Tutorial 1

(1) Write down three examples of applications of composite materials from our daily life. Describe the matrix and second phase. Indicate the advantages of these composites.

(1) Specific product: the Lotus bicycle _ The Lotus bicycle is made from carbon-fibre reinforced polymer. _ Carbon fibre is used to create a monocoque shell structure to replace traditional aluminum alloy frame. _ Superb strength-to-weight ratio of CFRP meant that a very light, aerodynamic chassis could be made. In contrast, a traditional aluminum frame was heavier and the tube construction created drag or wind resistance. _ The CFRP chassis is made by lay-up moulding techniques so it was possible to make the bicycle fit the body and the riding position of Boardman as closely as possible. It is relatively easy to add or remove parts from the master moulds to make dimensional or design changes as these are simply made from wood. It is much more difficult to shape aluminum to accommodate design changes.

(2) TAPE Polymer and Fe3O4. For recording.

(3) Tooth

hydroxyapatite and collagen

(2) Comparing advanced materials (for example, composites) to traditional materials (for example, metals) mention two properties that make composites more attractive than metals, and one property that makes composites less attractive than metals.

(a) Lighter & stronger. Chemical stability (b) expensive

(3) Four rods with the same geometry, shown below, are made of four different composite materials, A, B, C, D. For each rod, the load, P, is increased until the rod breaks. The load, P, and deflection, δ, are plotted below for each rod. For a particular application, if high strength is the most important design criterion, which material should be selected? (b)

a) Material A b) Material B c) Material C d) Material D e) Unable to determine using the given information.

(4) Comparing carbon-fibre reinforced plastic with glass reinforced plastic.

Answer: (a) Carbon-fibre reinforced plastic has excellent tensile strength and can be several times stronger than standard glass reinforced plastic. ( b ) Carbon-fibre reinforced plastic is extremely lightweight. Its strength allows products to be made with less material and often in thinner section than alternative materials such as GRP and aluminium. This would also allow for the manufacture of longer fishing rods whilst still having them light enough to hold and use. ( c ) Carbon-fibre reinforced plastic can be manufactured to have good elastic properties, allowing the fishing rod to flex to a greater extent than GRP. (d) Chemical stability.

Tutorial 2: (1) Use notes and diagrams to show how a product, such as a

boat or vehicle body panel, is manufactured using glass-reinforced plastic (GRP).

(1) A mould of the panel is made first. The mould is coated with a releasing agent (often a wax-like product), which will help the GRP panel to be removed from the mould later. Glass-fibre matting is cut to size and laid over the mould. Polyester resin and catalyst are mixed and applied with brushes to the glass-fibre matting. This is allowed to set. Further layers of glass-fibre matting and resin are applied to the mould in the same way. After setting, high spots and imperfections will be sanded out. A ‘gelcoat’ containing a colour pigment is added to create a hard, waterproof gloss finish to the panel.

(2) Consider a carbon-matrix composite containing continuous carbon fibers :

(a) What are the two main attractive properties of a carbon-matrix composite?

(b) Carbon-matrix composites suffer from poor oxidation resistance. Why?

Answer: (a) The specific strength (strength/density), specific modulus (modulus/density) and specific thermal conductivity (thermal conductivity/density) of carbon-carbon composites are the highest among composites. Furthermore, the coefficient of thermal expansion is near zero. (b) The predominant reaction that occurs in air is C + O2 = CO2. This reaction is associated with a very large negative value of Gibbs free energy charge. So it proceeds with a big driving force even at very low O2 partial pressure. The oxidation of carbon-carbon composites preferentially attacks the fiber-matrix interfaces and weakens the fiber bundles. The unoxidized material fails catastrophically by delamination cracking between plies and at bundle-bundle interfaces within plies. As oxidation progress, failure becomes a multistep process with less delamination cracking and more cross-bundle cracking.

(3) Why are metal-matrix composites not widely used?

Answer: metal composites have high fabrication cost and the limited service experience

(4) What is skin effect? Answer: The process of extrusion through a spinneret results in some chain orientation in the filament. Generally, the molecules in the surface region undergo more orientation than the ones in the interior because the edges of the spinneret hole affect the near-surface molecules more.

(5) The use of fibers as high-performance engineering materials is based on three important characteristics. What are they?

Answer: (1) Size effect: The smaller the size, the lower the probability of having imperfections in the material; (2) A high aspect ratio (length/diameter, l/d), which allows a very large fraction of the applied load to be transferred via the matrix to the stiff and strong fiber; (3) A very high degree of flexibility, which is really a characteristic of a material that has a high modulus and a small diameter. This flexibility permits use of a variety of techniques for making composites with these fibers.

