Micromechanics Study of a Polymer with/without Microparticles

SIEM (Speckle Interferometry with Electron Microscopy) is a micro/nano experimental mechanics technique that is able to perform the full field displacement mapping over a region of only several microns in size. In this study we tested specimens made of a pure binder material, a polymer, and binder material mixed with 6 micron aluminum particles under uniaxial tension. The binder material with microparticles was made by adding 10% by weight aluminum particles into the pure binder material. The technique SIEM was used to map the strain distributions of the specimen under various magnifications, 40x, 200x, 800x, and 1500x. The relationships between the coefficient of variation of εyy, εxx and the examined area were obtained. We found at magnification about 200x the microstructure had a significant effect on the strain distributions in the binder material with microparticles whereas, for pure binder material, the effect was not observed until at 1500x. INTRODUCTION For the development of polymer systems with improved mechanical properties, it is important to understand the relationship between the morphology and micromechanical behavior of modified polymer systems. Many researchers have studied the structure-property relationships in polymers. In their studies, electron microscope was used as a tool for morphology study during the polymers deformation, and the mechanical properties of polymers were usually obtained by measuring their bulk material properties. The much more complicated strain distributions in micro scale have not been observed to the best of our knowledge. In this study, Speckle Interferometry with Electron Microscopy (SIEM) was used to map the full field deformation of polymers at various micro scales. The speckle interferometry (speckle photography) method is a full field technique of nondestructive evaluation (NDE). A random intensity distribution of any sort can be considered as a speckle pattern, and it may be naturally present or artificially created. The development of speckle technique evolves from the laser optical speckle technique , the white light speckle technique, and the digital speckle technique [8,9] . The digital speckle technique maintains all the advantages of conventional speckle photography but eliminates the tedious tasks of photograph development and fringe pattern analysis. Speckle Interferometry with Electron Microscopy is a micro/nano experimental mechanics technique that is able to perform the full field displacement mapping over a region of only several microns in size. There are three basic procedures in SIEM technique: the creation of micro/nano-speckle patterns, the recording and digitization of these patterns before and after specimen deformation and the analysis of speckle images. The displacement resolution of SIEM depends on the magnification and the number of pixels in each image. In the current system the image size is 4.5 inch × 3.5 inch. In the case where the magnification of the image is 1500× and the image consists of 2048×2048 pixels, the resulting physical size of a pixel is of 37 nm in X (horizontal) and 29 nm in Y (vertical) directions. Because SIEM usually can resolve at least 0.5 pixel displacement, the sensitivity of displacement at this magnification is about 19 nm in X and 15 nm in Y directions, respectively. Thus, by using an electron microscope, the sensitivity of speckle interferometry is increased by several orders of magnitude. EXPERIMENTS AND RESULTS Two polymer materials, pure binder material and binder material mixed with 6 μm aluminum particles, were tested. The binder material with microparticles was made by adding 10% by weight 6 μm aluminum particles into the pure binder material. Dogbone shaped specimens were tested under uniaxial tension inside the vacuum chamber of a Hitachi scanning electron microscope. The cross-section of the pure binder material specimen is 10.6 mm x 2 mm and that of the binder material with Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the 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 of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 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 a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 01 MAR 2004 2. REPORT TYPE 3. DATES COVERED 4. TITLE AND SUBTITLE Micromechanics Study of a Plymer with/without Microparticles 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Sheng Chang; C Liu; Fu-Pen Chiang 5d. PROJECT NUMBER 2302 5e. TASK NUMBER 0378 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Air Force Research Laboratory (AFMC),AFRL/PRS,5 Pollux Drive,Edwards AFB,CA,03524-7048 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT SIEM (Speckle Interferometry with Electron Microscopy) is a micro/nano experimental mechanics technique that is able to perform the full field displacement mapping over a region of only several microns in size. In this study we tested specimens made of a pure binder material, a polymer, and binder material mixed with 6 micron aluminum particles under uniaxial tension. The binder material with microparticles was made by adding 10% by weight aluminum particles into the pure binder material. The technique SIEM was used to map the strain distributions of the specimen under various magnifications, 40x, 200x, 800x, and 1500x. The relationships between the coefficient of variation of yy, xx and the examined area were obtained. We found at magnification about 200x the microstructure had a significant effect on the strain distributions in the binder material with microparticles whereas, for pure binder material, the effect was not observed until at 1500x. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 7 19a. NAME OF RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Approved for public release; distribution unlimited 2 microparticles is 10.6 mm x 1.4 mm. Figure 1 shows the v and u displacement fields of pure binder material at four different magnifications, 40x, 200x, 800x, and 1500x, under slightly different loadings. Figure 2 shows the corresponding εyy and εxx normal strain distributions.