Part 7. Glass

1. Part 7. Glass • Glazing • Glass fibres

2. Glass for Glazing • Raw Materials • Manufacture • Cutting • Toughening and annealing • Properties • Strength • Durability • Insulation • Solar Heat Gain

3. Three basic types of glass are manufactured: • Plain flat glassMost plain glass used in the UK is now float glass. In this process liquid glass is cooled to give a viscosity sufficiently high for forming and it is then drawn across the surface of molten tin. This method may be used to produce very flat glass in large quantities. • Textured, patterned and wired glassThe rolled glass process is used for the manufacture these types. The glass is drawn in a horizontal ribbon on rollers. If flat glass is required from this process it must be ground. • Laminated glass This is made with two or more sheets of glass which are bonded together with layers of plastic between them

4. Glass for Glazing • Raw Materials • Manufacture • Cutting • Toughening and annealing • Properties • Strength • Durability • Insulation • Solar Heat Gain

5. Toughened Glass Compression Tension Compression Cooling jets

6. The properties of toughened glass • It is stronger in bending than plain glass because bending stresses the outer layers in tension and these are initially in compression. • For the same level of safety it is cheaper and lighter than laminated glass. • If the material is broken the stress distribution becomes unbalanced and it shatters into small and relatively harmless fragments. • It cannot be cut so it must be ordered to size. This has the advantage, however, that the stamp which is put on every sheet will always be there for checking. (note that laminated glass can be cut). • There are restriction on dimensions of holes near the edge of a sheet.

7. Glass for Glazing • Raw Materials • Manufacture • Cutting • Toughening and annealing • Properties • Strength • Durability • Insulation • Solar Heat Gain

8. Transmission and reflection

9. Solar transmission and reflection

10. Methods of reducing solar heat gain: • Tinted glass. This absorbs heat and re-emits some of it outwards. Care should be taken that the sheet of glass heats uniformly, if the perimeter remains cool it may fail in tension. There are special glasses with low thermal expansion but they must be very clearly labelled so that if they are broken the replacement has the same properties. • Partially reflecting glass. This has a thin film on the inner surface which may be added during manufacture or can even be put on in-situ in older buildings. Note that no glass gives one way vision under all circumstances, they depend on the lighting on the "viewing" side being less intense than the other side.

11. Solar glass

12. Part 7. Glass • Glazing • Glass fibres

13. Glass fibre reinforcement: The original grades were: • E-glass electrical • C-glass chemical resistant • S-glass high strength • M-glass low modulus E-glass is used for most polymer reinforcement applications.

14. The glass come in four different forms • Loose chopped strand (e.g. for fibre reinforced concrete) • Chopped strand mat (cheap fabric) • Rovings (yarn) • Woven roving (expensive fabric)

15. Fabric Weave Styles

16. Fabric Weave Styles 2 x 2 Twill 4 Harness Satin

17. Stitched bi-axial (+/-45°)

18. Basic Properties of Engineering Materials

19. Comparative Cost

20. Rival Materials to Glass Fibre