Techniques and applications of SEM moire and AFM moire

The SEM moiré method can obtain deformation measurement and microscopic observation simultaneously. Some drawbacks exist: (1) the requirement of a vacuum environment (2) the reinforcement effect of grating material, and (3) the multiple steps of grating fabrication. To reduce these drawbacks several new techniques were developed. The AFM moiré method allows deformation measurement in a normal laboratory environment. A new grating technique, direct electron beam deposition, was developed. This technique deposits a carbonaceous grating on a specimen surface. The thickness of this carbonaceous grating is reduced to 8 nm instead of 100 nm of PMMA grating, minimizing the reinforcement effect. A total of six SEM moiré methods were produced by combining three viewing techniques with two grating fabrication techniques. The sensitivity of the SEM moiré method is improved from 0.2% to 0.02% or even higher if a higher frequency of grating is used. The SEM moiré method was applied to the deformation measurement of carbon fiber reinforced composites. Another application is the local strain measurement of a two-phase polymer under the stress relaxation experiment. The interface shifting is observed and the local strain is measured by the SEM moiré method simultaneously. Accordingly, an analytical solution of dynamic mechanical properties based on the rule of mixtures was derived. The dynamic mechanical analysis (DMA) was conducted on two-phase polymer specimens with different volume fractions in parallel and serial loading configurations. It seems that the analytical solution does not predict the experimental data of a two-phase polymer in serial loading configuration. On the other hand, the dynamic mechanical properties of specimens in parallel loading configuration match very well with the analytical solution.