Material Characteristics and Structural Health Monitoring of Fiber Metal Laminates

Abstract FMLs have been investigated in various combinations of FRPs and metals. Due to their layered structure, they exhibit superior damage tolerance and fatigue resistance. However, significant differences in the coefficients of thermal expansion between FRP and metal result in interlaminar residual stresses between the single layers of the FML. The literature discusses different methods to reduce these residual stresses, from which the modification of the cure cycle shows superior potential. Previous research on composite materials indicates that SHM using GUWs is a promising method for damage assessment in FMLs. Due to the dependencies of stresses and the wave propagation velocity of GUWs, as well as the influence of residual stresses on the fatigue behavior of FMLs, it is assumed that, in particular, two subtasks of an SHM system are most likely to be affected by a residual stress state in an FML. The focused literature study identifies open research questions in the interaction of FMLs with SHM that are the basis to formulate precise research hypotheses and the structure of this doctoral thesis.