Question & Answer

In problem 9.3, what is the predicted value for the modulus of elasticity (a) in the longitudinal direction and (b) the perpendicular to the carbon fibers?

A composite sample of carbon reinforced epoxy has dimensions of 12 in by 12 in by 0.25 in and mass of 1.8 lb. The carbon fibers have a modulus of elasticity of 50(106 ) lb/in2 and a density of 0.069 lb/in3 . The epoxy matrix has modulus of elasticity of 0.61(106 ) lb/in2 and a density of 0.042 lb/in3 . What is the volume fraction of (a) the carbon fibers and (b) the epoxy matrix in the sample? Assume there are no voids in the sample.

For problem 9.1, determine the modulus of elasticity in (a) the longitudinal direction of the glass fibers and (b) the perpendicular direction to the glass fibers.

A fiberglass composite is composed of a matrix of vinyl ester and reinforcing fibers of E-glass. The volume fraction of E-glass is 35%. The remainder is vinyl ester. The density of the vinyl ester is 0.882 g/cm3 , and its modulus of elasticity is 3.60 GPa. The density of E-glass is 2.60 g/cm3 , and its modulus of elasticity is 76.0 GPa. A section of composite 1.00 cm by 50.00 cm by 200.00 cm is fabricated with the E-glass fibers running longitudinal along the 200-cm direction. Assume there

are no voids in the composite. Determine the (a) mass of vinyl ester in the section, (b) mass of Eglass fibers in the section, and (c) the density of the composite

There are 19 correct answers in the following multiple-choice questions (some questions have multiple answers that are correct). To attain a perfect score on the quiz, all correct answers must be given. Each correct answer is worth 1 point. Each omitted answer or wrong answer reduces the score by 1 point, and each additional answer beyond the correct number of answers reduces the score by 1 point. Percentage score on the quiz is based on the total number of correct answers.

9.1 Anisotropic means which one of the following: (a) composite materials with composition consisting of more than two materials, (b) properties are the same in every direction, (c) properties vary depending on the direction in which they are measured, or (d) strength and other properties are a function of curing temperature?

9.2 The reinforcing phase is the matrix within which the secondary phase is imbedded: (a) true or (b) false?

9.3 Which one of the following reinforcing geometries offers the greatest potential for strength and stiffness improvement in the resulting composite material: (a) fibers, (b) flakes, (c) particles, or (d) infiltrated phase?

9.4 Wood is which one of the following composite types: (a) CMC, (b) MMC, or (c) PMC?

9.5 Which of the following materials are used as fibers in fiber-reinforced plastics (four best answers): (a) aluminum oxide, (b) boron, (c) cast iron, (d) E-glass, (e) epoxy, (f) Kevlar 49, (g) polyester, and (h) silicon?

9.6 Which of the following metals are used as the matrix material in fiber-reinforced MMCs (two best answers): (a) aluminum, (b) copper, (c) iron, (d) magnesium, and (e) zinc?

9.7 Which of the following metals are used as the matrix metals in nearly all WC cemented carbides and TiC cermets (two correct answers): (a) aluminum, (b) chromium, (c) cobalt, (d) lead, (e) nickel, (f) tungsten, and (g) tungsten carbide?

9.8 Ceramic matrix composites are designed to overcome which of the following weaknesses of ceramics (two best answers): (a) compressive strength, (b) hardness, (c) hot hardness, (d) modulus of elasticity, (e) tensile strength, and (f) toughness?

9.9 Which one of the following polymer types are most commonly used in polymer matrix composites: (a) elastomers, (b) thermoplastics, or (c) thermosets?

9.10 Which of the following materials are not composites (two correct answers): (a) cemented carbide, (b) phenolic molding compound, (c) plywood, (d) Portland cement, (e) rubber in automobile tires, (f) wood, and (g) 1020 steel?

What is meant by the term interface in the context of composite materials?

Name some of the important applications of FRPs.

Identify some of the important properties of fiber-reinforced plastic composite materials

What is a hybrid composite?

What does the term advanced composites mean?

What is the most common fiber material in fiber-reinforced plastics?

What are some of the weaknesses of ceramics that might be corrected in fiber-reinforced ceramic matrix composites?

Cemented carbides are what class of composites?

What is a cermet?

What is the rule of mixtures?

What are the three general factors that determine the properties of a composite material?

Give some examples of commercial products which are laminar composite structures

What are the two forms of sandwich structure among laminar composite structures? Briefly describe each

What is a whisker?

What are the common forms of the reinforcing phase in composite materials?

Name the three basic categories of composite materials

How are traditional composites distinguished from synthetic composites?

What does the term anisotropic mean?

Identify some of the characteristic properties of composite materials.

What is a composite material?