Composite materials offer higher specific strength and stiffness than other conventional materials. Readily available carbon fibre composites will match the stiffness and strength of high-grade aluminium in all directions, at less than two-thirds the density. Specialist grades can be double the strength and stiffness of steel in the fibre direction at a fifth of the density.

Excellent strength and stiffness to weight ratio
The relative lightness of composite materials enables use of bigger sections that are inherently stiffer and stronger for bending and torsion. This is a considerable advantage for engineered structures.   On a basic box section Aluminum, Titanium and Steel have very similar specific strength and stiffness which can be exceeded by even Black Metal application of carbon fibre composites.  Tailoring the direction of the fibres to where they work efficiently can give 4 times stiffer or 2.5 times stronger per weight.  Tapering the lay-up or increase the aspect ratio of the section improves performance further and can yield stiffness at 20 times and strength four times than the metallic baseline.
Ability to form complex shapes
Composites can be used to make complex shapes without using high pressure tools, because the composite is formed when the matrix cures or goes solid. Consequently, the geometry of the part is very flexible, whether produced in low volume by manual lay-up pre-preg cured in a press or autoclave or using dry fibre performs infused with liquid resin in a closed mould.
The ability to mould  complex shapes allows greater potential for consolidating the number of individual components in an assembly and structurally offers the advantage of inherent stability and buckling resistance.  The use of core materials can further enhance the out of plane stiffness and moves composites into a different league.
Composites offer outstanding fatigue and durability  potential and are in general very tolerant to environmental effects such as UV damage, moisture, chemical attack and temperature extremes.
Damping characteristics
Composites have the ability to reduce induced vibrations rapidly.