The Composites Design and Manufacturing HUB will convene the composites community to advance certification by analysis by increasing the number and use of simulation tools by an order of magnitude through education and evaluation of existing and emerging simulation tools.
The goals of the cdmHUB are to:
- Advance the certification of composite products by analysis validated by experiments.
- Educate the current and future generations of engineers in the use of composite simulation tools.
- Evaluate composites simulation tools to determine functionality, compatibility and maturity.
- Develop a comprehensive set of simulation tools that connect composites from their birth in manufacturing to their lifetime prediction and accelerate the rate of development by an order of magnitude.
- Work with industry, academia and government to put these tools in the hands of engineers who will design future products that require the performance characteristics composite materials offer.
What is cdmHUB?
The Composites Design and Manufacturing HUB (cdmHUB) is a collaborative web interface platform designed to enhance and build synergies among the composite community by enabling users to interact 24 hours a day, seven days a week. The platform was developed to host the simulation tools needed to: advance composite materials design, certify product integrity, simulation manufacturing solutions, and accelerate the talent-base of composite materials developers and users. The cdmHUB will showcase emerging simulation tools, evaluate existing and emerging simulation tools and host simulation challenges to educate and unify the composites community.
This web site is a resource for research, education and collaboration in the composites field. It hosts various resources which will help you learn about composites design and manufacturing, including Online Presentations, Courses, Learning Modules, Animations, Teaching Materials, and more. These resources come from contributors in our community, and are used by visitors from all over the world.
Most importantly, cdmHUB.org offers simulation tools which you can access from your web browser, so you can not only learn about but also simulate the composites design and manufacturing process. An article by Dr. R. Byron Pipes in the June 1014 issue of Composites Manufacturing Magazine further introduces the cdmHUB.
Education in Composite Simulation Tools
The resources, including simulation tools and other materials on the cdmHUB will educate the current and future generations of engineers in the use of composite simulation tools, beginning in the classroom and continuing into engineering practice. The content on the cdmHUB will aim to address the following key questions:
- What tools are available for composites simulation?
- What tool is best for a specific problem?
- What are the functionalities of a specific tool?
- How is a particular tool used along with other tools?
As a vehicle to convey this information, the cdmHUB will develop and host the on-line Journal of Composites Simulation, an online journal of engineering and scientific papers describing composites simulation with archival journal review standards and knowledge codification. "Active" equations where the reader can exercise the models described in the papers with "active" links to simulation codes and an "active" database of experimental and simulation data will take advantage of the unique HUB-based platform, while increasing author impact and promoting education and evaluation of simulation tools.
Development of the simulation tool taxonomy will enable education and evaluation of composites simulation tools. The simulation tool taxonomy may be addressed by the following questions:
- Scientific law: a) Solids: mechanics of materials, 2D-elasticity, 3D-elasticity, plate theory, shell theory; fracture mechanics b) Fluids: non-Newtonian, rate and temperature dependence, suspension rheology, infusion and diffusion flows; c) heat transfer: conduction, convection, anisotropy; d) kinematics and motion: rigid body dynamics, vibrations.
- Scale and Homogenization: what are the systems homogenized and at what scale to yield properties or behavior of the homogenized system. Fiber and matrix are the answer for micromechanics and the homogenized products are the effective anisotropic properties. Multi-axial laminae are the answer for the laminate. Laminates are the answer for the simple composite structure, and so on.
- Mechanism: a) Solids: elastic small deformation, large deformation, geometric non-linearity, material non-linearity, crack propagation, damage development and propagation, energy absorption and dissipation, creep, relaxation, orientation evolution; b) Fluids: impregnation, consolidation, infusion, molding flows, orientation evolution; c) Heat Transfer: conduction heating, convection heating, induction heating, microwave heating; d) Kinematics: tape laying, advanced fiber placement, drape forming, pultrusion, filament winding.
- Solution form approximation: closed-form solutions, algebraic equations, differential equations, integral equations, finite-difference method, finite-element method: element characteristics and continuity level, cohesive elements, advanced mathematical methods.
- Computational efficiency: PC compatible, cluster required, cloud computing required.
- Links and compatibility to input and output tool codes: codes that provide input to this code and codes receive this code output as input.
- Tool Maturity Level (TML) description is given in Table 1 after Cowles et al. Integrating Materials and Manufacturing Innovation 2012, 1:2
- Ease of use and ease of interpretation.
We welcome your feedback in developing the simulation tool taxonomy. See an example of a taxonomy for the Free-Edge Elasticity Solution tool. click the following link.
Another educational vehicle are the tools themselves. The tools on the cdmHUB can be used to educate and explore the breadth of composites simulation, including micromechanics, laminated plate theory and free-edge stresses.
