Moisture-matrix interactions in polymer based composite materials

Fiber reinforced polymeric composites are currently based both on thermoset polymers like epoxy or polyester resins and on advanced thermoplastic materials like polyetheretherketone (PEEK), polyetherimide (PEI) and polysulfone (PSU). Sensitivity of polymer matrices to the presence of moisture and solvents and to thermally induced stresses is of primary importance in determining the durability of polymer based composite structures. In fact, moisture and solvents can greatly affect not only mechanical properties of the matrix per se, but also its adhesion properties to the reinforcing fibers. The mechanisms through which sorbed moisture and solvents can act are reviewed in this paper. These mechanisms include interaction with specific groups and penetrant induced plasticization and are deeply examined in the case of epoxy, polyester and PEEK resins.