Assessing glass-fiber modification developments by comparison of glass-fiber epoxy composites with reference materials: Some thoughts on relevance

Any approach for designing composites with improved mechanical properties finally has to be assessed for respective improvements achieved. Glass-fiber reinforced epoxy matrix laminates consist of several constituents. Pretreatment of the constituents, the processes combining the matrix with the reinforcing fibers as well as the curing of the laminate may all have an effect on the resulting mechanical or fracture properties of the composites. In this contribution, the authors present selected cases from recent materials developments, dealing with glass-fiber epoxy laminates for which a thermal fiber treatment for desizing was compared with chemical solvent desizing. While desizing with a solvent and resizing with another type of sizing yielded tensile and interlaminar shear properties comparable to those of laminates prepared from as-received fibers, but lower for desized fibers, resizing after thermal desizing treatment exceeding +500 ℃ yielded lower properties for laminates from desized and resized fibers, but roughly in the same percentage difference as chemically desized and resized fiber laminates. This raises the question of how material or interface modifications in glass-fiber epoxy composites can best be compared for an assessment of the improvements achieved by the fiber treatments or the fiber–matrix interface modifications.