A tensile test specimen of a composite material consisting of two layers of wove

Question

A tensile test specimen of a composite material consisting of two layers of woven carbon fiber in an Epoxy matrix was instrumented with axial and transverse strain gages as shown in the figure. The sample was 0.635mm thick and 15.24mm wide. The sample was statically loaded in tension and the load and strains (axial and transverse) recorded. Recall that the units of mu is the actual strain value x 10 6. So 1234mu epsilon is the same as a strain of 0.001234. While most composite materials exhibit different (mechanical, thermal, optical, etc) properties in different directions in a specimen, you may assume in this exercise that the data were measured on a specimen whose elastic properties were approximately isotopic. For such a material any two (2) of following moduli-Young's ,modulus, E, shear modulus, mu or G, bulk modulus, B, or Poisson's ratio, v - will completely specify the elastic response of the material. Using the measured data, compute the Young's modulus and Poisson's ratio for this quasi-isotopic composite material.

Explanation / Answer

Youngs modulus is calculated from thefollowing formula.. from the defination of elastic modulus E = slope of load Vs extension(axial) curve /(width*thickness) Slope of load Vs. extension (along axial direction) curve can becalculated from given data =0.422 *10^6 therefore E= 43.6 Gpa similarly for shear modulus :: G = slope of load Vsextension(transverse) curve / (width*thickness) slope(transverse) =5.459 *10^6 therefore G=564.1 Gpa hence poisons ratio can be calculated fromE=2G(1+) =-0.961

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