COMPOSITE MATERIALS Flashcards
What is a composite material?
A composite material is a material system consisting of two or more distinct phases whose combination results in properties that differ from those of its constituents.
Identify some of the characteristic properties of composite materials.
Typical properties include (1) high strength-to-weight and stiffness-to-weight ratios; (2) good fatigue properties and toughness; (3) anisotropic properties in many cases; and (4) other properties and features that are difficult or impossible to obtain with metals, ceramics, or polymers alone.
What does the term anisotropic mean?
Anisotropic means that the properties of a material vary depending on the direction in which they are measured.
Name the three basic categories of composite materials.
Metal matrix composites (MMCs), ceramic matrix composites (CMCs), and polymer matrix composites (PMCs).
What are the common forms of the reinforcing phase in composite materials?
The forms are: (1) fibers, (2) particles and flakes, and (3) an infiltrated phase in skeletal structures.
What is a whisker?
A whisker is a thin, hairlike crystal of very high strength.
What are the two forms of sandwich structure among laminar composite structures? Briefly describe each.
The two forms are (1) foamed-core sandwich, in which the core is polymer foam between two solid skins; and (2) honeycomb, in which the core is a honeycomb structure sandwiched between two solid skins.
Give some examples of commercial products which are laminar composite structures.
Examples given in Table 9.2 are automotive tires, honeycomb sandwich structures, fiber reinforced polymer structures such as boat hulls, plywood, printed circuit boards, snow skis made from fiber reinforced polymers, and windshield glass.
What are the three general factors that determine the properties of a composite material?
Three factors are given in the text: (1) the component materials; (2) the geometric shapes of the constituents - the reinforcing phase in particular - and the resulting structure of the material; and (3) the interaction of the phases.
What is the rule of mixtures?
The rule of mixtures applies to certain properties of composite materials; it states that the property value is a weighted average of the property values of the components, the weighting being by proportions of the components in the composite.
What is a cermet?
A cermet is a composite material consisting of a ceramic and a metal. In the text, it is defined as a composite consisting of ceramic grains imbedded in a metallic matrix.
Cemented carbides are what class of composites?
A cemented carbide is a cermet; although the cemented carbide industry does not generally think of cemented carbides as cermets, they fit within the definition.
What are some of the weaknesses of ceramics that might be corrected in fiber-reinforced ceramic matrix composites?
Weaknesses of ceramics include low tensile strength, poor toughness, and susceptibility to thermal cracking.
What is the most common fiber material in fiber-reinforced plastics?
E-glass.
Identify some of the important properties of fiber-reinforced plastic composite materials.
Properties include high strength-to-weight ratio, high modulus-to-weight ratio, low density, good fatigue strength, good corrosion resistance, and low thermal expansion for many FRPs.
