3. A strip of chicken skin was excised for mechanical testing in tension. The initial dimension of the rectangular specimen was 30 mm long and 15 mm wide, with average thickness of 3 mm. The mechanical testing was conducted at a rate of 5 mm/sec. The following data were obtained: gauge length, mm 20 22 24.2 26.3 27.9 30.1 force, N 0 0.8 2.7 7.9 12.9 19.6 a. Calculate the engineering stresses and strain from the information given and plot the stress-strain curve. Assume that 5 mm of the specimen length is clamped by the testing grip at each end, such that the initial gauge length of the specimen is 20 mm.

You have been given the following set of data from a soil-geotextile friction test:   Normal stress (kPa) Peak shear strength (kPa) Residual shear strength (kPa) 17 20.2 13 35 31 22 70 52 39.5 140 94 74.5   (a) Plot the Mohr-Coulomb failure envelope (x-axis=normal stress; y-axis=shear stress) (b) Determine the peak friction angle,  and the residual friction angle, . (c) Determine the peak adhesion and the residual adhesion. (d) Calculate the fabric efficiency based on a soil friction angle of  = 35-degrees using the peak friction angle.   **HINT: the equation for efficiency of soil friction angle mobilization is: