a b s t r a c tAligned multi-walled carbon nanotube (CNT) sheets produced from aligned CNT arrays were used to develop high volume fraction CNT/epoxy composites. Stretching and pressing techniques were applied during CNT sheet processing to straighten the wavy CNTs and to enhance the dense packing of CNTs in the sheets. Raman spectra measurements showed better CNT alignment in the CNT sheets and the composites after stretching and pressing. Aligned CNT/epoxy composites with CNT volume fraction up to 63.4% were developed using hot-melt prepreg processing with a vacuum-assisted system. Stretching and pressing of the CNT sheets enhanced the mechanical properties of high volume fraction CNT/epoxy composites considerably. Stretching and pressing increased tensile strength of the composites by 32% and elastic modulus of the composites by 27%. Applying stretching and pressing is effective for production of superior CNT sheets with high alignment and dense packing of CNTs, thereby supporting the development of high-performance CNT composites.

Path integral, domain integral and least squares methods for evaluating J-integral from measured displacement fields for a power-law hardening material are described in this paper. The values of the J-integral are evaluated by applying the path and domain integral methods to the displacement fields obtained by elastoplastic finite element analysis and the displacement fields obtained through the measurement using digital image correlation. Results show that the values obtained by the domain integral method are slightly better than those by the path integral method, because the domain integral method efficiently uses the full-field measurement data. The values of the J-integral are also evaluated by the least squares method with the Hutchinson, Rice, and, Rosengren displacement fields. Results show that the J-integral can be obtained by the least squares method simply and easily without any calculation of the integration. The J-integral values obtained by the least squares method agree well with the values obtained using other methods. Because J-integral can be evaluated easily by any method described in this paper, it is expected that these methods are applicable to various fracture problems during experimental evaluation of structural components.

Background/purposeThis study proposes a technique for visualizing the effect of facial massage using stereo‐image correlation with melanin pigment.MethodIn this method, the melanin pigment of a subject's face is made visible by using an ultraviolet light and utilized as a random pattern for stereo‐image correlation. Stereo‐pair images of the face with the melanin pigment before and after facial massage are recorded using a desk‐sized measurement equipment. Then, the deformation of the face by the massage can be obtained based on the principle of stereovision. The effectiveness of the proposed method is demonstrated by applying it to the massage effect evaluation of eight subjects (females in their 40s).ResultsThe results show that the massage effect can be visualized from the displacement and strain distributions across the face obtained by the proposed method. In addition, it is observed that the face is displaced significantly by the massage and individual differences between the subjects can be captured.ConclusionThe proposed method is effective for evaluating the effect of a facial massage when the painted pattern disappears due to the applied cream during the massage.

Strain measurements around the eye during the blink are performed for four human subjects in order to investigate the relationship between the wrinkle formation with aging and the strains by daily motion. In addition to the strain measurement, the moisture content, the flexibility and the elasticity of the skin surface are measured for investigating the skin condition. For observing the wrinkle formed on the facial skin, the replicas of the skin surfaces are also collected. Results show that the relationship between the wrinkle and the strain distribution at the inner corner of the eye is different from that at the corner of the eye. The results indicate that different methods for the corner of the eye and the inner corner of the eye are required for avoiding the wrinkle formation.

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In this study, a method for evaluating a fracture parameter, J-integral, for an interface crack from the displacement fields under thermal deformation is developed for studying the fracture behavior of an interface crack in an actual electronic component. First, the displacement fields around an interface crack tip are measured using digital image correlation (DIC). Second, the displacement gradient and strain are determined from the displacement fields using a finite element smoothing technique on the domain of integration. Then, the stress components are determined from the strains using the elastic-plastic relations with the incremental strain theory and the each material property. Finally, the J-integral value is determined by the numerical integration on the domain of integration. The effectiveness of this evaluation method is demonstrated by applying this method to the displacement fields obtained from the elastic-plastic finite element analysis.

A super pressure balloon (SPB) is an aerostatic balloon that can fly at a constant altitude for an extended period. Japan Aerospace Exploration Agency (JAXA) has been developing a light-weight, high strength balloon made of thin polyethylene films and diamond-shaped net with high tensile fibers. Previous investigations proved that strength requirements on SPB members are satisfied even though the net covering the SPB sometimes becomes damaged during the inflation test. This may be due to non-uniform expansion, which causes stress concentration, however, no method exists to confirm this hypothesis. In this study, we tested a new method called Simplified Digital Image Correlation method (SiDIC) to check if it can measure the displacement of the SPB by using a rubber balloon. After measuring the measurement accuracy of the Digital Image Correlation method (DIC) and SiDIC, we applied both DIC and SiDIC to a rubber balloon covered just with the net. Interestingly, SiDIC entailed a smaller amount of data but could measure the deformation more accurately than DIC. In addition, assuming the stress concentration, one part of the net was bonded to the balloon to restrict the deformation. SiDIC properly identified the undeformed region.

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