Use of Composites for Aircraft Primary Structural Components

In today's commercial aviation world, airlines have for a long time understood the importance of flying an aircraft as economically as possible. Advances in technology have made this possible in a number of ways, one of which is the introduction of composite material use wherever feasible. Composite materials typically offer a weight saving of between 20 and 25% when used in place of historically manufactured components made predominantly from alloyed metals. The heavier the aircraft, the more fuel it burns for a given mission, making weight reduction top priority for aircraft designers. The non-corrosive benefits, high-energy absorption and resistance to fatigue offered by composites are another attractive feature, but despite this and the favourable strength to weight ratio, they aren't the miracle solution for all aircraft structures. Composites can be difficult to inspect for flaws, some absorb moisture, which compromises their structural integrity. The fabrication process is often complex and labour intensive, requiring the use of specialist equipment and expertise thus making utilization cost prohibitive.

In its most primitive form a composite material consists of two dissimilar materials, one being the matrix and the other the reinforcement. These materials are selected so as to mechanically compliment one another whilst neutralising their deficiencies. The reinforcement may have high strength in tension, but little resistance to bending and compressive forces, the matrix may on the other hand have high resistance to bending and compressive forces, so when used together, produce a composite with both high tensile and compressive strengths and also a high resistance to bending. The matrix binds together the reinforcement, which is usually in the form of rods, strands, fibres or particles and is much stronger and stiffer than the matrix, this results in the reinforcement being held in an orderly pattern and because the reinforcements are usually

References: design_guidelines/test_series/1422msfc.pdf http://www.qmi-inc.com/Ultrasonic%20Air-Coupled%20Inspection%20of%20Advanced%20Material.htm Word Count - 1895, not including titles, quotations, references and bibliography.