Materials And Processes - Chapter 5

Question 1

Plastics that soften with increasing temperature and regain rigidity as the temperature is decreased are called:

Answer 1

thermoplastic

Question 2

Plastic materials that cannot be returned to their original state after they have been exposed to higher temperatures during the manufacturing process are referred to as:

Answer 2

thermosetting

Question 3

The greatest variety of plastics comprises:

Answer 3

synthetic materials

Question 4

The most important area of plastic processing is:

Answer 4

matched die molding

Question 5

Compression molding, cold molding, transfer molding, and injection molding are all examples of what type of plastic processing?

Answer 5

Matched die molding

Question 6

_______ materials may be held in the softened condition for prolonged periods of time with little or no chemical change.

Answer 6

Thermoplastic

Question 7

The high pressures required by compression molding, together with the low viscosity of most thermosetting materials, require that the mold halves have fitting clearance on the order of:

Answer 7

0.025 mm (0.001 in.)

Question 8

The spruce and runner system, or “cull,” that is produced during the transfer molding process:

Answer 8

must be removed and cannot be reused

Question 9

The injection molding process for thermosetting plastics is referred to as:

Answer 9

jet, flow, or offset molding

Question 10

A low tooling cost procedure restricted to thermosetting resins used for low production of jewelry, novelty items, laboratory specimens, and similar parts is called:

Answer 10

casting of plastics

Question 11

Thin plastic film is produced either by extruding the plastic through a slit of the appropriate size or by:

Answer 11

the expanded tube method

Question 12

Vacuum bag, expanded bag, and autoclave molding are all methods for developing some pressure on the surface of the molding to permit a low resin-to-filler ratio. These are all variations of which type of reinforced plastic molding technique?

Answer 12

Contact layup

Question 13

The strength of concrete increases with time. Solidity may occur from a few hours to a few days, but what is defined as 100% strength requires _______

Answer 13

28 days

Question 14

Engineered material consisting of one or more reinforcing agents and a matrix binder acting together as a physical unit while retaining their identities describes what type of material?

Answer 14

Composite

Question 15

Tension, compression, torsion, shear, and bending are all examples of:

Answer 15

stress modes

Question 16

The proper performance of an adhesive requires bonding, surface cleanliness, and _______ as a minimum.

Answer 16

intimate contact

Question 17

Synthetic fiber in a random assortment of fixed length, or chopped random length fiber yarns that are bound together on a flat mat describes:

Answer 17

discontinuous fiber

Question 18

Fiber used as reinforcement for very high temperature applications is known as:

Answer 18

ceramic fiber

Question 19

The most common fiber used for composites (90%), because of its high tensile strength and its resistance to heat, fire, moisture, and chemicals is:

Answer 19

glass fiber

Question 20

Fiber used as reinforcement, which exhibits extreme tensile strength, impact resistance, and vibration dampening is known as:

Answer 20

aramid fiber

Question 21

Fiber used as reinforcement, which has very high tensile strength and makes very stiff, lightweight structures and also has very high compressive strength and a negative coefficient of thermal expansion is known as:

Answer 21

carbon fiber

Question 22

Chemically, plastics are all polymers. The smallest unit structure or molecule that identifies the chemical involved is called a(n):

Answer 22

monomer

Question 23

Drawn filaments of which material may have a tensile strength of 345 MPa (50 000 psi), which is actually greater than some low-strength steels?

Answer 23

Nylon

Question 24

The basic steps of primary fabrication of continuous fiber composites are layup and:

Answer 24

curing

Question 25

In a good adhesive bond:

Answer 25

adhesion forces always exceed cohesion forces

Question 26

Damage to a composite structure that occurs without visual indications at the surface is classified as what type of damage?

Answer 26

Low-velocity impact damage

Question 27

In a low-velocity impact, the most critical damage mechanism in composites is:

Answer 27

delamination

Question 28

What kind of damage is created by factors such as temperature, water pressure, corrosion, erosion, and fire?

Answer 28

Environmental

Question 29

Damage assessment comprises three distinct steps: discontinuity detection/location, discontinuity assessment, and:

Answer 29

discontinuity removal assessment

Question 30

Maintenance manuals for composite material repair normally provide limits (for example, damage size, weight, balance, and repair proximity) based on the criticality of specific parts. In cases where no specific instructions are available or cannot be followed, who makes the repair decision?

Answer 30

The responsible engineering authority