Welding in the World

, Volume 62, Issue 6, pp 1301–1309 | Cite as

Influence of fiber orientation and weld position in welding injection-molded fiber-reinforced thermoplastics

  • Isabel Fiebig
  • Volker Schoeppner
Research Paper


Several publications deal with the influence of the initial fiber orientation in joining parts on the weld strength of fiber-reinforced thermoplastics. The welding partners have been sawn before welding. Preparing the joining parts after injection molding is not suitable since it is an additional manufacturing step. Since injection molding results in a non-uniform fiber orientation, there is a possibility that the position of the weld influences weld characteristics. The influence of the initial fiber orientation was investigated by preparing parts with longitudinal or transverse initial fiber orientation. Short and long glass fiber-reinforced thermoplastics with a glass fiber content of 30% have been welded by hot-plate and vibration welding. The initial fiber orientation in non-welded parts influences the weld strength: longitudinal fibers are more advantageous for the weld strength than transverse fibers. The influence of the position of the weld in injection-molded parts was investigated by welding the plates at the end of the flow path, at the sawn gate, and at the lateral side. The weld strength is similar at the gate or at the end of the flow path. For PA-GF30, the weld strength at the gate is even higher. Positioning the weld at the lateral side in injection-molded parts results in significantly lower weld strengths for short and long glass fiber-reinforced thermoplastics in hot-plate and vibration welding.


Polymer joining Fiber reinforced thermoplastics Composites Vibration welding Heated tool welding 

Symbol list




Acrylonitrile butadiene styrene

axx, ayy, azz

Component of orientation tensor


Computed tomography




German Welding Association


Fiber-reinforced plastics


Glass fiber-reinforced


Hot plate (welding)


Long glass fiber-reinforced


Melt-layer thickness after heating


Unit vector






Welding pressure

px, py, pz

Component of the unit vector P


Region of interest


Joining displacement


Hot-plate temperature


Joining velocity


Vibration welding


Weld strength



The IGF Project 18702 N of the research association “Forschungsvereinigung Schweißen und verwandte Verfahren e. V. des DVS. Aachener Straße 172. 40223 Düsseldorf” was on the basis of a resolution of the German Bundestag, promoted by the German Ministry of Economic Affairs and Energy via AiF within the framework of the program for the promotion of joint industrial research and development (IGF).


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Copyright information

© International Institute of Welding 2018

Authors and Affiliations

  1. 1.Kunststofftechnik PaderbornPaderborn UniversityPaderbornGermany

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