A Model for Fiber Length Attrition in Injection-Molded Long-Fiber Composites

Journal Article · Tue Jan 01 00:00:00 EST 2013 · Composites Part A: Applied Science and Manufacturing

OSTI ID:1158733

TuckerIII, Charles L. ^[1]; Phelps, Jay H ^[1]; El-Rahman, Ahmed Abd ^[1]; Kunc, Vlastimil ^[2]

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1. University of Illinois, Urbana-Champaign
2. ORNL

Long-fiber thermoplastic (LFT) composites consist of an engineering thermoplastic matrix with glass or carbon reinforcing fibers that are initially 10 to 13 mm long. When an LFT is injection molded, flow during mold filling orients the fibers and degrades the fiber length. Fiber orientation models for injection molding are well developed, and special orientation models for LFTs have been developed. Here we present a detailed quantitative model for fiber length attrition in a flowing fiber suspension. The model tracks a discrete fiber length distribution (FLD) at each spatial node. Key equations are a conservation equation for total fiber length, and a breakage rate equation. The breakage rate is based on buckling of fibers due to hydrodynamic forces, when the fibers are in unfavorable orientations. The FLD model is combined with a mold filling simulation to predict spatial and temporal variations in fiber length distribution in a mold cavity during filling. The predictions compare well to experiments on a glassfiber/ PP LFT molding. Fiber length distributions predicted by the model are easily incorporated into micromechanics models to predict the stress-strain behavior of molded LFT materials. Author to whom correspondence should be addressed; electronic mail: [e-mail] 1

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1158733
• Journal Information: Composites Part A: Applied Science and Manufacturing, Vol. 51, Issue 0
• Country of Publication: United States
• Language: English