Carbon fibre / epoxy composite components can be considerably less than half the weight compared to using steel or other metals. Particularly in the case were the load path is along one direction and therefore the fibres can be aligned in the direction of the load path. Composites can be moulded into complex shapes and can lead to component integration saving in fabrication time and costs. The shapes and parts that can be made in composites can sometimes not be so readily possible or achievable in metals.
When comparing the specific stiffness (Young's Modulus divided by density) of steel and aluminium alloy we get a figure of 27,and titanium 24. With a well aligned carbon fibre (graphite fiber)/epoxy the figure is 87. A factor of 3. Even with mixed fibre alignment of 0 and +-45 the figure is 50 a factor of 2.
When comparing the specific strength (tensile strength divided by density) of steel 140, aluminium alloy 125, titanium alloy 178. Where as a well aligned carbon fibre (graphite fiber)/epoxy is 870. A factor of between 5 to 7 times. Even with mixed fibre alignment of 0 and +-45 the figure is 500 giving a factor in the range of 3 - 4 times greater. This demonstrates the potential weight savings when using composite materials.
It is true that kg for kg composite materials may appear expensive but you actually need less mass. Very often the tooling costs of composites compared to sheet metal presses
for lets say automotive panels are considerably less when looking at production runs of up to several thousands.
Even more weight can be saved and bending stiffness much increased once sandwich structures are utilised. That is a skin of fibre reinforced plastics (FRP) each side of a core material such as aluminium honeycomb or a structural foam such as PMI (trademark Rohacell). Once again we can have moulded shapes. Metallic sandwich structures
are possible but usually are only flat or single curvature panels.
With fibre reinforced plastics (FRP) the laminate can be tailored in different fibre directions and in the form of uni directional (aligned fibres) or fabric to suit stress paths.
Also we can choose from a wide array of fibres that can be employed whether variables of high strength, intermediate and high modulus carbon fibres, Or others such as
Aramid (kevlar), E- and S- glass, Zylon (PBO) Dyneema/Spectra (HDPE) and Boron. We can use hybrid fabrics of the aforementioned fibres and also mix materials within a
laminate to utilise to the best advantage of the properties of each type of fibre.