Impact toughness of cellulose-fiber reinforced polypropylene : influence of microstructure in laminates and injection molded composites

Abstract

Unlike their glass reinforced counterparts, microstructure and dynamic fracture behavior of natural fiber-reinforced thermoplastics have hardly been investigated. Here, we characterize the microstructure of cellulose fiber-reinforced polypropylene and determined its effect on impact toughness. Fiber lengths were reduced by one-half when compounded in a high-intensity thermokinetic mixer and then injection molded. At low fiber contents, injection molded specimens showed little fiber orientation; at high fiber contents, a layered structure arose exhibiting differing fiber orientations through the specimen thickness. To better control composite microstructure and understand its influence on impact toughness, model laminates containing aligned fibers were produced and tested. Instrumented Charpy impact tests were performed and analyzed using linear elastic fracture mechanics. Dynamic critical energy release rates and dynamic critical stress intensity factors increased with cellulose content and with orientation of fibers perpendicular to the crack plane. Preliminary evaluation of a simple model relating the microstructure to the dynamic fracture toughness for both injection molded composites and laminates showed promise.

Citation

Clemons, Craig; Caulfield, Daniel; Giacomin, A. Jeffrey. 2003. Impact toughness of cellulose-fiber reinforced polypropylene : influence of microstructure in laminates and injection molded composites. Seventh International Conference on Woodfiber-Plastic Composites (and other natural fibers), May 19-20, 2003 ... Madison, Wisconsin, USA. Madison, WI : Forest Products Society, 2003: Pages 119-125