Publisher's Synopsis
Complex advances in metallic and non-metallic manufacturing deliver real value for key stakeholders involved in the aerospace industry. The requirement for original equipment manufacturers to deliver lighter, stronger and more durable and damage-tolerant airframes powers this growth forward. It means innovative solutions have been developed through improvements to metallic alloys, as well as breaking new ground in the creation of new non-metallic composite materials. But as more is demanded from these materials, and as new types of materials are being created, assessing and characterizing their properties to predict their failure becomes more challenging. What is particularly significant in the race for fuel efficiency delivered by lighter components is the interplay between metallic and non-metallic, with a real race going on. Short-to-medium term gains are set to be made from advances in metallic, such as titanium and aluminum-lithium alloys. However, there is the potential for the eventual ascendancy of non-metallic composite materials, as their properties become more easily predicted and characterized. Whatever these comparative advances, it is not enough to merely know the basic properties of a material, so durability and damage tolerance is crucial. All aerospace vehicles must be designed to be durable and damage tolerant. Durability is an economic life-cycle design consideration whereas durable and damage tolerant relates to a structure's ability to safely sustain defects until they are removed or repaired. Durable and damage tolerant is based on the assumption that undetectable cracks that grow during service are present in each fracture critical component at the most critical location. Hence, OEMs use fracture mechanics methods to help design the aircraft. Fracture mechanics is the study of crack propagation in materials and relies on fatigue crack propagation and fracture toughness testing. When a material is subjected to repeated loading and unloading, fatigue occurs. Fatigue crack propagation measures fatigue crack growth rate versus change in crack tip stress intensity. When a crack grows to a critical size, it has reached its critical fracture toughness or stress intensity and catastrophic failure occurs. In general terms, durability relates to fatigue crack propagation and damage tolerance relates to fracture toughness.
