Processing of PMCs

1. Processing of PMCs • Varies from simple intensive methods to automated methods • The methods of production will depend on factors such as cost, shape of components, number of components and required performance

2. 1. Hand methods • Hand lay-up • Mould is treated with a release agent-to prevent sticking • Gel coat layers are placed on the mold- to give decorative and protective surface • Put the reinforcement (woven rovings or chopped strand mat) • The thermosetting resin is mixed with a curing agent, and applied with brush or roller on the reinforcement • Curing at room temperature

3. Concept of hand lay-up process

4. What are the Advantages and Disadvantages of Hand lay-up methods?

5. 2) Spray-up • Variation of hand lay-up • Mould is treated with a release agent-to prevent sticking • Gel coat layers are placed on the mold- to give decorative and protective surface • The gun sprays the mixture of chopped fiber, resin & catalyst on to a mould • Rolled out to remove entrapped air & give a smooth surface • Poor roll out can induce structural weakness by leaving air bubbles, dislocation of fibers and poor wet out

6. Concept of spray-up process

7. 2. Moulding Methods • Matched-die moulding (Acuan Terpadan) -The composite material is pressed between heated matched dies -Pressure required depends on the flow characteristics of the feed materials - The feed materials flows into the contours of the mould and cures at high temp.

8. Matched die-moulding

9. 2 forms of feed materials; • Sheet moulding compound (SMC) Sheet of resin-fiber blend which contains additives (curing agent, release agent & pigments). Clean to be used & give good consistency in properties b) Dough moulding compound (DMC) Blends (in dough forms) of all the necessary constituents (but only short fibers are used)

10. 2. Moulding Methods b) Forming methods by employing gas pressure (Kaedah Tekanan Gas) • 3 methods • Vacuum forming/vacuum bagging (Beg vakum) • Autoclave moulding (Acuan autoclave) • Pressure bagging (Beg tekanan)

11. Vacuum Bagging -1 die is required for this process - Pressure is obtained atmospheric 1. Used preimpregnated reinforcement/ wet lay- up materials 2. Flexible sheet is sealed to the mould 3. Vacuum until air is removed Bleeder/Breather ply is used to trap air.

12. Autoclave, tube structure and • Pressures are supplied in it • - Mould is placed in autoclave • Supply gas (N2), and forced the bag into the mould • Able to produce high density, product for critical applications such as in the aerospace industry • Autoclave Moulding

13. Pressure Bagging • A flexible bag is placed over • the lay-up on the mould • - Atmospheric pressure is used for shaping • - Compressed air forces the lay-up into the mould

14. c) Low pressure, closed mould system • This method consists of placing the reinforcement in a closed mould, then insert the matrix materials into the mould • Example in Resin Transfer Molding (RTM), the low viscosity resin is injected into the closed mouldusing a low pressure, and cured

15. Resin Transfer Molding (RTM) • Is commonly used in the aerospace and automotive industry. • The process consists of mixing resin with a hardener (or initiator) and injecting the combination into a mold which contains dry fibers. • The mix of resin & hardener is then injected at a low pressure of 5 psi (34.5 kPa) into a mold. • The resulting part is cured at room temperature for several hours. Advantages • Low pressure 5 psi (34.5 kPa) • Fiber loadings are typically around 50-60% (Volume) • Preform architecture can be very complicated

16. Typical RTM Process

17. Process diagram of the automotive industry Hand lay-up – used For complex and large Component in small quantity but the process is slow Match die moulding- expensive but component can be produced rapidly RTM- small runs, simmple components, and longer run for more complex components

18. 3. Pultrusion/Pultrusi • Used to manufacture components with continuous lengths and constants cross-sectional shape (rod, tubes, beam, etc) • Continuous process, easily automated (production rates are high, hence it is vey cost effective), variety of shapes are possible • Starting materials can be in the forms of Prepreg or fiber + resin

19. Schematic Diagram of pultrusion process

20. Methods; • Continuous rovings of the reinforcement are impregnated with the resins (passing through a bath of resin) • Then pulled through the heated die (compact & give shape to the composites) • Curing takes place in the heated die & Oven • Puller used to pull the whole system with certain speed (Pultrusion- pulling action)

21. QUIZ-Soalan 2004/2005 • Bincangkan salah satu teknik penghasilan komposit polimer yg menggunakan prapreg sebagai bahan pemula (teknik kering). Perbincangan harus meliputi gambarajah skematik teknik yg dipilih, bagaimana teknik ini beroperasi, kebaikan teknik kering ini jika dibandingkan dengan teknik basah dan produk yang dihasilkan daripada teknik ini.

22. 4. Filament Winding/Pelilitan Filamen • Process to produce a hollow (usually cylindrical) shape • End products; pressure vessel, storage tanks, and aerospace parts such as helicopter blades. • Wet winding (fiber + resin) & dry winding (prepreg)

23. Schematic diagram of filament winding process Helical Circumferential Polar

25. Methods; • The fibers are passed through the resin bath • Then continuously wound onto the mandrel • After number of layers, curing is carried out in an oven or room temperature. • Mandrel is removed

26. Composite Manufacturing & Complexity

27. Some Commercial PMCs • Fiber reinforced epoxy • Glass fibers are common reinforcement for PMCs • Glass fiber reinforces polyesters (GRPs) are popular in the market, glass fiber reinforced epoxies (GREs) are the second • GREs- good strength & stiffness, strong bonding of glass fibers to epoxy

28. GREs are generally employed in low volume & high technology applications • Coupling agents are used to improved wetting and bonding; silanes • Glass fibers in composites can be degraded by water, results in loss of strength • Water reaches the fibers via defects or by diffusion in matrix, then attack the interface

29. Effect of different types of Coupling Agents on the strength of epoxy laminates as a Function of the Time exposed to Boiling Water

30. The effect of a silane coupling agent on interfacial behavior in the presence of water Hydrolysis of the covalent M-O bond b) Shear displacement at the polymer-glass interface

31. Some Commercial PMCs 2) PEEK matrix composites -PEEK – thermoplastic (TP) (advantages of TP???) • PEEK is a relatively costly TP, with good mechanical properties • Used in high performance applications, i.e. carbon fiber reinforced PEEK is a competitor for carbon reinforced epoxy, Al-Cu & Al-Li in the aircraft industry

32. Some Commercial PMCs 3) Rubber Matrix Composites • Reinforced rubber used in conveyer belt, tyres, fire-resistant cable sheathing, etc. • Common type of reinforcement in rubber is Carbon Black (increase stiffness, strength & abrasion resistance). Carbon can absorb most of UV from natural light, hence decrease degredation of rubber

33. Another example of particulate reinforcement is Aluminium tri-hydroxide, which is flame retardant. Can be incorporated up to 70% into the rubber insulation of heavy duty electrical cable. • Hybrid carbon black and continuous reinforcement (steel wire) are used in tyre applications