Composite Materials Material Science and Engineering

Material Science And Engineering introduction to composites.

1. EG 244 Material Science I Composite materials Enzoh Langi (PhD) [email protected]/[email protected] Office: HOD Mechanical Department – School of Engineering Welcome!

2. Composite Materials Introduction What is a composite material?? Can you think of any examples of where composites are used??

3. A composite is a material with two or more distinct constituents or phases that have different physical or chemical properties . They are composed of two or more materials at a microscopic scale and have chemically distinct phases. They are heterogeneous at microscopic scale but statically homogeneous at macroscopic scale. Constituent materials have significantly different properties Composite Materials Introduction

4. These constituents are constructed into a complex structure at different levels (scales). A class of materials that have improved performance compared with that of their constituent materials. What then are the differences between composite materials and alloys??? Composite Materials Introduction

5. Composite Materials Introduction

6. In the 1950s and 1960s, developments in the aerospace and defence industries triggered the design of composite materials. Today, they are still target structural materials, promoted by the advancements in industrial technology. FOCUS!!! WHY do we combine two or more components with different physical and chemical properties? HOW do we combine these components together? What kind of INTERFACE will be formed after the combination of the components? What is the PERFORMANCE of the resulting composites? Finally, how do we measure the composite structures and their performance ? Composite Materials Introduction

7. Why composite materials? Enhanced desired properties! What are these desired properties? Strength Stiffness Toughness Corrosion resistance Wear resistance Reduced weight Fatigue life Thermal/Electrical insulation and conductivity Acoustic insulation Tailorable properties Composite Materials Introduction

8. Reasons for using Composites

9. Reasons for using Composites

10. Reasons for using Composites

11. Reasons for using Composites

12. Composition of composites

13. Composition of composites A composite matrix may be a  polymer ,  ceramic , metal  or  carbon .  Polymer matrices are the most widely used for composites in commercial and high-performance aerospace applications

14. Matrix: Usually a ductile, or tough, material Low density Strength usually = 1/10 (or less) than that of fibres Serves to hold the fibre (filler) in a favourable orientation. Transfer stress to other phases Protect phases from environment Fibres and matrix

15. Fibres and matrix Fibre/Reinforcements Stronger and stiffer than matrix Low densities High load bearing

16. Fibre Reinforcements Used because they are lightweight, stiff, and strong. They are stronger than the bulk material from which they are made This is because of two reasons: The preferential orientation of molecules along the fibre direction The reduced number & sizes of defects in them, as opposed to the bulk material. Whereas the tensile strength of bulk E-glass is low ( 1.5 GPa ), fibres made from the same material reaches 3.5 GPa .

17. Fibre Reinforcements Used as continuous reinforcements in unidirectional composites by aligning them in a thin plate or shell, called lamina or ply . Unidirectional laminas have maximum stiffness and strength along the fibre direction And minimum in a direction perpendicular or transverse to the fibres. When the same properties are desired in every direction random orientation of fibres maybe considered.

18. Fibre Reinforcements - Types A variety of fibres are used as reinforcements in structural applications. Choice involves trade-offs among mechanical , environmental properties , and cost. Fibers can be classified by their; Length – short, long, or continuous fibres; Strength and/or stiffness – low (LM), medium (MM), high (HM) and ultrahigh modulus UHM. Chemical composition - organic and inorganic. The most common inorganic fibres used in composites are glass, carbon, boron, ceramic, mineral, and metallic. The organic fibres used in composites are polymeric fibres.

19. Fibre Reinforcements - Types

20. Fibre Reinforcements - Types Main types of fibre reinforcement used in composite structures, How they are made, and Some of the advantages and disadvantages are considered. Focus will be on: Glass fibres Silica & quartz fibres Carbon fibres Aramid fibres And other types like boron, polyester and natural fibres .

