Homework 5

Question 6. Calculate the average molecular weight Mm for a thermoplastic that has the following weight fractions fi for the molecular weight ranges listed: Molecular Weight _fi 0.01 Molecular Weight Range (g/mol) 20,000-25,000 25,000-30,000 30,000-35,000 35,000-40,000 Range (g/mol) fi 0-5000 0.19 5000-10,000 0.04 0.21 0.15 10,000-15,000 15,000-20,000 0.16 0.17 0.07

d) A carbon fibre reinforced composite is made using a volume fraction of 77% carbon. The material properties of the constituent materials are listed below: E (GPa) Strength (MPa) 1500 900 Carbon fibre Epoxy 60 3 The composite is loaded in tension and a Young's modulus of 12.9GPa is measured. Is this the maximum modulus the composite can experience? Explain your answer. For a modulus of 12.9GPa, can the strength be estimated? Explain your answer. Relevant formulae: (4 marks) 1 E Vf E₁ 'm Em E = EfVf + EmVm o = ofV₁ + 0mVm +

Calculate the percentage increase in the mechanical properties of reinforced nylon from the data given in Fig 10.19.

STRESS STRAIN Typical for thermosets Typical for thermoplastics Q/Interpret the following drawing

Polymeric materials are liable to creep at room temperature, stress and time of loading, which one of the following statements is correct? a. the longer the time, the creep strain increase. b. The higher the temperature, the higher the creep limit. c. Reduce the stress increases the strain. d. Increase the temperature increases the creep strain.

i. Calculate the tensile modulus of elasticity of a unidirectional Kevlar-49 fibers epoxy composite material that contains 63% by volume of Kevlar 49 fibers and is stressed under isostrain conditions. The Kevlar 49 fibers have a tensile modulus of elasticity of 189.8 GPa and the epoxy matrix a tensile modulus of elasticity of 3.8 GPa. ii. If the tensile strength of the Kevlar 49 fibers is 3.8 GPa and that of the epoxy resin is 75.9 MPa, calculate the tensile strength of the composite material in Q3b(i). Calculate the fraction of load carried by the Kevlar 49.

Question 3 The diameter of an extruder barrel is 65 mm and its length is 1.75 m. The screw rotates at 55 rev/min. The screw channel depth is 5.0 mm, and its flight (helix) angle is 18°. The head pressure at the die end of the barrel is 5x10° Pa. The viscosity of the polymer melt is given as 100 Pa-s. Calculate the volume flow rate of polymer in the barrel. The drag flow is given by the equation: Qa = 0.5 n² D² N d̟ sinp cosp The back pressure flow is given by the equation: Pn D dễ sin²4 Qb 127L The details of the extruder screw are given in figure 3.1 W. channel width Perpendicular Pitch Helix ( p angle () D Channel depth de |Axial |light| width Axial channel width Perpendicular flight -Direction of mass flow- Figure 3.1. Schematic illustration of a typical "Archimedean" extruder screw. width Root diameter diameter

Can someone assist me please? Thanks.

The σ - ε diagram for elastic fibers is shown. (Figure 1) Figure 385 σ(MPa) 77 < 1 of 1 €(mm/mm) 1 2 2.25