Long term behaviour of CFRP laminates: an experimental test

In the past few years, the strengthening of concrete structures with externally epoxy-bonded fiber reinforced polymer (FRP) composites is becoming increasingly user-friendly among engineers worldwide. One of the most relevant topics is represented by the durability and the reliability of this technique, closely related to the time-depending behaviour of composite materials. In fact, these materials are made up of a matrix, highly sensitive to creep, and of purely elastic fibers. In particular, as it usually happens when dealing with aged concrete structures, the viscous deformations of the concrete can be considered ended. Consequently, only FRP creep deformations have to be accounted. A similar problem occurs in the case of the steel-concrete composite structures: in this case creep phenomena only concern the concrete component, while the steel component does not flow […]. A wrong evaluation of viscous effects could introduce relevant errors in the design of the structural plating. At the moment, literature does not provide any final conclusion […] on this important topic. Furthermore, studies developed in the aeronautic or naval field and dealing with the creep properties of composite materials cannot be directly used for civil engineering purposes, mainly because of the different technological processing of these materials. From a practical point of view, guide lines and technical codes introduce only stress limitations in order to make safe composite structures in presence of viscous effects […]. The aim of the paper is to show some results on the creep behaviour of a CFRP laminate investigated by a specific approach, as follows. These results belong to a main experimental program going on at University of Salerno