A simulation study on the effects of particle size on the consolidation of polymer powder impregnated tapes S. Padaki, L.T. Drzal * Composite Materials and Structures Center, Department of Chemical Engineering, Michigan State University, East Lansing, MI 48824-1326, USA Accepted 17 June 1998 Abstract The powder prepreg technique offers a low-cost, high-speed method of manufacture of composites. Consolidation of the prepreg tows is a key step in the manufacture of a final ‘useful’ part. The efficiency of the consolidation for any polymer powder prepreg tape produced from a powder prepreg process would conceivably depend on the material properties of the polymer, particle size, temperature, consolidation pressure, and volume fraction of the tape. A mathematical process model that identifies and describes a set of parameters to predict the consolidation conditions of a given polymer powder prepreg tape has been developed. A simulation study that identifies the different parameters and compares the advantages and limitations of polymer physical properties and particle size has been performed. An integrated Flow Resistance (FR) Index has been developed to mathematically describe the consolidation process. The results show that small powder particle sizes are beneficial to the process.  1999 Published by Elsevier Science Ltd. All rights reserved. Keywords: A. Tape; A. Prepreg; Particle size 1. Introduction Composite materials have gained acceptance as replace- ments for traditional structural materials in many of today’s industries. Their excellent strength to weight ratio benefits are being widely utilized, producing more fuel efficient ground transportation systems, superior recreational goods and higher performance aerospace vehicles. Polymer matrix composites have an aerospace history which emphasized high structural performance with cost being a secondary consideration. Durable goods (transportation, appliance, construction, etc.), infrastructure (bridges, decking, etc.) and off-shore oil platform applications, promise to increase the use of polymer composite materials by several times if lower cost and environmentally safe processing methods can be found to manufacture these materials. Conventional proces- sing methods rely on long process cycles and/or use of toxic solvents. These aid the processability but result in higher monetary and environmental costs. Polymers used as matrices in composites can be broadly classified into two categories—thermosets and thermoplas- tics. Of the two, thermosets have traditionally dominated the polymer composite industry. In recent years, there has been an increasing interest in the use of thermoplastic matrices for composite applications. High strain-to-failure, increased fracture toughness, better impact tolerance, shorter molding cycles, infinite prepreg shelf life, recyclability and repar- ability are some of the potential reasons for the growing interest in their development. However, applications of ther- moplastic matrix composites have been limited due to the difficulty in fabrication arising essentially from their high melt viscosities. Many approaches have been developed for the processing of thermoplastic composites. These include the following. • Solution processing —dissolving the resin in a suitable solvent and impregnating the tow with dilute solution which is later processed to remove solvent [1]. • Melt impregnation —forcing molten polymer into a fiber tow to form a prepreg tape [2]. • Film stacking —compacting alternate layers of fiber with thin sheets of resin [3]. • Filament bundle coating —sheathing small filament bundles with the thermoplastic polymer [4]. • Co-mingling —weaving together reinforcing fibers with thermoplastic matrix fibers to get a shapeable fabric [5]. • Slurry processing —drawing the fiber tow through a suspension of solid, small polymer particles suspended in a liquid carrier [6]. Composites: Part A 30 (1999) 325–337 1359-835X/99/$ - see front matter  1999 Published by Elsevier Science Ltd. All rights reserved. PII: S1359-835X(98)00115-8 * Corresponding author.