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No abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY)January 2005 ARL-TR-3388 SPONSOR/MONITOR'S ACRONYM(S) 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES ABSTRACTComposite flywheels for energy storage have been proposed and investigated for the past several decades. Successful applications are, however, limited due to the inability to predict the performance, especially the long-term durability. In this investigation, a comprehensive study was proposed with the intent to implement composites in high-performance flywheels. The potential failure mechanism of flywheels constructed with fiber composites was evaluated. Analytical codes for predicting elastic and viscoelastic (long-term) behavior were developed for flywheel design. Material characterization and test matrices were proposed to design flywheels with maximum performance. Component-level test methods and devices were developed to validate flywheel performance. Finally, a methodology incorporating these studies is presented for the design and manufacture of composite flywheels. iii

Approved for public release; distribution is unlimited.ii REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY)December 2012 ARL-TR-6272 SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES* Bowhead Science & Technology, 4900 Seminary Rd., Ste. 1200, Alexandria, VA 22311 ABSTRACTThe purpose of this investigation is to assess the potential interchangeability of key material response metrics as measured using quasi-static indentation (QSI) and low-velocity impact (LVI). This report compares the response of a S2/SC-15 glass /epoxy composite material subjected these two test methods. Specimens of 102 × 152 × 5.5 mm were quasi-statically indented at load rates in the range of 1.2 to 50 mm/min. Differences in material response over this range of loading rate were found to be negligible. The average value of peak input energy calculated from these QSI tests was used as the impact energy for subsequent LVI tests of identical specimens. Material tested using LVI (3.41 m/s velocity) exhibited higher initial stiffness and absorbed energy but with slightly lower maximum force and displacement values compared to material tested with QSI. Thirty QSI and LVI specimens were then evaluated with compression after impact (CAI) testing, and all specimens exhibited equivalent CAI strengths. Lightbox and cross-section analyses showed that material tested under LVI exhibited significantly less delamination and significantly more intralaminar fracture compared to QSI. For these reasons, LVI and QSI data are not interchangeable for this material system. SUBJECT TERMS

ABSTRACT--Conceptual improvements to a non-contact optical strain measurement technique for high-speed flywheels are presented. The improvements include a novel reflective pattern that allows for greater displacement sensitivity, the ability to measure rigid body vibrations and separate the associated vibration-induced displacement from the strain-induced displacement, and the ability to compensate for potential sensor drift during flywheel operation. The effects of rigid body rotor vibrations and sensor drift have been modeled and techniques to compensate for the errors associated with such effects are presented. Experimental results validate the ability of the technique to separate such vibrations from axisymmetric flexible body displacements, and to compensate for errors due to in-plane and out-of-plane pattern misalignment and sensor drift. Displacement measurements made on an aluminum rotor operating at a maximum speed of 16 krpm (255 m/s at the point of measurement) were made with 4-1 Ixm accuracy. At this speed, hoop strains were found to be within 40-125 I~ of theoretical predictions, provided a proper accounting is made for thermal strains. Relative to the theoretical hoop strains, the measured hoop strains differed by 5.0 to 6.4% at 16 krpm.KEY WORDS--Strain measurement, rotating, flywheel, noncontact, optical Nomenclature A0 = axisymmetric radial deformation of rotor due to strain A1 = amplitude of in-plane rigid body radial displacement of rotor a = inner radius of aluminum rotor b = outer radius of aluminum rotor d = shortest distance between edge of a reflective patch and center of illuminated spot E = tensile Young's modulus (isotropic) r = radial coordinate on rotor r / = a particular radial location on the rotor ri = inner radius of an annular region of an optical pattern rinst = radial location on rotor at instantaneous speed rma x = maximum radial location at which a hoop strain sensitivity can be achieved ro ----outer radius of an annular region of an optical pattern rre f = radial location on rotor at reference (negligible deformation) speed Sc = counter frequency (Hz) u = radial displacement Umi n = minimum detectable radial displacement Urack = radial displacement of sensor rack due to temperature change /,/theory = theoretical displacement of the aluminum rotor Utot = total radial displacement including thermal effects c~ = linear coefficient of thermal expansion for an isotropic rotor f3 = phase of in-plane rigid body radial displacement of rotor A T = temperature change of rotor ~r = radial strain (m/m) ~0 = hoop strain (m/m) = duty cycle (rad) (~inst = duty cycle at instantaneous speed ~ref = duty cycle at reference (negligible deformation) speed y = angular position on rotor v = isotropic Poisson's ratio 9 = material density 0min = rotor rotation during one counter increment (rad) 0a = apparent measured compensation patch angle (rad) 0c = correct compensation patch angle (tad) co = angular speed of rotor (rad/s) ~P = acute angle between trajectory of illuminated spot and displacement p...