Carbon – Carbon bond distance:-0.15nm
Material Surface Energy:- U = 50Mj/m^2
Elastic Modulus: - E = 1 Tpa
b) Sketch a Lennard-Jones curve for the carbon-carbon bonds in the carbon fiber and show a comparable Lennard-Jones curve for copper fibers where the strength and elastic
Modulus of the copper is lower than for carbon. Clearly indicate the differences between
the two materials. [9 Marks]
In this process the reinforcing of the carbon fibers can be enhance. This process is start with pulling the fibers in to the electrolyte bath. In this process the chemical is react with surface of fiber and rough surface. This can increase the surface area of filament for interfacial fiber. In the next stage, the coating is applying on the whole surface of the fiber. Which is 0.5 to 5 % weight of fiber. When the sizing dries, the long process is complete.
(b) The composite uses the carbon fibres with 50% in a 45° and 50% in a -45° orientation to improve
fatigue resistance. An epoxy with an elastic modulus of 1 GPa and a low-grade carbon fibre with an
elastic modulus of 200 GPa are used in the composite.
1 .State the krenchel equation that can be used to to predict the elastic modulus of the composite.
= proportion of total fibre content
? = angle of fibers
= composite efficiency factor (Krenchel)
2. Calculate Orientation Factor For Composite.
Layup = (+45/-45)
η = Cos4θ
= Cos4 45°
η = 0.25
Laminate in X-direction
= (1× 0.25)
Laminate in Y-direction
= (1× 0.25)
3.(ili) Calculate the resultant elastic modulus of the composite assuming the length efficiency
factor is 0.8. [4 Marks]
Ef = 200 GPa
Em= 1 GPa
Vf = 0.8
Ex = (0.25 × 200×0.8) + (1×0.2)
Ex = 40 + 0.2 = 40.2 GPa
Ey = (0.25 × 200×0.8) + (1×0.2)
Ey = 40 + 0.2 = 40.2 GPa
4. Suggest how the resultant composite elastic modulus would vary compared to your answer
in (iii) for fibre orientation approaching Voigt and Reuss conditions.
Ec= 4.9 Gpa
Voigt analysis is used for the linear analysis. There is no orientation effect on the results. But the Krenchel allow us to do the calculation using orientation of the ply.
The simply supported beam in Fig. T2 carries two concentrated loads.
(a) Derive the expressions for the shear force and the bending moment for each segment of the beam.
(b) Sketch the shear force and bending moment diagrams.
S.F. Calculations –
S.F. at A ( Just LHS ) = 0.0
-- S.F. at A ( Just RHS ) = + 18 kN
-- S.F. at B ( Just LHS ) = + 18 kN
-- S.F. at B ( Just RHS ) = + 18.0 – 14 = 4 KN
-- S.F. at C ( Just LHS ) = +4 KN
-- S.F. at C ( Just RHS ) = + 4 – 28.0 = - 24 KN
-- S.F. at D ( Just LHS ) = -24 KN
-- S.F. at D ( Just RHS ) = -24 + 24 = 0.0 KN S.F.D. will be as shown in fig.
B.M. Calculation –
-- B.M. at A = 0.0 KN-m.
-- B.M. at B = + ( 18 x 2 ) = + 36 kN-m.
-- B.M. at C = + ( 18 x 5 ) – ( 14 x 3 ) = + 48 kN-m.
-- B.M. at D = 0.0 kN- m. The B.M.D. will be as shown in fig.
The main components of the artificial hip are the femoral stem that is fitted into the bone, the ball attached to the stem and the acetabular cup that is fixed into the pelvis. The property constrains on the materials to be used for these elements are very strict because of chemical and mechanical complexity of the hip joint.
(a) What are the main material requirements for hip implants? Briefly justify each point. [10 Marks]
< >High biocompatibility:-Nonmagnetic:-The material should be non-Magnetic. In the many time of the life human can come in interaction with the Magnetic Resonance Imaging (MRI). If a person done the transplant before. And this transplant is magnetic, then this situation can create the problem .Because of MRI the transplant gets heated and may change its position, so the material should be nonmagnetic.The surface femoral stem should be bioactive in terms of osteointegration :- It is a important that when transplant has done ,the living bone should accept the transplant and make a strong bond. So the material has to be osteointegration in nature Adequate mechanical :- The material has to good mechanical properties like high young modulus. Good yield strength, The material should be optimum amount of ductile. The tensile strength should be good enough. Very low toughness value. The material has high hardness so that the wear and tear should be low. The fatigue strength is good.The surface of the layer has high modulus of elasticity. The structure can be a porous structure.The layer of the implant or free surface does not have surface defects like scratches ,cracks, or any other defect.The surface morphology of the implant should be fine. If the surface is expose to the load then it is very fine .Or if it is for stem then the rough surface can be used.The implant should be chemically stable. There is not defect at the microscopic level like interstitial defect of point defect.The implant should have high quality but it should not be deal with the price. The price should be economical.Materials selection of femoral stem componentMaterials selection of femoral head and acetabular cup componentsMetal-on-metalCeramic-on-ceramic
(a) The effective (von Mises) stress for this implant. [11 Marks]
Material compressive yielding Strength = 30 MPa ,The Tresca stress is 20.4 Mpa so Material Safe in compressive yielding.
b) The factor of safety against yield. [3 Marks]
The Factor of safety can be found by yielding compressive strength of material to Tresca stress.
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