a simulation perspective, evaluating the mechanical performance of the proposed design is challenging because ply and composites parameters must normally be manually re-entered in the FEA software—a time-consuming and error-prone process. Additionally, most of today’s FEA software is designed for metallic materials that yield, bend, and fold when they fail whereas composites crack, fracture, and delaminate.

In manufacturing, the complex shape of automotive body geometries makes it difficult to predict how composite materials will conform to the mold’s complex surface. A major hurdle lies in developing flat patterns that will meet the ply guidelines without fabric distortion. The prevalent procedure is to cut fabric plies by hand and try to fit them on the mold tool. This process is time-consuming and can lead to costly errors in the positioning of the plies on the mold.

Currently, composites process planning does not take advantage of the product definition embedded in the 3-D model. Typically, composites process plans are created using manual entry or finite-element mesh defining plies that do not match the as-built models. While traditional software solutions cover the design, analysis, and manufacturing of composites parts, they do not do so using a collaborative process. This inability to quickly analyze the impact of design changes on manufacturing further extends the time needed to deliver product.

To meet these challenges, Dassault Systèmes (DS) has worked in close collaboration with industry leaders to develop end-to-end PLM solutions to design, simulate, and manufacture composites structures on a single virtual platform. At the heart of this solution, CATIA provides a dedicated environment for design of composite parts, SIMULIA provides advanced simulation tools and composites-specific methodologies to improve the design, and DELMIA supplies digital manufacturing capabilities from planning to actual delivery to the shop floor.

A complex design process

Composites numerical definition is complex and involves many different parameters as compared to metals, which are isotropic. As a result, it’s a challenge when modeling composites to find the right balance between the number of parameters necessary and the computation time needed. The CATIA Composites (CPD) solution provides accurate characterization based on material property data that allows engineers to quickly define a detailed composite lay-up.

Another challenge is the necessity to quickly explore and test many different variants in the preliminary design phase. Critical at this stage is the ability to create and update the composites models within hours of a design change. CPD offers various methods for the automatic creation of plies and provides associativity between surface and composites parameters. When surfaces change, the model is automatically updated based on the new surfaces, enabling significant time savings. This approach also offers improved accuracy, reducing the number of physical prototypes needed.

Designers need to also perform analysis on the composites parts early in the process, in order to understand the behavior of the various materials and their mutual interaction. CPD delivers a comprehensive set of inspection tools to review the composites structure in detail.

To achieve design weight and strength optimization, as well as ensure the final product performs as designed, it is necessary to integrate the design, analysis, and manufacturing process on a single platform. Metal components are joined either by welding, rivets, bolts, or bonding. For composites the assembly process can be quite different. Designers need to understand the composites material properties and the manufacturing assembly process, as well as the potential impact on the parts they are modeling. With CATIA Composites, productive features are provided so the designer can take them into account early in the design phase, helping to reduce the design lifecycle and allow manufacturers to go to market faster.

Additionally, designers need to simulate the manufacturing process in order to visualize the fiber orientation of the material on the shop floor, to ensure that the final product adheres to the original design intent. DS works with technology partners to provide advanced specialized applications that fully integrate with the CATIA environment to improve part quality and prevent delays in production. Engineers can visualize the ply stacking and tweak the laminate structure before the design is sent to manufacturing.

Properties and crash simulation

Composite materials behavior is complex and more difficult to predict than metals, so reliable simulation applications are key in understanding part behavior. Additionally, raw materials manufacturers constantly introduce new materials, and parameters need to be established. Relying on fully integrated partner products, this solution allows users to quickly define the complete properties of a new material and drape it on the mold.

The loss of information and time required to transfer composites data between CAD and CAE applications often requires data translation. The integration of CATIA information with SIMULIA CAE FEA software overcomes this issue. The ability to directly transfer accurate fiber angles and ply thicknesses from the design to the analysis environment improves simulation accuracy. Transferring updated design information from analysis seamlessly back to design enables designers and analysts to work collaboratively to ensure the analyzed model matches the final structure and to prevent specifying plies and structures that cannot be manufactured.

Composites assemblies’ failure analysis requires a comprehensive analysis of crash worthiness and other severe events inherent to composites, which are all addressed by this solution.

From manual to automated manufacturing processes

Shifting from high-volume metal parts to composite structures is a challenge for OEMs and Tier suppliers. The high cost of raw material as well as the lack of automated and repeatable manufacturing processes are preventing composites from being widely used in mass production. DS DELMIA Composites Planning takes advantage of ply stacking and composites properties from the CATIA model to deliver process planning capabilities needed to automate manufacturing processes.

With low volumes, a manual process is recommended; for medium to high volumes, an automated process is more suitable. With manual lay-up, automotive manufacturers are reaching a quality limit because it’s difficult to predict the exact final finish of a part on the shop floor. The operator may not deposit the ply consistently at the same position, jeopardizing the precise initial design. To help the operator accurately lay the fabrics on the mold, best-in-class industry solutions are fully integrated in the design environment for nesting, cutting, and laser projection systems optimizing the ply lay-up of a composites model with the highest degree of accuracy.

With automakers able to implement an end-to-end solution for composites, the industry is increasing its use of fiber-reinforced composites for a wide range of applications, which allows them to reduce their time to market and avoid costly errors while minimizing vehicle weight and cost and preventing overdesign.

Rani Richardson, Product Specialist at Dassault Systèmes, wrote this article for SAE Magazines.

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