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DETERMINATION OF ELASTIC CONSTANTS OF NATURAL MICA

Pages: 28 – 39

Mohammed N. Alghamdi, Lidvin Kjerengtroen, Jon Kellar and William Cross

Abstract:

The laminate structure of mica is very complex, mostly due to its anisotropic behavior in the direction of the property C33. Therefore, cutting mica sample is always challenging, particularly when relatively thick samples are desired. Thinner samples are relatively easy to cut and suffer little damage. However, in thick samples much damage can occur. This damage consists of cracks and boundary debonding between mica layers causing the properties to vary as a function of thickness. Therefore, the overall objective of this research is to determine the Young’s modulus of natural muscovite mica using different thicknesses. Using tensile tester (Q 800 DMA), the Young’s modulus of muscovite mica was found to be 178.3 GPa for 20 μm thick samples. This modulus agrees well with the literatures values for mica. The modulus decreased gradually when the sample thickness increased, reaching a mean value of 115 GPa for 94 μm thick samples. This indicates a decrease of about 35 % Young’s modulus when the thickness increased by ~79 %. Cutting muscovite with a specifically designed pressure fixture shows improvement in Young’s modulus along the direction of the property C11, compared with the hand-cut fully exfoliated procedure. In addition, Young’s modulus was not improved using pressure fixture cut compared with hand-cut samples. From these results it can be concluded that, the weak bonding which hold the layers together, could carry and/or transmit loads and is a key element to the overall stiffness of mica.

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