What are the main differences between sheet molding

Question

Part A-

1. Create a table listing in detail the potential advantages and disadvantages of composite materials?

2. What affect does temperature and moisture have on composite materials and constituents (elevated and cold)?

3. Describe typical issues that lead to composite delaminations during fabrication, assembly and in-service?

Part B-

1. What are the main differences between Sheet Molding Compounds (SMC) and Bulk Molding Compounds (BMC)?

2. Describe the difference between a thermoset and thermoplastic resin.

3. What is the Glass Transition Temperature (Tg) as it pertains to a thermoset resin?

4. Describe why the through-the-thickness or z-directional properties of a composite are low.

5. The following data were obtained in a resin burn-off test of an E-glass-polyester sample:

Weight of Empty Crucible = 10.1528g

Weight of crucible + sample before burn-off = 10.5219g

Weight of crucible + sample after burn-off = 10.3221g

Calculate the fiber weight fraction, the fiber volume fraction, and the density of the composite sample. Assume ρf = 2.54 g/ml and ρm = 1.25 g/ml. Do you expect the calculated value to be higher or lower than the actural value?

6. Determine the weight and cost of pre-preg required to produce hollow composite tube (outside diameter = 50mm, wall thickness = 5mm and length = 4m) if it contains 60 volume percent AS-4 carbon fibers (at $60/kg), in an epoxy matrix (at $8/kg). The tube is manufactured by wrapping the pre-preg around a mandrel, and the cost of pre-pregging is $70/kg.

7. Calculate the longitudinal modulus, tensile strength, and failure strain of a unidirectional continuous fiber composite containing 60 vol % of T-800 carbon fibers (E_f = 294GPa and σ_fu = 5.6GPa) in a toughened epoxy matrix (E_m = 3.6GPa, σ_my = 105MPa, and ε_mu = 3.1%). Compare these values with the experimentally determined values of E_L = 162 GPa, σ_Ltu = 2.94GPa, and ε_Ltc = 1.7%. Suggest three possible reasons for the differences. What fraction of load is carried by the fibers in this composite?

8. The material of a tension link is changed from Ti-6A1-4V (aged) titanium alloy to a unidirectional continuous GY-70 carbon fiber-epoxy. Calculate the volume fraction of GY-70 fibers required in the composite link to match the modulus of the titanium alloy. Also, estimate the tensile strength of the composite link and compare its strength-weight ratio with that of the titanium alloy.