Enabling composites material selection for automotive
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With the increased usage of composite materials in the automotive industry the importance of simulation is equally gaining ground. Crash testing is very expensive and established test methods are not applicable for the assessment of composites. In the UK-DATACOMP project Granta Design collaborated with partners to develop a database which provides simulation experts with validated material data as well as facilitating information exchange within the supply chain.
Lightweighting is a driving factor in many industry sectors — and polymer-fibre reinforced composites, with their unrivalled combination of strength and light weight for many applications, are a key materials technology in achieving lightweighting goals. For the automotive sector, the need to comply with increasingly stringent CO2 and other emissions regulations has focused attention on the potential of composites and, specifically, on the use of simulation to better understand the processes involved and to optimise performance.
Established test methods are inadequate to capture the properties of the more complex composites architectures.
It isn’t just the automotive sector that is interested in the solutions offered by composites. Aerospace is also developing the next generation of composite materials that are required as the sector moves towards ever higher volumes. Both Formula One and the marine sector are also watching with interest.
Challenges for the Automotive Sector
One of the principal challenges for auto motive enterprises is to manufacture composite components in high volumes at affordable costs which still meet the high strength performance criteria required for passenger safety. The unidirectional (UD) composites used for aerospace are expensive material-wise, time-consuming to process, and often do not meet the form ability requirements of automotive parts. In response, new systems are being developed using non-crimp fabrics, 3- D- weave- architectures, and braids using infusion and wet-press processes to offer manufacturing flexibility, and hybrid systems (for example, combinations of carbon/glass/polymer reinforcement) to lower costs while retaining strength and toughness performance.
With new material systems come new challenges for testing and simulation. Full-scale testing for automotive crash- worthiness is expensive. In addition, established test methods are inadequate to capture the properties of the more complex compo sites architectures, which arise from factors such as variation in the geo metry and part processing. Simulation plays a vital role in understanding these complex architectures — helping to interpret test results, to provide complementary insight, and to focus testing efforts and thus reduce their cost. But this requires improved confidence in predictive Computer-Aided Engineering (CAE) results and more widespread use of these methods. This in turn demands better simulation-ready data to support crash simulation of composites, and increased validation of methods.
The UK-DATACOMP Project
The objective of the UK-DATACOMP collaborative project was to establish a materials database to validate the use of simulation methodologies in composite product development. The material database also facilitated the validation and quality assurance of composite materials that are used within the UK supply chain. The project partners were drawn from across industry and public organisations, including Altair, Axon Automotive, Granta Design, Imperial College London, the UK’s National Composites Certification and Evaluation Facility (NCCEF), Sigmatex, and Solvay (formerly Cytec). Other objectives of the pro ject (funded by the UK Department for Business, Energy and Industrial Strategy) included standardising and harmonising the quality, reliability, and accessibility of material data provided by the composite supply chain, facilitating material selection for product developers and reducing time-to-market for end users and creating a material card library for automotive crash analysis.
The Role of Materials Information Management
▸ capture and share high-quality, pedigree-assured composites test data which could then be used to support the derivation of simulation models as input for finite element analysis (FEA)
▸ manage these complex simulation models — for example, catalogue them, share them, support the choice of the right model for the right application
▸ prepare the models for use with different solvers, such as Radioss, LS-Dyna, PamCrash, and Abaqus
▸ access the models quickly and easily from within simulation software (for example GRANTA MI:Materials Gateway for HyperMesh).
The database allowed partners to store pedigree information which linked the needs of test houses and simulation experts.
From Test Data to Simulation Model Validation
A wide range of materials were manufactured and tested in the project. Sigmatex developed and provided non-crimped fabrics, 2-D- and 3-D-fabrics (layer-to-layer, angle interlock), spread tow woven fabrics, and fabrics with hybrid reinforcement. Axon Automotive provided a braided material, and Solvay provided matrix material for the project and manufacturing capability. NCCEF, a UCAS certified test house, provided services for manufacturing and standard composite testing, and Imperial College London developed novel test methods to validate the material cards for damage behaviour at the coupon and sub-component levels, and provided manufacturing capabilities.
The project provided an example of how the multi-component nature of composite systems, and the strong dependence of their properties on factors such as geometry and processing, makes managing composite information a particular challenge. Characterising these systems generated large quantities of inter-related data, and a significant amount of testing was needed for each material, both at the coupon and component level. For 19 materials, there were 1000 tests — 969 at coupon level (7 typical standard test methods, and 5 test methods adapted from aerospace), 24 at sub-system level and 7 scaled parts at system level. As noted, tests established for unidirectional prepreg for the aerospace industry require adaptation to accommodate the new material architectures. Specifically, an adapted notched curved compact tension (NCCT) specimen was developed by Imperial College to address specimen buckling issues. Stitch-type for non-crimp fabrics was investigated, and resin and fibre properties were also tested for multi-scale modelling approaches.
Applying the Data in Simulation
Altair and Axon provided simulation expertise for the project, both applying a coupon correlation technique for major explicit solvers (Radioss, LS-Dyna, Abaqus and Pamcrash). A building-block approach was used to understanding material behaviour from coupon-to-system level, simulating tests using FE modelling and an iterative approach to correlating the material cards. Altair developed a tool that streamlined the validation process by taking processed data from the database and running single element models on the coupon geometries, updating the material card entries for damage behaviour before use in the four solvers (as noted above). The tool allowed the user to achieve a best fit of the materials properties from the various tests, enabling a good level of correlation to be achieved. The validated material models were accessible from the database via GRANTA MI:Materials Gateway, which allows users to apply material cards quickly and traceably, within Computer-Aided Design (CAD), CAE, or Product Lifecycle Management (PLM) software. GRANTA MI:Materials Gateway for HyperMesh was developed within the UK-DATACOMP project.
Outcomes from UK-DATACOMP Project
▸ a supply chain capability for com posites characterisation, design, and simulation, brought together in a unified workflow and centralised materials data management for the transfer of information between supply chain actors
▸ novel test methods for model validation
▸ tools to support the capture of experi mental data and information for the generation of material cards and their traceable integration with design and simulation tools
▸ a streamlined method for material model parameter correlation and validation
▸ a new data set for 19 polymer-carbon composites systems, including fibre and matrix properties, accompanied by 26 validated material cards for select systems across 4 solvers for 7 materials.
The final materials database built by the project is a rich resource of fully-traceable material, process, test and simulation pedigree, containing raw data, analysed data and design allowables. The project demonstrated how the new GRANTA MI:Materials Gateway enabled HyperMesh users to directly access validated material models. Data could be exported for other simulation software.
The materials database is a rich resource of fully-traceable material, process, test and simulation pedigree.
In building this database, the project started with a configurable, industry-standard data structure (a so-called “schema”) and related software tools to capture and process the specifics of composite data types and their inter-relationships. The schema, developed by Granta, embodies industry best practice for managing composite data, to efficiently qualify new materials, ensure traceability, and future-proof knowledge. The UK-DATACOMP project demonstrated its effectiveness and validated its use to support composite simulation. The GRANTA MI software is developed in collaboration with leading enterprises worldwide that use it to manage their corporate materials knowledge, including members of the Material Data Management Consortium (MDMC), such as Airbus Helicopters, Boeing, Honeywell, NASA, and Rolls-Royce. It is available for purchase by other organisations with composite data management requirements.
In summary, the UK-DATACOMP provided valuable reference data and validation of approaches to simulation that will enable the selection of composite materials which have the potential to be exploited for automotive, as well as aerospace, Formula One, and marine applications.