Effect of moisture on elastic and viscoelastic properties of fiber reinforced plastics: Retrospective and current trends

This chapter is a brief review of journal papers and books about moisture and composites with polymer matrix (mostly fiber reinforced composites but not exclusively). Most polymer materials and composites absorb moisture. It is well known from many papers (some of them mentioned in this chapter) over several decades that absorbed moisture essentially affects mechanical and many other important properties of polymers and polymer-based composites. The key question is: How does absorbed moisture affect mechanical properties of composites? Furthermore, the process of moisture absorption in composite structures may occur over many months and even years. More questions then arise: What is the mechanism of moisture absorption in a polymer composite, how long can this process last, and how much moisture can be absorbed? Looking through recent journal papers, it may be concluded that many of them use a classical theoretical approach that has been known and used for many decades. Some authors apply this classical approach to investigate moisture absorption and its effect on the mechanical properties of new materials such as, for example, nanomodified polymers. It would be useful and important to obtain new knowledge about these new materials but, unfortunately, quite often authors do not investigate the effects of moisture any deeper than was done 40 years ago. This chapter looks at new research as well as the classical research addressing this area.