Module 06 Materials and Hardware 100 Important Sentences for Revision

1. Basic Material Properties

1. Material science studies properties and behavior of engineering materials.
2. All materials are classified as metals, ceramics, polymers, or composites.
3. Metals are good conductors of heat and electricity.
4. Non-metals are poor conductors of heat and electricity.
5. Density is mass per unit volume.
6. Elasticity is the ability of a material to return to its original shape after deformation.
7. Plasticity is the ability to permanently deform without breaking.
8. Ductility allows a material to be drawn into wires.
9. Malleability allows a material to be hammered into thin sheets.
10. Brittleness means a material breaks easily without deformation.

2. Mechanical Properties

11. Tensile strength is the maximum stress before breaking.
12. Compressive strength resists squeezing forces.
13. Shear strength resists sliding forces.
14. Hardness measures resistance to indentation.
15. Toughness is the ability to absorb energy before fracture.
16. Fatigue is failure caused by repeated stress cycles.
17. Creep is slow deformation under constant stress and temperature.
18. Stress is force per unit area.
19. Strain is the deformation caused by stress.
20. Hooke’s Law states stress is proportional to strain within elastic limit.

3. Ferrous and Non-Ferrous Metals

21. Ferrous metals contain iron.
22. Non-ferrous metals do not contain iron.
23. Steel is an alloy of iron and carbon.
24. Stainless steel contains chromium for corrosion resistance.
25. Cast iron is brittle but strong in compression.
26. Aluminum is lightweight and corrosion resistant.
27. Copper is a good conductor of electricity.
28. Brass is an alloy of copper and zinc.
29. Bronze is an alloy of copper and tin.
30. Titanium is strong, light, and resistant to corrosion — used in aircraft.

4. Heat Treatment

31. Heat treatment changes the physical properties of metals.
32. Annealing softens the metal and relieves stress.
33. Normalizing refines grain structure and improves toughness.
34. Hardening increases hardness by rapid cooling.
35. Quenching is the process of rapid cooling in oil or water.
36. Tempering reduces brittleness after hardening.
37. Case hardening hardens only the surface of steel.
38. Solution heat treatment is used for aluminum alloys.
39. Precipitation hardening increases strength by forming fine particles.
40. Age hardening strengthens certain alloys over time.

5. Corrosion and Protection

41. Corrosion is the deterioration of metal by chemical or electrochemical reaction.
42. Oxidation is a common form of corrosion.
43. Galvanic corrosion occurs when two dissimilar metals contact in moisture.
44. Pitting corrosion causes small, deep holes in metal.
45. Intergranular corrosion occurs along grain boundaries.
46. Filiform corrosion appears as thread-like lines under paint.
47. Stress corrosion cracking occurs under tensile stress and corrosive environment.
48. Erosion corrosion is caused by high-speed fluid flow.
49. Fretting corrosion occurs due to vibration and movement.
50. Protective coatings and paints prevent corrosion.

6. Composite Materials

51. Composite materials are made of two or more different materials.
52. Fiber-reinforced plastics are commonly used in aircraft.
53. Matrix binds the reinforcement together.
54. Reinforcement provides strength and stiffness.
55. Glass fibre is cheap but less strong.
56. Carbon fibre is lightweight and very strong.
57. Kevlar fibre is strong and resistant to impact.
58. Honeycomb structures provide high strength with low weight.
59. Sandwich panels consist of skins and core.
60. Composites are resistant to corrosion and fatigue.

7. Plastics and Rubber

61. Thermoplastics soften when heated and harden when cooled.
62. Thermosetting plastics harden permanently when heated.
63. Nylon, polyethylene, and PVC are thermoplastics.
64. Epoxy and phenolic resins are thermosetting plastics.
65. Rubber is an elastic material used for seals and gaskets.
66. Natural rubber is made from latex of trees.
67. Synthetic rubber is made from petroleum products.
68. O-rings provide tight seals in hydraulic and fuel systems.
69. Plastic components are lightweight but can deform with heat.
70. Plasticizers improve flexibility of plastics.

8. Aircraft Hardware

71. Aircraft hardware includes bolts, nuts, screws, rivets, and washers.
72. AN and MS standards are used for aircraft fasteners.
73. Bolts are used where high strength is required.
74. Screws are used for light loads and soft materials.
75. Self-locking nuts prevent loosening from vibration.
76. Cotter pins secure castle nuts.
77. Washers distribute load and protect surfaces.
78. Rivets are permanent fasteners for joining metal sheets.
79. Solid rivets require access to both sides of the joint.
80. Blind rivets are used where only one side is accessible.

9. Bearings, Pipes, and Control Cables

81. Bearings reduce friction between moving parts.
82. Ball bearings use spherical balls between races.
83. Roller bearings use cylindrical rollers for higher load capacity.
84. Plain bearings rely on lubrication between surfaces.
85. Bushings are sleeve-type plain bearings.
86. Flexible hoses are used for fluid systems.
87. Rigid pipes are made from aluminium or stainless steel.
88. Pipe fittings include flared, flareless, and beaded types.
89. Safety wiring prevents loosening of critical fittings.
90. Aircraft control cables are made of stainless steel.

10. Inspection, Testing, and Safety

91. Visual inspection detects surface defects.
92. Dye penetrant testing reveals surface cracks.
93. Magnetic particle testing detects surface cracks in ferrous metals.
94. Eddy current testing detects cracks without removing paint.
95. Ultrasonic testing detects internal flaws using sound waves.
96. Radiographic testing uses X-rays for internal inspection.
97. Hardness testing determines resistance to indentation.
98. Impact testing measures material toughness.
99. Always wear PPE during material handling and testing.
100. Proper storage prevents corrosion and contamination of materials.