Which of the following materials is used for car tyres as a standard material?
Weldable type plastic(s) include(s):
Weldable plastics are: Polypropylene, Polycarbonate, Acrylic, Nylon, ABS.
The windows of aeroplane are made of
Which one is not a characteristics of plastics?
Plasticizers are added in plastic to
Whiskers are very thin filaments, hair-like single crystals of about 13 mm length and 10-4 cm diameter (approx). These are produced as dislocations of free - crystals and are without any structural defect. Whiskers are far stronger than polycrystals of same materials.
The cermets are example of
A continuous and aligned glass fibre-reinforced composite consists of 40 vol% of glass fibres modulus of elasticity 69 GPa and 60 vol% of a polyester resin that, when-hardened, displays a modulus of 3.4 GPa. What is the modulus of elasticity of this composite in the longitudinal direction?
ECL = Em Vm + Ef Vf = 3.4 x 0.6 + 69 x 0.4
= 2.04 + 27.6 = 30 GPa
A continuous and aligned glass fibre-reinforced composite consists of 40 vol% of glass fibres having a modulus of elasticity 80 GPa and remaining volume of a polyester resin that, when hardened, displays a modulus of 4 GPa. What is the elastic modulus of composite material when the stress is applied perpendicular to the direction of fibre alignment?
The matrix phase of fibrous composites may be
Which of the following is not an example of laminar composite?
When multidirectional stresses are imposed within a single plane, a ligned layers that are fastened together one on top of another at different orientations are frequently utilized. These are called laminar composites. These are generally designed to provide high strength and low cost at a lighter weight.
Wood is a natural polymer composite with principal polymeric molecules being those of cellulose. It is composed of cells resembling long tubes with tapered ends.
Ceramic cutting tools are made of
Which one of the following materials is not a composite?
Consider the following statements regarding composite materials:
1. Material is termed as advanced composite if fibres are directionally oriented and continuous.
2. Reinforced fibres glass products are strong and light weight,
3. Concrete is reinforced with steel bars and the bar becomes matrix.
4. Pearlitic steels are composites.
Q. Which of the above statements are true?
Consider the following statements pertaining to composite materials:
1. The mechanical characteristics of a fibre-reinforced composite depend only on the properties of the fibre.
2. Prestressed concrete should be of a high quality with a low shrinkage and a low creep rate.
3. Whiskers are very thin single crystals that have extremely large length-to-diameter ratio.
Q. Which of the above statements are valid?
The mechanical characteristics of a fiber-reinforced composite depend not only on the properties of the fiber, but also on the degree to which an applied load is transmitted to the fibers by the matrix phase.
Slow and progressive deformation of a material with time under constant stress is called creep.This phenomenon is not exhibited at low temperature by
Select the wrong statement:
Viscoelastic behaviour would be exhibited by
Consider the following statements:
Thermosetting plastics are
1. Formed by addition polymerization
2. Formed by condensation polymerization
3. Softened on heating and hardened on cooling
4. Moulded by heating and cooling
Q. Which of these statements are true?
Teflon is a
Phenol formaldehyde is a
Structure of a polymer is
Polyesters can be defined as the condensation products of
Match List-I (Materia!) with List-II (Typical use) and select the correct answer using the codes given below the isits:
List - I
A. Branched polyethylene
C. Polyvinyl chloride
D. Linear Polyethylene
List - II
2. Textile fibres
3. Films forpackaging
4. Transparent Film
A B C D
(a) 3 2 1 4
(b) 2 3 4 1
(c) 2 3 1 4
(d) 3 2 4 1
Match List-I with List-II and select the correct answer using the codes given below the lists:
C. Foamed poly-urethane
1. Electric switches
3. Thermal insulator
4. Oil seal
A B C D
(a) 4 1 2 3
(b) 1 4 2 3
(c) 4 1 3 2
(d) 1 4 3 2
(i) Neoprenes are used as wire and cable, chemical tank linings, belts, hoses, seals and gaskets. It has excellent heat and weathering resistance and also good oil resistance.
(ii) Bakellte has excellent thermal stability to over 150°C and may be compounded with a large number of resins, fillers.
It is used in motor housing, telephones, auto distributor and electrical fixtures.
(iii) Foamed Polyurethane are commonly used as cushions in auto mobiles and furniture as well as in packaging and thermal insulation.
(iv) Araldite has excellent combination of mechanical properties and corrosion resistance, dimensionally stable, good adhesion, relatively inexpensive and good electrical properties.
The molecular weight of vinyl chloride is 62.5. Thus the molecular weight of a polyvinyl chloride with a degree of polymerization of 20000 is