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Through-the-Thickness Mechanical Properties of Smart Composite Laminates

Through-the-Thickness Mechanical Properties of Smart Composite Laminates. Gang Zhou , L.M. Sim, P.A. Brewster and A.R. Giles Department of Aeronautical and Automotive Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.

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Through-the-Thickness Mechanical Properties of Smart Composite Laminates

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  1. Through-the-Thickness Mechanical Properties of Smart Composite Laminates Gang Zhou, L.M. Sim, P.A. Brewster and A.R. Giles Department of Aeronautical and Automotive Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK International Conference on Composites Testing and Model Identification 28th January 2003

  2. Background and Motivation Smart composite structures: sensory and adaptive Sensory smart structures can monitor structural environment or detect and assess damage Adaptive smart structures can modify/control the host structural behaviour Embedded optical fibres/SMA wires affect short-term through-the-thickness mechanical properties? Facilitate the design of smart structures 2

  3. EFPI sensor Micrograph showing embedded OF

  4. Objectives • Whether or not defects associated with embedded OFs/SMA wires affect ttt mechanical propertiesif? • Under what conditions will these properties be affectedthresholds? • How are these properties be affected how much?

  5. Focal Points of Current Investigation: • Optical fibres: Orientation Number/volume fraction Through-the-depth location Stress concentration effect • SMA wires: Number/volume fraction

  6. Through-the-thickness mechanical properties and experimental techniques • Interlaminar shear (ILS) properties Short beam shear (SBS) method Iosipescu shear method • Flexure Three-point bending Four-point bending

  7. Specimen Manufacturing • Beam specimens • Acrylate-coated single mode OF of 0.25 mm dia. (OC) • Nitinol wire of 0.5 mm dia. (M-M) • T700/LTM45-EL carbon/epoxy prepreg (ACG) • Autoclave with a single-cycle cure at 600 C • EFPI sensors are cured at 650 C • Austenitic completion temperature of SMA wires is about 700 C • Iosipescu ILS specimens: two 900 notches

  8. Micrographs showing embedded OFs

  9. Micrograph showing embedded OFs

  10. Micrograph showing embedded nitinol wires

  11. Orientation and through-the-depth location

  12. Arrangement of OFs in the transverse direction

  13. Through-the-depth location of OFs in Iosipescu shear specimens

  14. ILS shear strength via SBS method OFs in the longitudinal direction OFs in the transverse direction Table 5 Table 4

  15. ILS shear properties via Iosipescu method with OFs in the transverse direction Table 6

  16. Flexure properties via 3-point bending method with OFs in the longitudinal direction Table 7

  17. Flexure properties via 3-point bending method with OFs in the transverse direction  -20% Table 8

  18. 3-point bending flexure properties with OFs in the longitudinaldirection Table 9

  19. 3-point bending flexure properties with OFs in the transversedirection  -25%  -32% Table 10

  20. 4-point bending flexure properties with 3OFs in the longitudinaldirection Table 11

  21. 4-point bending flexure properties with 5 OFs in the transversedirection  -14%  -26% Table 12

  22. Micrograph showing 5 embedded OFs

  23. SBS ILSS with SMA wires in the longitudinaldirection Table 13

  24. 3-point bending flexure properties with SMA wires in the longitudinaldirection Table 14

  25. Conclusions • Specimens containing OFs • Short-term ILS and flexural moduli: no effect • Short-term flexural strength with OFs at any TTT location in the longitudinal direction no effect • Short-term flexural strength degradation: • Transverse / Sym-Q / 3 OFs / 3-point Moderate (20%) • Transverse / Single-out Q / 5 OFs / 3-point Significant (25%) • Transverse / Sym-out Q / 5 OFs / 3-point Significant (32%) • Transverse / Single-out Q / 5 OFs / 4-point Moderate (14%) • Transverse / Sym-out Q / 5 OFs / 4-point Significant (26%) • Specimens containing up to 5 SMA wires • Short-term ILS strength and modulus: no effect • Short-term flexural strength and modulus: no effect

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