Part A

1. A composite has Ef =100 GPa, Em = 10 GPa. Calculate the percentage increase in load

carrying capacity of a uniaxial bar when the fiber increased from 70% to 80%.

2. Write the general compliance matrix for a fiber reinforced materials.

3. What are the applications of various composites in aircraft industry?

4. How does one evaluate the material properties along arbitrary directions in a fiber

reinforced lamina knowing the properties along principal material directions?

5. Name any two matrix materials with fibers used in fiber reinforced laminates.

6. Classify thermo setting polymers.

7. Show that for an orthotropic material Q66 = C66. Explain why?

8. What are the values of stiffness matrix C22 and C12

9. {ε} = [S] {σ} ,where{ε}= strain matrix, [S]= compliance matrix, {σ}=stress matrix. Give

the compliance matrix for an orthotropic lamina and isotropic lamina.

10. An isotropic lamina has E= 100 kN/mm2 and ν = 0.25. Determine the reduced stiffness

matrix (Qij) and reduced compliance matrix (Sij).

Part B

1. Define stiffness and compliance matrix for an anisotropic materials and explain how it is

transformed to orthotropic, monoclinic and isotropic materials.

2. Derive the expression for stiffness matrix and compliance matrix for an angle ply lamina

using generalized Hooke’s law.

3. Explain about the fiber matrix interactions in a unidirectional lamina with a suitable

sketch.

4. Derive the number of elastic constants for the following materials:

a. Anisotropic

b. Orthotropic

c. Isotropic

5. What is rule of mixtures? Derive an expression in terms of volume fraction to determine

the density of composites.

6. With the help of a line sketch explain the inter laminar stresses of a composite laminate.

7. Explain the mechanics of load transfer from matrix to fiber.

8. Derive the expression to compute the elastic constants of a lamina.

9. Discuss the variation of lamina properties with orientation.

10. Derive the expression to determine the following properties of unidirectional composites:

a. Shear modulus

b. Poisson’s ratio

11. Derive the material stiffness matrix ‘Q’ for plane fiber reinforced lamina starting from the

fundamentals.

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12. Write a detailed account about the various types of fibers, which are generally used in

composite materials.

13. Explain the difference between thermosetting and thermoplastic matrix materials.

14. A graphite / epoxy unidirectional lamina is subjected to σl= 2 MPa, σt = 3 MPa, τlt=4

MPa and material constants are El= 181 GPa, Et= 10.3 GPa, Glt= 7.17

GPa, νlt=0.28. Determine the stiffness matrix and compliance matrix.

15. Using elasticity approach, obtain the expressions for upper bound and lower bound on

apparent Young’s modulus for anisotropic composite materials.

16. A lamina with 30 fiber orientation to the x axis is subjected to σx= 20 MPa, σy = 15

MPa, τxy10 MPa and material constants are El= 54 GPa, Et= 18 GPa, Glt=

8.5 GPa, νlt=0.25. Determine the stiffness matrix and compliance matrix.

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