Hybridization and yarns configuration effects on flexural dynamic and static properties of pultruded hybrid kenaf/glass fiber composites

Six different hybrid composites with various hybrid fiber mixing ratio were fabricated using the pultrusion technique. The effect of fibers hybridization and fibers configuration with respect to the loading axis were studied on flexural dynamic and static properties. In low fiber mixing ratio of about 0.09, the radial configuration of kenaf yarns in the core region had no significant effect on dynamic flexural modulus. The radial configuration of the kenaf yarns in the core of the composites and bilateral configuration of the glass yarns in the shell region showed a considerable effect on damping factor. The bilateral configuration of glass yarns in the shell region indicated a noticeable effect on the static flexural modulus, strength and the strain at break. The regression analysis showed a significant relationship between the static and dynamic modulus, and the dynamic flexural modulus explained 98% of the variability of the static flexural modulus

Numerical modeling in quantitative ultrasonic tomography of standing trees

International audienceThe aim of this project is to develop an ultrasonic device for parametric imaging of standing trees. The device is designed to perform both transmission and reflection measurements that can be therefore used for quantitative tomographic imaging. It allows various automatic acquisitions, since the angular position of the transducers could be adjusted. This makes possible to scan the wave propagation occurring in all directions inside the medium. The associated electronic set-up allows mainly measuring the slowness (and therefore the velocity) and the attenuation of the ultrasonic waves. Tomograms were computed by fast algebraic algorithms: (1) using the filtered backprojection algorithm with fan beam geometry, (2) using a new algorithm that we are developing based on a "layer-stripping" method. Our first numerical results on an academic and realistic phantom of tree are presented in this paper