Introduction to Aerospace Materials

22

Creep of aerospace materials

22.1 Introduction

Creep is a process that involves the gradual plastic deformation of a material over time. The remarkable thing about creep is that plastic deformation occurs at stress levels below the yield strength of the material. In other words, creep causes a material to plastically deform and permanently change shape over time when subjected to an elastic load. This runs counter to the concept that plastic deformation can only occur when the applied stress exceeds the yield strength of the material.

When most engineering materials, including the metal alloys and composites used in aircraft structures, are elastically loaded then the amount of deformation that occurs does not change with time. However, ...