A glass reinforced polymer composite comprises of 35 volume % glass fiber and 65 volume % of polymer resin. The elastic moduli of glass and polymer resin are respectively 70 GPa and 3 GPa. The elastic modulus of the composite (in GPa) under iso-strain state is

A glass fibre reinforced epoxy composite is made with 60 wt.% unidirectional continuous glass fibres. The elastic moduli of the glass fibre and the epoxy matrix are 72.5 and 2.4 GPa, respectively. What is the elastic modulus of this composite along the fibre direction, in GPa? The densities of glass fibre and epoxy are 2.58 g/cm³ and 1.14 g/cm³, respectively

A

10.5

B

20.5

C

30.5

D

4.5

Graphite fibres are used to make undirectional Al-matrix composites. Young's modulus of graphite and aluminium are 400 GPa respectively. If a composite contains 60 volume % of fiber and is loaded along the fiber direction, the Youngs Modulus of the composite is . . . . . . . . GPa.

A

60

B

164

C

264

D

364

A polymer matrix composite is reinforced with long continuous ceramic fibers aligned in one direction. The young's moduli of the matrix and fibers are Em and Er respectively and the volume fraction of the fibers is f. Assuming iso-stress condition, Young's modulus of the composite Ec in a direction perpendicular to the length of fibers, is given by the expression

A

Ec = (1 - f) E<sub>m</sub> + f E<sub>f</sub>

B

Ec = f Em + (1 - f) Er

C

$$\frac{1}{{Ec}} = \frac{{\left( {1 - f} \right)}}{{{E_m}}} + \frac{f}{{Ef}}$$

D

$$\frac{1}{{Ec}} = \frac{f}{{{E_m}}} + \frac{{\left( {1 - f} \right)}}{{Ef}}$$

The modulus of rigidity and the modulus of elasticity of a material are 80 GPa and 200 GPa. What will be the Poissons ratio of the material?

A

0.25

B

0.30

C

0.40

D

0.50

Calculate the shear modulus for steel in GPa, if given that young modulus is 215 GPa and possion’s ratio is 0.33?

A

40 GPa

B

50 GPa

C

80 GPa

D

100 GPa

If the first two statements are true, the third statement is :
I. Oat cereal has more fiber than corn cereal but less fiber than bran cereal.
II. Corn cereal has more fiber than rice cereal but less fiber than wheat cereal.
III. Of the three kinds of cereal, rice cereal has the least amount of fiber.

A

true

B

false

C

[C. uncertain

Which of the following relationships is correct for relating the three elastic constants of an isotropic elastic material (where, E = Young's modulus, G = Modulus of rigidity or shear modulus v = Poisson's ratio)?

A

E = 2G (1 + v)

B

E = G (1 + v)

C

$${\text{E}} = \frac{{{\text{G}}\left( {1 + {\text{v}}} \right)}}{2}$$

D

E = 2G (1 + 2v)

E, G, K and μ elastic modulus, shear modulus, bulk modulus and Poisson’s ratio respectively. To express the stress strain relations completely for this material, at least __________

A

E, G and μmust be known

B

E, K and μmust be known

C

Any two of the four must be known

D

All the four must be known

Resin P, on further heating turns into completely cross-linked resin Q, which is totally insoluble and infusible. Resin P is slightly heat fusible and insoluble in alkalis and alcohols but partly soluble in acetone. What are the names of resin P and Q?

A

resol and resitol

B

resitol and resite

C

resol and resite

D

none of the mentioned

After 3 semesters in college , jim has a 3.0 GPA. What GPA must jim attain in his fourth semesters if he wishes to raise his GPA to a 3.1 ?

A

2.7

B

3.1

C

3.3

D

3.4