A final vehicle for education will be composite simulation challenges. Similar to the World-Wide Failure Exercise, composite simulation challenges will evaluate the functionalities of current simulation tools in areas of interest to the composites community. Composite simulation challenges in composites design and manufacturing will be developed by the cdmHUB community and will showcase academic, research and commercial simulation tools.
Accelerating Certification by Analysis
The design and certification of composite products remains driven by exhaustive experimental testing without the full benefit of simulation. This approach significantly increases the cost of product development, retards the development of new materials systems and limits product diversity. Major aircraft OEM’s spend millions of dollars and allocate thousands of man hours annually to test and re-test designs for certification. That testing is further extended when a design change comes into play. For maintenance and repair (MRO), the certification process may be even more complex since the nature of repair is unpredictable and the in-field re-manufacturing is quite different from that in the factory.
Once the design is complete, the exhaustive physical testing begins. Whether the structure is made up totally of composites or partially, the current certification process is time consuming, manual, and expensive to the OEM’s. The current process is designed to reduce risk, but it is not optimized to minimize costs and time to completion. Today, the software tools used for design and manufacturability are often disconnected and not based on the same platform necessary for inter-code communication. Furthermore, when the OEM’s handoff the design to their supply chains to test and/or build the components, it is likely the suppliers may not have access to the same simulation toolset as the OEM, thereby, increasing the cost and complexity of the evaluation and manufacturing processes. In many cases the component design handed off to the supply chain has focused solely on product performance and the part has not been designed for manufacturability. Since the design is typically frozen at this stage, the materials and manufacturing approach have already been selected. In addition, there are many other constraints placed on the supplier that must be adhered to during the fabrication process. All these restrictions can significantly limit innovation within the supply chain.
Sharing specialized design and manufacturing software with the supply chain in order to certify complex composite structures should significantly shorten the development lifecycle and decrease the development cost for OEM’s, while allowing more time for innovation by all. The composites simulation tool suite can be used as the platform for the certification of composite structure as well. Here again composites simulation tools can provide an economic alternative to exhaustive studies of process and performance variability. But to do so, simulation tools for prediction of manufacturing and performance variability must be developed and integrated into the certification process. Read more about accelerating the certification process for aerospace composites in the March 2014 issue of High-Performance Composites.
Evaluation of Simulation Tools
One approach to reduce cost and time of product certification is to first certify the simulation tools themselves. Certified simulation tools would be used by engineers with the expectation that, within the bounds of the certification, no further verification or validation would be necessary. This would result in enormous savings since the contemporary approach involves verification and validation testing by each user before the simulations can be trusted. Certification of composites simulation tools may not be a simple undertaking, however. First the taxonomy of the code must be clearly developed. The scientific principle, scale and level of homogenization, specific mechanism, solution form approximation, computational efficiency, communication compatibility and maturity level must be determined in the taxonomy of each tool. Next a rigorous process for verification and validation within clearly specified conditions must be developed and articulated.
Before simulation tools can be certified, their maturity level must be assessed. An innovative construct for this purpose, Tool Maturity Level (TML), has been recently proposed by Cowles, Backman and Dutton. TML is defined at five levels: TML1) The first level simulation tools are based on analytical processes that are exploratory in nature. Fidelity of predictions at this level is largely unproven, but predictions can provide some physical insight, while they cannot reduce development testing. TML2) At the second level, the simulation tool is a proven capability for comparative assessment, ranking or trending. Experimental validation is still necessary and tools at this level can drive development or the assessment plan and test matrix. TML3) For tools at the third level of maturity, the material or process can be developed or assessed with significantly reduced testing. There is the expectation that development iterations can be reduced or eliminated at this level. However, accuracy and uncertainty must be quantified experimentally and the range of applicability well defined. TML4) At the forth level, the material or process performance and impact on system or application are well understood. Accuracy and uncertainty effects must still be verified. Additional data may be required when applied to new materials or processes, or to extend range of application. TML5) The fifth tool maturity level is for tools in which all material and process performance and system interaction effects are understood within defined range of application and the tool can be applied without further testing.
Since variability drives certification, two additional levels of tool maturity are proposed: TML6) Level six is for tools where all material and process performance variability and system interaction effects are understood within defined range of application. TML7) The highest level of maturity, consistent with simulation tool certification, is an analytical process that can be applied to predict variability distribution without testing. Thus, prediction of performance or manufacturing variability with the same level of confidence as experimental testing must be the long term objective of this undertaking.
|Tool Maturity Level||Simulation Tool Maturity Description|
Analytical process is exploratory in nature. Fidelity of predictions is largely unproved. Provides some physical insight but cannot reduce development testing.
Proven capability for comparative assessment, ranking or trending. Experimental validation is still necessary. Can drive development of assessment plan and test matrix.
