Category: Uncategorized

Creep is a plastic deformation process that occurs when materials are subjected to elastic loading for a long period of time, often at high temperature. Engineering materials do not plastically deform when loaded within the elastic regime for short times. However, when the elastic load is applied for a sufficient period the material eventually deforms…

Fatigue tests measure the resistance of materials to damage, strength loss and failure under the repeated application of load. Aerospace materials must withstand repeated loading for long periods of time, which is in the order of 15 000–20 000 flight hours for modern jet engine materials and anywhere from 80 000 to 120 000 h for…

Fibre–polymer composites are susceptible to damage from impact events such as bird strike, dropped tools during aircraft maintenance, tarmac debris kicked-up by the wheels during take-off or landing, and large hail stones. Impact testing is performed at different impact energy levels to screen composite materials for damage resistance and damage tolerance. The most common and…

Fracture toughness is an engineering property that defines the resistance of a material against cracking. Tough materials require large amounts of energy to crack whereas low toughness materials have little resistance against cracking. For the materials used in aircraft structures, fracture toughness is just as important as other mechanical properties such as elastic modulus and…

Simply stated, hardness is the resistance of a material to permanent indentation. Hardness is not a precisely defined engineering property, such as elastic modulus or yield strength, but it is still widely used to describe the resistance of materials to plastic deformation. The hardness of ductile materials is related to their yield strength, and the…

The flexure test measures the mechanical properties of materials when subjected to bending load. A flat rectangular specimen is loaded at three or four points, as shown in Fig. 5.14. The load causes the specimen to flex, thus inducing a compressive strain on the concave side, tensile strain on the convex side, and shear along the mid-plane.…

The compression test determines the mechanical properties of materials under crushing loads. There are many aircraft structures that carry compression loads, such as the undercarriage during take-off and landing or the upper wing surface during flight, and therefore the mechanical behaviour of their materials must be determined by compression testing. It is often assumed that…

Basics of the tension test The tension test is one of the most common and important methods for measuring the mechanical properties of materials. The tension test is popular because a large number of properties can be determined in a single test: elastic modulus, strength, ductility, and other properties. The test is also popular because it…

The selection of materials for aircraft structures and engines is assessed according to a multitude of parameters such as cost, ease of manufacture, weight and a host of other factors. Central to the selection of materials is their mechanical properties such as stiffness, strength, fatigue resistance and creep performance. The durability properties of structural and…