Stress Residual

Residual stresses can have important consequences for the manufacture and the resulting properties of polymeric, metallic, and ceramic matrix composite materials and components. Because of the different mechanical, thermal, and shrinkage properties of the fibers and matrices, as well as the anisotropy of the constituent laminate, residual stresses can have many different origins and can arise at the matrix/fiber level, between plies and at the macroscale component level. Here, the origin of thermal stresses, shrinkage stresses, curing stresses, tooling-induced stresses, environmental stresses, and loading-induced residual stresses are considered. Furthermore, the means of quantifying such stresses by mechanical and nonmechanical methods across the various scales are described, including the use of embedded sensors. The implications of these different residual stresses are evaluated in terms of the matrix properties, distortion, transverse ply cracking, and thermal ratcheting. Finally, strategies for manipulating and controlling residual stresses are discussed centered on composite design, methods to delay the onset of transverse ply cracking, and via the use of heat treatments. Finally, the future opportunities for metal, ceramic, and polymer matrix composites as well as smart composite systems are discussed along with the emergence of 3D woven, stitched, and damage tolerant fiber architectures.