Intra-ply shear characterization of unidirectional fiber reinforced thermoplastic tape using the bias extension method

Dennis Brands*, Wouter Grouve, Sebastiaan Wijskamp, Remko Akkerman

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

5 Citations (Scopus)
69 Downloads (Pure)


Press forming of thermoplastic unidirectional (UD) carbon fiber reinforced laminates is an attractive production method in the aerospace industry for cost-effective manufacturing of high-performance parts. The possible formation of wrinkling defects in the formed parts has led to the development of predictive, finite element based, process simulation tools. The material behavior during the forming process is described based on the governing deformation mechanisms, being intra-ply shear, inter-ply and tool-ply slippage and bending. Intra-ply shear is especially important when forming parts having double curvature. The intra-ply shear behavior of fabric-based composite materials is often characterized using the bias extension method but has not successfully been applied to thermoplastic UD tapes yet. This work describes the application of bias extension experiments on cross-ply UD laminates at forming conditions to characterize the intra-ply shear material behavior. The test procedure was designed to prevent deconsolidation and improve load introduction, promoting specimen integrity and reduce shear buckling during testing. Preliminary results show that the material exhibits rate-dependent behavior. A video extensometer was used to measure the shear deformation in the center of the specimen. Additionally, a deformation analysis was performed using a grid of lines on the specimen, where the theoretical areas of constant shear according to a pin-jointed net can be recognized but are not fully uniform. In particular, shear banding parallel to the fiber direction is observed on the outer ply at a length scale below the grid size used for the deformation analysis suggesting a yield point and softening behavior on the meso scale which is not directly evident from the macroscopic response.

Original languageEnglish
Title of host publicationESAFORM 2021 - 24th International Conference on Material Forming
PublisherPoPuPS (University of LiFge Library)
ISBN (Electronic)9782870193020
Publication statusPublished - 2021
Event24th International Conference on Material Forming, ESAFORM 2021: Friction and wear in forming processes - Online Event, Belgium
Duration: 14 Apr 202116 Apr 2021
Conference number: 24


Conference24th International Conference on Material Forming, ESAFORM 2021
Abbreviated titleESAFORM 2021
CityOnline Event
Internet address


  • Bias extension
  • Carbon fiber
  • Characterization
  • Composite forming
  • Intra-ply shear
  • Thermoplastic
  • Unidirectional


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