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 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

4.51

B

25.45

C

26.45

D

27.45

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) Em + f Ef

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

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)

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

100 জন ছাত্রের সবাই হয় গণিতে না হয় ইংরেজীতে GPA 5 পেয়েছে। 80 জন গণিতে এবং 75 জন ইংরেজীতে GPA 5 পেলে কতজন ছাত্র উভয় বিষয়ে GPA 5 পেয়েছে?

A

5

B

25

C

55

D

70

______________ is used as a blending agent with epoxy resin to increase its glass transition temperature, modulus and tensile strength of epoxy resin.

A

Diamino diphenyl sulfone (DDS)

B

Diglycidyl ether of bisphenol A (DGEBA)

C

Polyether sulfone

D

Diethylene triamine (DETA)

If μ is the shear modulus of the matrix and V is the volume of the unconstrained hole in the matrix and the elastic energy does not depend on the shape of the precipitate, if so, calculate the elastic strain energy? (Assume the poissons ratio to be 1/3 and Misfit-Δ)

A

ΔG=4μΔ2/V

B

ΔG=4μ/Δ2*V

C

ΔG=4μΔ2*V

D

ΔG=4μΔ2 – V