Ever-decreasing length scales in manufacturing technology present a serious challenge for materials characterization. When the diameters of fiber materials are reduced from micrometers to nanometers, there appear several amazing characteristics such as very large surface area to volume ratio, flexibility in surface functionalities, and superior mechanical performance compared with any other known form of the material. Techniques for mechanical characterization of such nanofibers, referring to fibers with a diameter less than 1 micron, are discussed in this presentation. First, a direct comparison of nanoindentation with atomic force acoustic microscopy (AFAM) is made on micron-sized glass fibers. The results obtained from the two techniques are analyzed and compared. It is shown that both techniques give the same reduced modulus for these fibers. AFAM is then applied to randomly-oriented zirconia nanofibers embedded in epoxy. For these materials, nanoindentation is no longer an option because the indenter tip is much larger than the length scale of the fibers. The use of several reference materials, including fused silica, single-crystal silicon, and sapphire, are also discussed. In addition to the quantitative measurements using AFAM, contact stiffness images of these materials are also presented. The results are anticipated to have a positive impact on nanoscale mechanical characterization.
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