21. Fiber Reinforcements - Types Fibres can be classified by; Their length – short, long, or continuous fibres;

22. Fibre Reinforcements – Glass Fibres Glass fibers are processed from bulk glass An amorphous substance made from a blend of sand, limestone, and other oxidic compounds. Hence, the main chemical constituent (46–75%) is silica (SiO 2 ). Typical properties include hardness , corrosion resistance , and inertness . Furthermore, they are flexible , lightweight , and inexpensive

23. Fibre Reinforcements – Glass Fibres By controlling the chemical composition and the manufacturing process, a wide variety of glass fibre types are obtained. Glass fibres are the most common type of fibres used in low-cost industrial applications. They have similar stiffness but different strength and resistance to environmental degradation. E-glass fibres (E for electrical) for high tensile strength and good chemical resistance is required. Hence, it is a preferred structural reinforcement Due to the combination of mechanical performance, corrosion resistance, and low cost

24. Fibre Reinforcements – Glass Fibres Glass fibre mechanical behaviour is known to be influenced by environmental conditions At elevated temperature, tensile strength tends to decrease

25. Fibre Reinforcements – Silica and Quartz Fibres These two fibre types are distinguished from classical glass fibres by their high concentration of silica (SiO 2 ). Concentrations range from 96–98% for silica fibres, and 99.95–99.97% for quartz fibres These fibres cost up to 25–50% more than glass fibres and have enhanced physical and mechanical properties. They have comparable or better stiffness and strength than glass fibres, and thermal stability than glass fibres They have long-term working temperatures of up to 900ºC for silica and up to 1050ºC for quartz fibres.

26. Fibre Reinforcements – Silica and Quartz Fibres Good thermal and electrical insulation properties. Very good stability under different chemicals, Virtually insensitive to humidity. Hence they are widely applied in high temperatures, and highly corrosive environments They tend to have better radio-frequency transparency, hence used in antenna applications.

27. Fibre Reinforcements – Carbon Fibres Also called graphite fibres, They are lightweight and strong fibres with excellent chemical resistance. They are widely used in the aerospace industry. Mechanical properties are determined by the atomic configuration of carbon chains and their connections, These are similar to the graphite crystal structures. Strength is controlled by orienting the carbon atomic structures with their strongest atomic connections along the carbon fibre direction.

28. Composite Materials Matrix –

29. Composite Materials Matrix –

30. Composite Materials Matrix –

31. Processing and Composites Questions A composite material is a combination of a reinforcing element and ___________. How are advanced composites distinguished from reinforced plastics?_________ The fibers in advanced composites are usually made from what? ____________ What two functions does the matrix of a composite serve? ________________ Under what conditions should graphite fibers OR carbon fibers be used? _______ 32

32. Carbon fibres

33. Carbon fibres - Applications Use of the barrel sections removes 50,000 rivets Boeing 787 (50% composite, 15% aluminium, 12% titanium)

34. Carbon fibres - Applications Advantages: Fuel efficiency Lower maintenance costs Eliminate metal fatigue and corrosion problems Less noise – 60% smaller noise footprint Boeing 787 (50% composite, 15% aluminium, 12% titanium)

35. Carbon fibres - Applications Sports equipment

36. Carbon fibres - Applications Musical instruments

37. Wing leading edge structures– protect against foreign object impact Composite sandwich structures – SLM built lattice cores Reduced damage area, increased energy absorption – although higher weight! Carbon fibres - Applications

38. Structure of Graphite Basal planes (Hexagonal layers) Strong covalent bonds Weak van der Waals forces

39. Carbon fibre structure Basal plane Ribbon structures Carbon are oriented parallel to the fiber axis Carbon fibers achieve their exceptional strength due to the interlocking and folding  http://web.mit.edu/3.082/www/team2_f01/chemistry.html

40. Comparison of properties of CF with other materials Low density + High strength = V. high specific strength

41. Carbon fibres are produced by the controlled oxidation , carbonisation and graphitisation of carbon-rich organic precursors which are already in fibre form. The most common precursor is polyacrylonitrile (PAN), because it gives the best carbon fibre properties. Fibres can also be made from pitch or cellulose. PAN How are carbon fibres made?

42. Manufacturing process: PAN fibres are stretched by between 500 and 1300% to improve molecular alignment 2) They are then stabilised (oxidised) in air at 300 ° C. 3 ) They are then carbonised at 1500°C to improve crystallinity. Nitrogen is released and fibres are now about 90% carbon. 4) Finally, they are graphitised by heating and stretching at temperatures up to 3000°C. How are carbon fibres made?

