Experimental characterisation of the mechanical properties and microstructure of Acrocomia mexicana fruit from the Yucatan Peninsula in Mexico

A study of the mechanical properties and microstructure at different drying conditions of the Cocoyol fruit endocarp of Acrocomia Mexicana palm found in the Yucatan Peninsula in Mexico was performed. Quasi-static uniaxial compression was carried out on endocarp samples. The experimental results showed that the fruit exhibited an average peak force and displacement at failure of 4.23 kN and 2.43 mm, respectively. The average energy absorbed by the fruits before failure was 6.06 J. Optical and scanning electron microscopy of cross-sections of the equatorial region revealed that the endocarp has complex hierarchical structure. The micrographs showed that the structure is made of bundles of randomly oriented tubes and bubble-like cells, showing entangled network of hollow micro channels, which are in the order of tens of microns. The results and the microstructure presented herein encourage further research for bioinspired man-made materials.Australian Research Council (ARC) Centre of Excellence for Design in Light Metals (CE0561574). Consejo Nacional de Ciencia y Tecnologia, CONACyT (CB-2008-01, reg. 101608)

Effects of heat treatment and strain rate on the microstructure and mechanical properties of 6061 Al alloy

In the present work, the effects of heat treatment and strain rate on mechanical behaviour and microstructure evolution of aluminium alloy (AA) 6061 have been investigated. The micro-crack initiation and crystallographic texture evolution are obtained from scanning electron microscope (SEM) and electron back-scatter diffraction (EBSD) experiments. Quasi-static and high strain rate compression tests are conducted on AA6061 specimens that underwent two different heat treatments: the as-received material with the original T6 heat treatment and the heat treated and artificially aged (HT) specimens. For the high strain rate compression (~2000 s-1 and ~4000 s-1) tests, the split Hopkinson pressure bar apparatus is used. It is observed that the additional heat treatment has significantly reduced the yield strength of the material. Furthermore, EBSD results show that the higher the applied strain rate is, the less significant change will happen to the texture. SEM images show that, for both T6 and HT specimens, the number and size of micro-cracks in the dynamic compressed specimens are smaller than in the quasi-static deformed specimen. Therefore, the strain rate is considered to be the dominant factor in forming micro-cracks.Australian Research Council through Centre of Excellence for Design in Light Metals (CE0561574). Discovery Projects (DP130101291 and DP140100945). LIEF Project (LE100100045). The National Natural Science Foundation of China through Grant No. 11232003