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Practical Considerations In Determining Material Properties

Practical Considerations In Determining Material Properties . Susan I. Hill Structures and Materials Evaluation Laboratory University of Dayton Research Institute (937) 229-4704 hillsi@udri.udayton.edu www.udri.udayton.edu Future of Modeling in Composites Molding Processes Workshop

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Practical Considerations In Determining Material Properties

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  1. Practical Considerations In Determining Material Properties Susan I. Hill Structures and Materials Evaluation Laboratory University of Dayton Research Institute (937) 229-4704 hillsi@udri.udayton.edu www.udri.udayton.edu Future of Modeling in Composites Molding Processes Workshop June 9-10, 2004

  2. Defining Needs • Depends on application and model • Impact can be compressive event but material failure is tensile event • Localized delaminations, cracking, interfacial bonding in composites • Necessary test data are defined by selected model • Tensile, compression, and shear data • Energy absorption • Temperature effect • Strain rate effect • Failure

  3. Types of tests required May need to go beyond the typical tensile strength, modulus, failure strength data, e.g. • Uniaxial compression • Confined compression (bulk modulus) • Cyclic tension • Stress relaxation • Resonant Beam • ?

  4. Impact-related models • Material models exist for structural polymers • Lacking for composites • FE codes may not incorporate correct material models • Current models have poor handling of viscoelastic effects, plastic flow, strain rate effects, and fracture • Use of quasi-static data will underestimate material response at higher impact rates

  5. Polyolefin

  6. Polyolefin relationship with strain rate

  7. Polycarbonate

  8. Relationship with Strain Rate

  9. Highly glass-filled polymer

  10. Background information

  11. Defining Needs • Strain rate defines test method • Quasi-static -- Screw-type test machines • 0.0001 to 0.1/s • Intermediate (“High”) -- Servo-hydraulic test machines • 0.1 to 200-700/s • Bar Impact -- Split Hopkinson Bar • 200 to 10,000/s

  12. Types of high rate problems

  13. Comparison of tensile specimens used for quasi-static and dynamic tests ASTM D638 Type I ASTM D638 Type V Dimensions in mm.

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