Continuous dynamic analysis: evolution of elastic properties with strain
- PDF / 385,526 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 77 Downloads / 266 Views
esearch Letters
Continuous dynamic analysis: evolution of elastic properties with strain S. Basu and J.L. Hay, Agilent Technologies, Chandler, Arizona 85226 J.E. Swindeman and W.C. Oliver, Nanomechanics Inc., Oak Ridge, Tennessee 37830 Address all correspondence to S. Basu at [email protected] (Received 30 September 2013; accepted 10 December 2013)
Abstract Mechanical strain triggers changes in inherent molecular structure, especially in polymeric and biological materials. Unlike conventional techniques, we demonstrate a novel dynamic mechanical characterization method to study the effect of this structural evolution with strain on elastic properties. During tensile characterization of small diameter fibers, we quantitatively measured the viscoelastic properties as a continuous function of strain. While this approach is useful to characterize the elastic properties of metal microwires independent of applied strain, it is extremely important for fundamental understanding of molecular changes and their effect on the viscoelastic properties in materials such as polymer fiber and spider silk.
The mechanical behavior at nano/microscale has been a subject of considerable interest in both the physical and biological sciences. The interest has been sparked by continued progress in the miniaturization of components for microelectronic applications,[1,2] synthesis of nanostructured materials for biomedical scaffolds,[3,4] as well as the recognition that many biological tissues and fibers exhibit superlative mechanical performance.[5–7] A good example is the sustained effort in characterizing, synthesizing, and understanding the behavior of spider silks, many of which are stronger than steel and exhibits higher toughness than Kevlar.[8,9] Fabrication of nano- and microfibers with similar properties has also showed promise in biomedical and composite applications. Mechanical characterization of materials at nano/microscale presents significant challenges due to the small forces and extensions that must be applied and measured. Some of the challenges have been addressed with recent advances in depthsensing nanoindentation technique, and in situ deformation studies inside an electron microscope. Quasi-static tensile mechanical properties of fibers with less than a few 10’s of μm in diameter have also been reported in literature.[10–12] However, the challenge is slightly different for soft and ductile materials in the form of small diameter fibers—below 100 µm— which require extremely small forces but can sustain large amounts of strain. In addition, polymeric and biological fibers often exhibit strain-dependent or time-dependent properties, leading to difficulties in interpreting their mechanical properties by conventional techniques. Unlike metals and ceramics, mechanical deformation in polymeric materials involves evolution of the molecular network.[13] The fundamental changes in the molecular structure have been observed through in situ x-ray diffraction and other spectroscopic methods.[14–16] However,
very little quantitative in
Data Loading...
