Application of statistic estimation to weldline strength of injection-molded thermoplastic composites

Shih Jung Liu*, Chang Yao Yang

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

6 Scopus citations


The injection molding of thermoplastic composite materials has become an important process in industry, due to the possibility of producing near shape article having exceptional physical and mechanical properties. However there are still some problems that confound the overall success of this technology. The forming of weldlines wherever polymer flow fronts meet is one of them. In this report, an L'18 experimental matrix design based on the Taguchi method was conducted to study the effect of different processing parameters on the weldline strength of injection-molded thermoplastic composites. Experiments were carried out on a 4.1 oz reciprocating injection molding machine. The materials used were acrylonitrile-butadiene-styrene, and 20 and 30% glass-fiber-filled ABS composites. A plate cavity with an obstacle in the center was used to create a weldline. After molding, the weldline strength of the composites was determined by a tensile tester. Various processing variables were studied in terms of their influence on the weldline strength of injection-molded composites: melt temperature, mold temperature, melt filling speed, melt filling pressure, packing pressure, and size of the obstacle. For the factors selected in the experiments, size of obstacle and melt temperature were found to be the important parameters affecting the weldline strengths of injection-molded composites. The weldline strength of virgin material increased with the distance from the obstacle, while the weldline strength of composites decreased with the distance.

Original languageEnglish
Pages (from-to)1383-1396
Number of pages14
JournalJournal of Reinforced Plastics and Composites
Issue number13
StatePublished - 2004


  • ABS composites
  • Injection molding
  • Processing parameters
  • Weldline strength


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