Engineering Materials and Their Applications: Composites
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Questions and Answers

What are composites?

Artificially produced multiphase materials with desirable combinations of the best properties of the constituent phases.

How are large particle composites defined?

Polymeric materials with fillers, improving properties and/or replacing some polymer volume with a less expensive material.

What is the rule of mixtures in composites?

The behavior of a two-phase composite is influenced by the volume fraction of the constituent phases, with mechanical properties being enhanced with increasing particulate content.

How are composites classified in this discussion?

<p>Composites were classified as particle-reinforced, fiber-reinforced, and structural.</p> Signup and view all the answers

What is the function of the matrix in composites?

<p>The matrix is continuous and completely surrounds the dispersed phase.</p> Signup and view all the answers

Provide an example of a large particle composite.

<p>Concrete, composed of cement (the matrix) and sand and gravel (the particulates).</p> Signup and view all the answers

What does the critical fiber length (lc) depend on?

<p>fiber strength, diameter, and fiber-matrix bond strength/matrix shear yield strength</p> Signup and view all the answers

What is the influence of fiber orientation and concentration on fiber-reinforced composites?

<p>significantly impact the strength and properties of fiber-reinforced composites</p> Signup and view all the answers

What is the total load sustained by the composite in the case of elastic behavior under longitudinal loading?

<p>the sum of the loads carried by the matrix phase Fm and the fiber phase Ff</p> Signup and view all the answers

What are the two possible extremes in fiber orientation for fiber-reinforced composites?

<p>parallel alignment of the longitudinal axis of the fibers in a single direction and totally random alignment</p> Signup and view all the answers

What is the influence of the interfacial bond between the fiber and matrix phases on the mechanical properties of a fiber-reinforced composite?

<p>crucial for load transmittance, which ceases under stress, resulting in matrix deformation</p> Signup and view all the answers

What does the modulus of elasticity versus volume percent tungsten graph represent?

<p>a composite of tungsten particles dispersed within a copper matrix</p> Signup and view all the answers

What is the effect of increasing fiber length on fiber reinforcement in a fiber-reinforced composite?

<p>the fiber reinforcement becomes more effective</p> Signup and view all the answers

What is the influence of the mechanical properties of a fiber-reinforced composite on the fiber's properties and load transmitted by the matrix phase?

<p>The mechanical properties depend on the fiber's properties and the load transmitted by the matrix phase</p> Signup and view all the answers

What is the significance of critical fiber length (lc) for composite material strengthening and stiffening?

<p>Critical fiber length (lc) is crucial for composite material strengthening and stiffening</p> Signup and view all the answers

What are the factors that influence the mechanical properties of continuous and aligned fiber composites under longitudinal loading?

<p>fiber and matrix phase stress-strain behaviors, phase volume fractions, and load direction</p> Signup and view all the answers

Composites are artificially produced multiphase materials having desirable combinations of the best properties of the constituent phases. Usually, one phase (the matrix) is continuous and completely surrounds the other (the dispersed phase). In this discussion, composites were classified as ______, fiber-reinforced, and structural.

<p>particle-reinforced</p> Signup and view all the answers

Large-particle composites are polymeric materials with fillers, improving properties and/or replacing some polymer volume with a less expensive material. Concrete is a common example, composed of cement (the matrix) and sand and gravel (the ______).

<p>particulates</p> Signup and view all the answers

The behavior of a two-phase composite is influenced by the volume fraction of the constituent phases, with mechanical properties being enhanced with increasing particulate content. Two mathematical expressions predict that the elastic modulus should fall between ______ and lower bounds.

<p>upper</p> Signup and view all the answers

The behavior of a two-phase composite is influenced by the volume fraction of the constituent phases, with mechanical properties being enhanced with increasing particulate content. Two mathematical expressions predict that the elastic modulus should fall between upper and ______ bounds.

<p>lower</p> Signup and view all the answers

Composites are artificially produced multiphase materials having desirable combinations of the best properties of the constituent phases. Usually, one phase (the matrix) is continuous and completely surrounds the other (the dispersed phase). In this discussion, composites were classified as particle-reinforced, ______, and structural.

<p>fiber-reinforced</p> Signup and view all the answers

Composites are artificially produced multiphase materials having desirable combinations of the best properties of the constituent phases. Usually, one phase (the matrix) is continuous and completely surrounds the other (the dispersed phase). In this discussion, composites were classified as particle-reinforced, fiber-reinforced, and ______.

<p>structural</p> Signup and view all the answers

The modulus of elasticity is denoted by E and the volume fraction is denoted by V, whereas the subscripts c, m, and p represent composite, matrix, and particulate phases. Figure 1.2 Modulus of elasticity versus volume percent tungsten for a composite of tungsten particles dispersed within a copper ______.

<p>matrix</p> Signup and view all the answers

Critical fiber length (lc) is crucial for composite material strengthening and stiffening, influenced by fiber strength ((\sigma_f^*)), diameter (d), and fiber-matrix bond strength/matrix shear yield strength (τc). Figure 1.4 Stress–position profiles when fiber length l (a) is equal to the critical length lc, (b) is greater than the critical length, and (c) is less than the critical length for fiber-reinforced composite that is subjected to a tensile stress equal to the fiber tensile ______.

<p>strength</p> Signup and view all the answers

As fiber length l increases, the fiber reinforcement becomes more ______.

<p>effective</p> Signup and view all the answers

Continuous and Aligned Fiber Composites Tensile Stress–Strain Behavior—Longitudinal Loading The mechanical properties of this type of composites depend on factors like fiber and matrix phase stress-strain behaviors, phase volume fractions, and load ______.

<p>direction</p> Signup and view all the answers

The properties of an aligned composite are highly ______, influenced by measurement direction. Figure1.6 (a) Schematic stress–strain curves for brittle fiber and ductile matrix materials. Fracture stresses and strains for both materials are noted. (b) Schematic stress–strain curve for an aligned fiber–reinforced composite that is exposed to a uniaxial stress applied in the ______ of alignment.

<p>anisotropic; direction</p> Signup and view all the answers

Elastic Behavior—Longitudinal Loading The total load sustained by the composite Fc is equal to the sum of the loads carried by the matrix phase Fm and ______.

<p>t</p> Signup and view all the answers

The interfacial bond between the fiber and matrix phases is crucial for load transmittance, which ceases under stress, resulting in matrix ______.

<p>deformation</p> Signup and view all the answers

Figure 1.5 Schematic representations of (a) continuous and aligned, (b) discontinuous and aligned, and (c) discontinuous and randomly oriented fiber–reinforced ______.

<p>composites</p> Signup and view all the answers

Influence of fiber orientation, concentration, and distribution significantly impact the strength and properties of fiber-reinforced composites, with two possible extremes in ______.

<p>orientation</p> Signup and view all the answers

The mechanical properties of a fiber-reinforced composite depend on the fiber's properties and the load transmitted by the ______ phase.

<p>matrix</p> Signup and view all the answers

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