COMPOSITES
SECTION TITLE
material itself. More practically, carbon fibres are not transparent, so laminate defects may not be visually detectable.
GLASS FIBRES When high strength and stiffness are less critical, glass fibres offer a cost-effective and less energy-intensive alternative to carbon. Often selected for marine, renewable energy and industrial applications, they exhibit good specific strength, fatigue performance and stiffness. In structures that must interface with steel fabrications, their similar thermal expansion characteristics also help avoid thermally induced stresses. Te transparency of glass fibres can be beneficial as it simplifies the detection of laminate flaws. At 2500-2600 kg/m3
, their density is
higher than that of carbon, but still only a third of that of steel. It is important to note that the strength of glass fibres can be reduced by exposure to certain environments, for example marine, although this effect can be mitigated by careful matrix selection. Some applications, such as tidal energy blades, benefit from the use of both carbon and glass fibres: Te widespread use of glass keeps overall cost down whilst the careful targeting of carbon reinforcement permits a slimmer structure than would otherwise be possible.
NATURAL FIBRES Of growing interest in recent years are natural fibres, which offer lower impact manufacturing. Te most commonly used
Comparison of composite fibre types
natural fibre is flax, however hemp and jute are also options. Natural fibres offer light weight – flax fibre density is approximately 1450kg/m3
– but their strength is lower than other fibre types. Furthermore, the
attraction of biodegradability confers the disadvantage of limited environmental resistance
ARAMID FIBRES Aramid fibres, such as Kevlar, are employed in niche applications. Teir main selling point is a combination of high strength and strain to failure, and low density. Ideal for ballistics protection, they absorb very high levels of energy before rupture. At 1440kg/ m3
, the density of aramid fibres is similar to that of flax.
Composite materials aren’t the answer to
every engineering problem, but with a wide range of fibres to choose from, it is no surprise that they are becoming ever more commonplace in the modern world. How could your next project benefit from composites?
Matt Dawson is the Director and Chief Engineer at Orthotropic Engineering. Find out more information at
www.orthotropic.co.uk
www.engineerlive.com 39
O2 tidal turbine with composite blades – Orbital Marine Power Ltd
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52
