Liquid composite molding of tackified fiber preforms

Successful molding of tackified preforms with minimum defects in cured composite parts, requires a thorough understanding of key process issues such as preform springback, permeability, mold filling, fiber wetting, and tackifier compatibility with the matrix resin. These issues are investigated in this work using bismaleimide (BASF's BMI 5250-4 RTM) and 3M's epoxy (PT 500) resin based reactive tackifiers and polymethylmethacrylate (PMMA) based non-reactive tackifier. Results obtained show that material and process variables such as, tackifier type, concentration, size, extent of tackifier cure during preforming, application method (solvent vs. powder) and tackifier distribution (between the fiber layers vs. within the fiber tows), play important roles in governing the moldability of tackified preforms.