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Improved Methods for Measurement of Extension-Twist Coupling in Composite Laminates

Improved Methods for Measurement of Extension-Twist Coupling in Composite Laminates. Michael D. Schliesman. F. +a. s. s. -a. F. In-Plane Extension-Shear Coupling. Extension-Twist Coupling. Introduction. Coupling in Off-Axis Laminates. Introduction.

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Improved Methods for Measurement of Extension-Twist Coupling in Composite Laminates

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  1. Improved Methods for Measurement of Extension-Twist Coupling in Composite Laminates Michael D. Schliesman

  2. F +a s s -a F In-Plane Extension-Shear Coupling Extension-Twist Coupling Introduction • Coupling in Off-Axis Laminates

  3. Introduction • Want to Use Extension-Twist Coupling in Design • Experimental Validation of Analytical Method • Requires Precise Experimental Data

  4. Existing Testing Methods • Thrust-Bearing Apparatus • Rotating-Frame Apparatus • Air-Bearing Apparatus

  5. Improving the Rotating-Frame Apparatus • Benefits • High Fidelity to Rotor Blade Environment • Investigation of Aeroelastic Characteristics • Problems to Overcome • Restoring Moment • Poor Method of Data Acquisition

  6. Not Deflected Deflected POR POR Restoring Moment • Cylindrical End Mass

  7. Data Acquisition • Laser Twist Measurement q End Mass Window h Base q Laser Paper d

  8. Improved Rotating-Frame Apparatus

  9. +q [+a/-a] [-a/+a] F Symmetric Test Specimen -q F Twist of Specimen Components Symmetric Testing Method +q 0° F Net Twist of Specimen

  10. Symmetric Testing Method • Testing Setup

  11. Predictions • Analytical Method • Finite Displacement Analysis • Closed Form Solution • Geometric Nonlinear Effects • Numerical Method • Finite Element Analysis (ABAQUS) • 2200 S4R Elements • Geometric Nonlinear Effects

  12. End Twist (deg) Axial Load (N) Predictions • Analytical and Finite Element Predictions

  13. End Twist (deg) Axial Load (N) Testing Results • Rectangular vs. Cylindrical End Mass

  14. End Twist (deg) End Twist (deg) Angular Speed (rps) Angular Speed (rps) Testing Results • Aeroelastic Effect Chamber Not Evacuated Chamber Evacuated

  15. End Twist (deg) Axial Load (N) Testing Results • Scatter in Symmetric Testing Method

  16. Conclusions • Isolation of Extension-Twist Relationship • Cylindrical End Mass Eliminated Restoring Moment • Symmetric Method Provided Inconclusive Results • Dependent on Accuracy of Specimen Manufacturing • Simple Method Shows Promise • Vibration Visualization • 1P Sampling of Twist Provides Dynamic Measurement • Investigation of Aeroelastic Characteristics

  17. Future Work • Refine Symmetric Testing Method • Accurate Specimen Manufacturing • Accurate Twist Measurement • Submit Method to ASTM

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