Composite Technology - Introduction to Polymeric Composites with Rice Hulls - page 36

be positioned in the pultrusion product, in which extra strength is required. Hot-melt
thermoplastic materials and resin reinforcements may also be used. Parallel orientation
of reinforcements produces a strong composite to the direction of the fibres. Some
operations will allow the use of SMC or wound preforms in combination with other
continuous reinforcements to improve properties in more than one direction. Some
of the products made this way are: gutters; fishing rods; automotive springs; frames;
golf shafts; tennis racquets; vaulting poles; and other profiled shapes.
3.2.11 Cold Stamp Forming
Fibrous glass-reinforced thermoplastics and HIPS in sheet form can be cold-formed
similar to that seen for metal sheet stamping. These products will have long
reinforcements and special additives to improve the strength:mass ratio. During
the forming process, a sheet is pre-heated to ≈198.8 °C and then formed on normal
standard steel stamping presses. It is possible to produce parts with complex designs
and varying wall thicknesses with this method. Production rates will be dependent
upon the equipment used but, in general, on average outputs ≈200 per h can be
achieved. Common products made this way are: motor covers, housings, appliance
bodies, seat backs, outdoor furniture, automotive interior trims and many others.
3.3 General Properties of Composites
The designer of composite products must have a good knowledge of the properties
and behavioural patterns of the individual constituent materials to be used to achieve
the maximum desired properties of the final composite. In the context of polymeric
composites, a sound understanding of polymer properties will help greatly. Hence, one
may make use of the many information sheets on the properties and specifications of
polymers available. In this section, only the relevant properties of polymeric composites
that are important for the practical end applications of these composites are discussed:
• Density
• Compressivestrength
• Impactstrength
• Permeabilityandsorption
• Weathering