43. The fibres have a surface treatment applied to improve matrix bonding and a chemical size that serves to protect it during handling. Carbon fibre - 5-10 microns Carbon fibres

44. Advantages: High strength and high modulus, creep and fatigue resistance, good energy absorption (as used in structural panels in F1 cars). Disadvantages: cost, poor impact resistance, electrical conductor Carbon fibres

45. Comparison of fibre properties

46. Other types of fibre

47. Polyester fibres A low-density fibre with good impact resistance but low modulus . Its lack of stiffness usually precludes it from inclusion in a composite component, but it is useful where low weight, high impact or abrasion resistance, and low cost is required. It is mainly used as a surfacing material, as it can be very smooth, keeps weight down and works well with most resin types.

48. Polyethylene fibres In random orientation, ultra-high molecular weight polyethylene (UHMWPE) molecules give very low mechanical properties. However, if dissolved and drawn from solution into a filament by spinning, the molecules become disentangled and aligned in the direction of the filament.

49. The manufacturing process involves: Dissolving the polymer in a solvent and heating. The viscous liquid is then spun and quenched in a cooling bath. Following this, the fibres are heated and stretched up to 100 times their original length – fibre orientation. The solvent is then removed by heating. The drawing procedure orientates the molecules, giving a very high tensile strength to the resulting fibre. Polyethylene fibres

50. Quartz fibres A very high silica version of glass with much higher mechanical properties and excellent resistance to high temperatures. They have lower density, higher strength and higher modulus than E-glass, and about twice the elongation-to-break, making them a good choice where durability is a priority. However, the manufacturing process and low volume production lead to a very high price (14micron - £74/kg, 9micron - £120/kg).

51. Quartz fibres (CTE =coefficient thermal expansion) Quartz fibres also have a near-zero CTE ; they can maintain their performance properties under continuous exposure to temperatures as high as 1050°C and up to 1250°C for short time periods. Quartz fibres possess significantly better electromagnetic properties than glass, a plus when fabricating parts such as aircraft radomes .

52. Boron fibres Here, carbon or metal fibres are coated with a layer of boron using a vapour deposition technique. Boron fibres are five times as strong and twice as stiff as steel. Boron provides strength, stiffness and light weight, and possesses excellent compressive properties and buckling resistance.

53. Boron fibres The extremely high cost of this fibre restricts it use to high temperature aerospace applications and in specialised sporting equipment. Applications: High beam stiffness High torsional stiffness Low density High strength Golf clubs, tennis racquets, skis, surfboards, fishing rods .

54. Ceramic fibres Ceramic fibres, usually in the form of very short ‘whiskers’ are mainly used in areas requiring high temperature resistance. They are more frequently associated with non-polymer matrices such as metal alloys (MMC’s).

55. Ceramic fibres Ceramic fibres offer high to very high temperature resistance but low impact resistance and relatively poor room-temperature properties. Typically much more expensive than other fibres, ceramic, like quartz, is the fibre of choice when its advantages justify the extra cost. Ceramic composites also are being considered for use in certain high-heat aircraft engine applications.

56. Natural fibres At the other end of the scale it is possible to use fibrous plant materials such as abaca, coconut, flax, hemp, jute and sisal as reinforcements in ‘low-tech’ applications. In these applications, the fibres’ low specific gravity (typically 0.5-0.6) mean that fairly high specific strengths can be achieved.

57. Natural fibres Natural fibres are enjoying increased use because of their “green” attributes (less energy to produce), light weight, recyclability, good insulation properties and carbon dioxide neutrality (when burned, natural fibres give off no more carbon dioxide than was consumed to grow the source plant).

58. Natural fibres Natural fibre-reinforced thermosets and thermoplastics are most often found in door panels, package trays, seat backs and trunk liners in cars and trucks. European fabricators hold the lead in use of these materials, in part because regulations now require their automobile components to be recyclable .

59. There are advantages in combining different types of fibres in one composite to produce a hybrid. Fibre hybrids capitalise on the best properties of more than one fibre type and can reduce raw material costs. The term hybrid refers to a fabric that has more than one type of structural fibre in its construction. Hybrid composites

60. Hybrid composites that combine carbon/aramid or carbon/glass fibres have been used successfully in ribbed aircraft engine thrust reversers, telescope mirrors, drive shafts for ground transportation, and in the infrastructure arena, column-wrapping systems that reinforce concrete structural members. Hybrid composites