A large-particle composite consisting of tungsten particles within a copper matrix is to be prepared. If the volume fractions of tungsten and copper are 0.70 and 0.30, respectively, estimate the upper limit for the specific stiffness of this composite given the data that follow.

Specific Gravity Modulus of Elasticiy (GPa)
Copper 8.9 110
Tungsten 19.3 407

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Answer:

The upper limit for the specific stiffness of this composite is 19.6 GPa

Explanation:

Symbol for Copper is Cu while for Tungsten is W,

E = modulus of elasticity

V = Volume fraction of the materials

P = specific gravity of the materials

Let determine the combine maximum modulus of the materials using;

E = Ecu*Vcu + Ew*Vw

E = 110*0.3 + 407*0.7 = 318 GPa

Also, determine the combine specific gravity (P) of the materials

P = Pcu*Vcu + Pw*Vw

P = 8.9*0.3 + 19.3*0.7 = 16.2

The upper limit of the specific stiffness can be found by E/P = 318/16.2 = 19.6 GPa

The lower limit can be found from

{(Ecu*Vcu)/Pcu} + {(Ew*Vw)/Pw}

{(110*0.3)/8.9} + {(407*0.7)/19.3} = 18.5 GPa

The limit for the specific stiffness of this composite 18.5 to 19.6 GPa.

The upper limit for the specific stiffness of the composite from the given data is; 19.65 GPa

We are give;

Specific gravity of copper; ρ_cu = 8.9

Specific gravity of tungsten; ρ_tu = 19.3

Modulus of elasticity of copper; E_cu = 110 GPa

Modulus of elasticity of tungsten; E_tu = 407 GPa

Volume fraction of tungsten; V_tu = 0.7

Volume fraction of Copper; V_cu = 0.3

1) Upper limit for the specific stiffness;

Let us find the upper limit for the modulus of elasticity from the formula;

E_u = (E_cu × V_cu) + (E_tu × V_tu)

E_u = (110 × 0.3) + (407 × 0.7)

E_u = 317.9 GPa

Upper limit for the specific gravity is gotten from the formula;

ρ_u = (ρ_cu × V_cu) + (ρ_tu × V_tu)

ρ_u = (8.9 × 0.3) + (19.3 × 0.7)

ρ_u = 16.18

Specific stiffness = E_u/ρ_u

Specific stiffness = 317.9/16.18

Upper limit Specific stiffness = 19.65 GPa

2) Lower limit for the specific stiffness;

The lower limit is gotten from the formula;

Specific stiffness = ((E_cu × V_cu)/ρ_cu) + ((E_tu × V_tu)/ρ_tu)

Specific stiffness = (110 × 0.3/8.9) + (407 × 0.7/19.3)

Lower limit specific stiffness = 18.47 GPa

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