https://ntrs.nasa.gov/search.jsp?R=20150010341 2017-09-14T05:42:59+00:00Z National Aeronautics and Space Administration Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors Kirsten P. Duffy – University of Toledo / NASA GRC Bradley A. Lerch – NASA GRC Nathan G. Wilmoth – ASRC / NASA GRC Nicholas Kray, Gregory Gemeinhardt – GE Aviation www.nasa.gov SPIE 2012 Smart Structures/NDE March 14, 2012 1
National Aeronautics and Space Administration Background • Idea: – Use piezoelectric sensors and actuators as part of active vibration control of composite fan blades – Embed the piezoelectric elements into the composite material • Question: – How does the inclusion of packaged piezoelectric elements into composites affect the strength? • Previous Research: – Generally full inclusion of piezo into composite: • Warkentin and Crawley (1991) – embedded silicon chips • Bronowicki et al. (1996) – tension, compression, temperature, fatigue • Mall et al. (1998, 2000) – tension, electromechanical fatigue • Paget and Levin (1999) – tension and compression • Lin and Chang (2002) – fabrication techniques; tension, compression, shear, quasi-static impact • Konka et al. (2012) – foam sandwich structures, flexible piezoelectric elements; tension, bending, short beam shear • Our goal – Determine localized strength of the composite with embedded piezoelectric elements www.nasa.gov 2
National Aeronautics and Space Administration Approach Embed off-the-shelf piezoelectric sensors into carbon fiber composite material Mechanical Testing – 4-Point Bending – Short Beam Shear – Flatwise Tension Vibration Sensor Testing – Effect of curing temperature and pressure on sensor • Application to composite fan blades – Active vibration control: Spin testing with surface-mounted piezoelectric elements in small subscale fan blades • Vibration testing with embedded piezoelectric elements in larger subscale fan blades www.nasa.gov 3
National Aeronautics and Space Administration Materials Composite Type Description Material Epoxy resin with Polymer matrix HexPly 8551-7 unidirectional carbon fibers, fiber composite with IM 7 carbon fibers ply stack-up Piezoelectric Type Description Elements Non-flexible, PZT-5A, 250 m m (0.010”) thick PZT Monolithic solid material 175 m m (0.007”) thick PZT Flexible, PZT-5A, Flexible-1 rectangular fibers fibers 250 m m (0.010”) thick PZT Flexible, PZT-5A, Flexible-2 circular fibers fibers www.nasa.gov 4
National Aeronautics and Space Administration Mechanical Test Specimen Preparation Cured at 175 o C (350 o F) Piezoelectric Ply Cut-outs and 690 kPa (100psi) Element for two hours Bending and Flatwise Short Beam Shear Tension Composite Embedded piezoelectric patch Specimen cut www.nasa.gov 5
National Aeronautics and Space Administration Mechanical Testing f 6.4 mm loading nose 75.6 mm (16t) piezoelectric material t Force 151 mm (32t) piezoelectric material 4-Point Bending f 6.4 mm loading nose piezoelectric material t Flatwise Tension 50.8 mm (4t) Short Beam Shear www.nasa.gov 6
National Aeronautics and Space Administration Mechanical Testing Test Type Standard Specimen Dimensions Piezoelectric Location Two patches, 4-Point ASTM 165 mm x 12.7 mm x 4.72 mm piezo surface 0.3 mm (0.012”) (6.5” x 0.5” x 0.186”) Bending D7264 below PMFC surface Short Beam ASTM 76 mm x 25 mm x 12.7mm One patch (3.0” x 1.0” x 0.5”) Shear D2344 located at midplane Flatwise ASTM 22 mm diameter x 20 mm thick One patch (0.88” dia. x 0.78” thick) Tension D7291 located at midplane www.nasa.gov 7
National Aeronautics and Space Administration 4-Point Bending Baseline Embedded Failure Failure under Failure at roller interface www.nasa.gov 8
National Aeronautics and Space Administration 4-Point Bending y x z Observation area Embedded Baseline Shear Strain Shear Strain piezo www.nasa.gov 9
National Aeronautics and Space Administration 4-Point Bending 1200 1000 Strength (MPa) 800 Failure at roller 600 400 200 0 Baseline Monolithic Flexible-1 Flexible-2 (n=3) (n=2) (n=3) (n=5) www.nasa.gov 10
National Aeronautics and Space Administration Short Beam Shear failure PZT failure y Embedded Baseline x z Observation area piezo e y e y www.nasa.gov 11
National Aeronautics and Space Administration Short Beam Shear 90 80 70 Shear Strength (MPa) 60 50 40 30 20 10 0 Baseline Monolithic Flexible-1 Flexible-2 (n=3) (n=3) (n=5) (n=5) www.nasa.gov 12
National Aeronautics and Space Administration Flatwise Tension piezoelectric piezoelectric fibers fibers void Failure within patch Failure within patch at interface at piezoelectric www.nasa.gov 13
National Aeronautics and Space Administration Flatwise Tension 45 40 35 30 Stress (MPa) Failure in epoxy 25 20 15 10 5 0 Baseline (n=3) Flexible-1 (n=4) Flexible-2 (n=4) www.nasa.gov 14
National Aeronautics and Space Administration Vibration Testing ASTM E756-05 Beam Dimensions Patch Patch Patch Configuration Embedding (Beyond Clamp) Dimensions Properties Sensitivity ID Depth 0.3 mm (0.012”) Flexible-1-1 deep 191 mm (7.5”) long C = 25 nF 10x10 -6 28.0 mm x 14.0 mm 33.0 mm (1.3”) wide E = 30.3 GPa (1.10” x 0.55”) m/m/V 5.66 mm (0.223”) thick d 31 = -210 pC/N 1.5 mm (0.060”) Flexible-1-2 deep www.nasa.gov 15
National Aeronautics and Space Administration Vibration Testing 12 120 Sensor Strain (microstrain) Sensor Peak Output (V) Flexible-1-2 Flexible-1-2 10 100 Flexible-1-1 8 80 6 60 4 Flexible-1-1 40 2 20 0 0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0 40 80 120 Tip Displacement (mm) Calculated Strain (microstrain) www.nasa.gov 16
National Aeronautics and Space Administration Conclusions • Mechanical Testing – 4-Point Bending – 31-47% reduction in strength – Short Beam Shear – 19-29% reduction in strength – Flatwise Tension – 83-85% reduction in strength • Vibration Testing – Curing process did not adversely affect sensing ability • Improving Strength – Active vibration control will reduce resonant stresses in the structure; however, it may not be adequate to account for the reduced composite strength – Perform analysis to better understand stresses in and between composite and piezoelectric elements – Investigate embedding techniques to reduce stresses in piezoelectric elements (e.g. interlacing) – Develop packaging techniques to increase the strength in piezoelectric elements • Plans – Embed piezoelectric elements into subscale composite fan blade, perform active vibration control of resonant modes www.nasa.gov 17
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