(Solved): (a) Describe how to determine the onset of necking based on the nominal stress strain curve of a c ...

(a) Describe how to determine the onset of necking based on the nominal stress strain curve of a cold-drawing polymer. Describe the Considère construction, and derive the relevant equations for determining the onset of necking based on the true stress strain curve. (7 marks) (b) In your own words, briefly describe the phenomenon of viscoelasticity. Contrast the manner in which stress relaxation and viscoelastic creep tests are conducted. (3 marks) (c) Briefly explain how each of the following influences the tensile modulus of a semicrystalline polymer and why: molecular weight, degree of crystallinity, deformation by drawing, annealing of an un-deformed material, and annealing of a drawn material. (7 marks) (d) Describe the functions of different components in composite materials, and discuss about their characteristics in terms of the mechanical properties. (4 marks) (e) A continuous and aligned glass fiber-reinforced composite consists of 40 vol\% glass fibers having a modulus of elasticity of \( 69 \mathrm{GPa} \) and 60 vol\% polyester resin that, when hardened, display a modulus of \( 3.4 \mathrm{GPa} \). Compute the modulus of elasticity of this composite in the longitudinal and transverse directions. (4 marks)