Tutorial 6 (1) A sheet of paper is about 100 000 nm thick, a single gold atom will be about …………. In diameter: (a) 80 000 nm; (b) 2 to 5 µm (c) 0.14 nm (d) 5 mm Answer: (c) 2. Adding nanoparticles to plastics can make them: (a) Stronger, lighter and more durable (b) Stronger, heavier and more durable (c) Weaker, heavier and more durable (d) Weaker, lighter and more durable Answer: (a) 3. In future, nanotechnology could help your clothes respond to …… (a) Medical emergencies (b) One’s life span (c) Weather (d) Fire emergencies Answer: (c) 4. Nano-devices could be used to perform …………. inside the human body: (a) Metabolism process (b) Operations (c) Clean dirt (d) Transport nutrients Answer: (b) 5. When bioplastics are mixed with …………….. particles, the resulting nanocomposites exhibit improved barrier properties compared with the pure bioplastic. (a) Nano diamond (b) Cellulose (c) Nanoclay (d) Nano-oxides Answer: (c) 6. Nanotech coatings can help to reduce …………… of ships (a) Sinking (b) Corrosion (c) Deformation (d) De-colorization. Answer: (b)

9. A large number of healthy substances found in food are poorly absorbed by human body as a result ………………. And ………………… provide a means for improving the bioavailability.

(a) Thin films and coatings (b) Nano-emulsions and nanomicells (c) Biodegradible and substainability (d) Nanofibres and nanocomposites

Answer: (b) 10. ……… is a nano-material permeated with killing agents, growth inhibitors or antibiotics.

(a) Antimicrobial nanocomposite (b) Biopolymer nanocomposite (c) Nanofibre (d) Nanoemulsioner

(a) 11. ………….. is a nano-material used for galvanic coatings, polishing pastes, lubricating oils, coolants, filler in polymer composites and greases (a)CNT (b) Oxide nanoparticle (c) Nano diamond (d) Dendrimer Answer: d 12 What are the barriers to commercialize nano-filtration? (a) Problems with membrane fouling (b) Concerns on possible toxic intermediates (c) Lack of experience with the technology (d) High production costs Answer: (a) 13. What is nanocomposites? Why are layered composites good candidates for packaging? Answer: Nanocomposites are a broad range of materials consisting of two or more components, with at least one component having dimensions in the nm regime (i.e. between 1 and 100 nm): (a) Multi-constituent materials; (b) Superior overall properties compared to constituent properties e.g. optical clarity, strength, stiffness, permeability; (c) Ability to tailor properties.

Constituents have at least one dimension in the nanometer scale. Nanoparticles (Three nano-scale dimensions) Nanofibers (Two nano-scale dimensions) Nanoclays (One nano-scale dimensions)

The silicate blocks are arranged alternately. Imagine a drop of water trying to get through the PLS barrier compared to a conventional filled polymer. The water drop would face more barrier going through the PLS nanocomposites because of the layered silicates arrangement.

Tutorial 7 (1) What are the advantages of nanocomposites? List three different ways to prepare nanocomposites?

The advantages of nanocomposites are: (1) Very high surface area to volume ratios in nanostructures. (2) Apart from the properties of the individual components in a nanocomposite, the

interfaces play an important role in enhancing or limiting overall properties of system.

(3) Interaction of phases at interface is very helpful. (4) Most nano-particles do not scatter light significantly. (5) CNTs and other nano-particles are often essentially defect-free. Three different ways to prepare nanocomposites: (1) Gas Phase Synthesis; (2) Chemical Vapor Condensation; (3) Combustion Flame Synthesis; (4) Liquid Phase Synthesis. 2. Write down one example of a hetero-junction organic solar cell made with composite structures. Explain why this kind of arrangement can enhance the efficiency of solar cells. Answer: PCBM/P3HT heterojunction solar cell. In this type of solar cell, PCBM is an acceptor and P3HT is a donor. When the light shine on this solar cell, P3HT will absorb the phonons and the excited electron will transfer to P3BM. The electrons’ transfer rate from P3HT to PCBM is much faster than electrons coming back from PCBM to P3HT for recombination.

3. What are the benefits of solar electricity?

4. What is biocomposites? What are the advantages of biocomposites comparing to traditional composites?

Answer: A biocomposite made with at least one part, matrix or fiber, that is bio-based.

Application (1) environment -friendly biodegradable composites (2) biomedical composites for drug/gene delivery, tissue engineering applications and cosmetic orthodontics. e.g. in creating scaffolds in bone tissue engineering. Environment advantages: 1. Renewable raw materials 2. Biodegradable 3. Reduced fossil fuel and resource consumption 4. Lower green house emission 5. Lower overall emission and environmental impacts Properties advantages: 1. Low density 2. High mechanical properties