Chapter 16: Problem 29
Briefly describe laminar composites. What is the prime reason for fabricating these materials?
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Chapter 16: Problem 29
Briefly describe laminar composites. What is the prime reason for fabricating these materials?
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A continuous and aligned fiber-reinforced composite is to be produced consisting of 45 vol\% aramid fibers and 55 vol \(\%\) polycarbonate matrix; the mechanical characteristics of these two materials are as follows: The stress on the polycarbonate matrix when the aramid fibers fail is \(35 \mathrm{MPa}\) (5075 psi). For this composite, compute the following: (a) The longitudinal tensile strength (b) The longitudinal modulus of elasticity
A continuous and aligned fibrous reinforced composite having a cross-sectional area of \(970 \mathrm{~mm}^{2}\) (1.5 in. \(\left.^{2}\right)\) is subjected to an external tensile load. If the stresses sustained by the fiber and matrix phases are 215 MPa (31,300 psi) and \(5.38\) MPa (780 psi), respectively, the force sustained by the fiber phase is \(76,800 \mathrm{~N}\left(17,265 \mathrm{lb}_{\mathrm{f}}\right)\), and the total longitudinal composite strain is \(1.56 \times 10^{-3}\), determine the following: (a) The force sustained by the matrix phase (b) The modulus of elasticity of the composite material in the longitudinal direction (c) The moduli of elasticity for fiber and matrix phases
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. $$\begin{array}{lcc}\hline & \begin{array}{c}\text {Specific} \\\\\text {Gravity}\end{array} & \begin{array}{c}\text {Modulus of} \\\\\text {Elasticity (GPa)}\end{array} \\\\\hline \text { Copper } & 8.9 & 110 \\\\\text { Tungsten } & 19.3 &407 \\\\\hline\end{array}$$.
It is desired to produce an aligned carbon fiber-epoxy matrix composite having a longitudinal tensile strength of \(500 \mathrm{MPa}(72,500 \mathrm{psi})\). Calculate the volume fraction of fibers necessary if (1) the average fiber diameter and length are \(0.01 \mathrm{~mm}\left(3.9 \times 10^{-4}\right.\) in.) and \(0.5 \mathrm{~mm}\left(2 \times 10^{-2}\right.\) in.), respectively; (2) the fiber fracture strength is \(4.0\) GPa \(\left(5.8 \times 10^{5} \mathrm{psi}\right)\); (3) the fiber-matrix bond strength is \(25 \mathrm{MPa}\) (3625 psi); and (4) the matrix stress at composite failure is \(7.0 \mathrm{MPa}\) (1000 psi).
Cite one similarity and two differences between precipitation hardening and dispersion strengthening.
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