Material or process can be developed or assessed with significantly reduced testing. Expectation that development iterations will be reduced or eliminated. Accuracy and uncertainty effects must be quantified. Range of applicability well defined.
Material or process performance and impact on system or application are understood. Accuracy and uncertainty effects must be verified. Additional data may be required when applied to new materials or processes, or to extend range of application.
All material and process performance and system interaction effects are understood within defined range of application. Analytical process can be used to predict mean performance without testing.
|7||Analytical process can be applied to predict performance and manufacturing variability distribution without testing.|
Simulation of the manufacturing of composite structure is not at the same level of development as that of design simulation. VISTAGY Inc. (Waltham, Mass.) recently announced the results of its composites engineering benchmarking survey entitled, "How does your Composite Design Processes Compare to Industry Best Practices?” The results of the study revealed that only 56 percent of the composite design companies surveyed considered themselves knowledgeable in composites manufacturing practices and were able to apply that knowledge during design. This suggests that 44 percent of companies need to enhance their knowledge of the manufacturing process if they are to improve their competitiveness.
The process for developing new manufacturing simulation tools remains in its infancy. Unlike design simulation software, the manufacturing of polymer composite materials and structures involves multi-physics phenomena such as the curing reactions of thermoset polymers, melting and solidification of thermoplastic polymers, flow and impregnation of viscous polymers in fibrous preforms and tows, consolidation of fiber preforms, conduction and convective heat transfer, geometric conformation of fiber preforms to curvilinear surfaces, residual deformations due to anisotropy in thermal expansion and tooling-composite thermal interactions. These phenomena span the disciplines of polymer science, rheology, reaction kinetics, fluid mechanics of non-Newtonian liquids, heat and mass transfer, mathematical topology, anisotropic thermoelasticity and viscoelasticity. While multi-physics analysis tools have recently been introduced, their use in composites manufacturing simulation is still quite early. Commercial tools now offer a broad range of physical modeling capabilities to model flow, turbulence, heat transfer and curing reactions for industrial applications.
The manufacturing of high performance advanced composite materials is moving from a single dominant approach, in which an autoclave provides high levels of control of process conditions and pressures significantly greater than atmospheric, to multiple approaches wherein the experience base is less well developed and the corresponding product variability has not been well characterized. Decisions for choice of manufacturing approach are currently being made with only the initial manufactured cost as a guideline, while the variability in product performance should be considered as well. Thus, variability in material and structural performance due to manufacturing choices is an essential element in development of accelerated certification methods.
Rigorous simulation models that capture the phenomena related to manufacture and performance, such as processibility, strength and durability of composite materials and structures can provide the vehicle for taking known variability from its source to material or structure performance. One approach already demonstrated is the capture of microstructural feature variation of continuous carbon fiber prepreg materials. High performance carbon fibers are manufactured from polymeric fibers produced in a spinning process and spooled in yarn or tow form. The fiber and polymeric matrix are combined into the prepreg form typically through hot melt impregnation. When the fiber tows are impregnated with the polymer in its liquid state, it is desired that the fiber positions within the material cross-section be uniformly spaced and fully surrounded by the polymeric matrix phase. However, local control of fiber spacing is not possible and variability in fiber spacing and local fiber volume fraction result. Since composite effective properties, as well as, the local stress state in the composite are strong functions of fiber volume fraction, variability in fiber spacing and volume fraction is one known source of variability of the material performance that can be simulated. In addition, undetectable defects can also produce variability in material performance.
Benefits to the cdmHUB community of sustaining sponsors, commercial simulation tool providers, composites simulation tool users and developers include:
- Convene the composites community.
- Education in the use of composites simulation tools:
- What tools are available?
- What tool is best for a specific problem?
- What are the tool functionalities?
- How is a particular tool used along with other tools?
- Browser-based access to educational material and simulation tools.
- Expert evaluation of simulation tool taxonomy and Tool Maturity Level (TML).
- Establishment of protocols for simulation tool validation and verification (V&V).
- Access to data sets required for TML and V&V.
- Ongoing record of simulation tool use.
- Needs analysis for simulation tool development.
- Tool development for manufacturing and processing simulation.
- Composites Simulation Challenges.
In the April 2014 issue of High Performance Composites, Rani Richardson of Dassault Systemes discusses the need for and benefits of the cdmHUB to the industries serviced by composite materials. In the February 2015 issue of Composites World, Dale Brosius discusses modeling and simulation in the context of ICME and composites manufacturing.
Convening the Composites Community
Take a tour of our web site and see how you can use our infrastructure to improve your knowledge of composites and contribute to the community. Create your own account. It's free and will give you access to our online simulation tools and other features. Become a contributor by uploading your own simulation tools and other resources for others to share. Ask a question in our community forum, and let the community help you out.