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New publication on the prediction of ply-ply friction for simulation software

New publication on the prediction of ply-ply friction for simulation software
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1 minute, 40 secondes

Excessive resistance against the movement of adjacent plies, or ply-ply friction, can lead to process-induced defects during hot press forming of thermoplastic composite laminates. To avoid the occurrence of defects on beforehand, use can be made of process simulations. However, a good understanding of the ply-ply friction is required to improve the constitutive models to allow for simulation of more complex parts.

Rens performed friction experiments on UD C/PAEK tapes, showing a typical response with a peak followed by a steady-state friction. The peak shear stress was successfully predicted by assuming a shear flow of the matrix material in the ply-ply interface, for which he measured the matrix viscosity and analyzed the matrix interlayer in the ply-ply interface.

Schematic illustration of a ply-ply interface (upper-left corner) of two adjacent plies separated by the x-axis. The fiber edges (dashed lines) results in a matrix interlayer thickness distribution h(x), as illustrated in the upper graph. Movement of the top ply along the z-axis (fiber direction) results in a local shear rate (upper-right corner) and, due to h(x), a distribution of shear rates (middle graph). Consequently, a shear stress distribution appears when a certain matrix viscosity is considered as illustrated in the lower graph. The dashed grey line reflects the onset of strong slip in the fiber-matrix interface, which limits the viscous shear stress. Integration of the shear stress distribution with and without slip yields an accurate prediction of the measured peak and long-time friction response.

Further, Rens accurately described the steady-state friction by including a critical shear stress to represent wall slip, substantiating the concept of wall slip as the dominant underlying mechanism for the start-up friction response. These new insights will be used as a basis for future constitutive modeling of ply-ply friction. In the end, a better description of friction will improve the predictive capabilities of simulation software on defect generation during hot press forming to enable first-time-right defect-free manufacturing.

Rens has performed this research at the TPRC in close cooperation with the Production Technology research group of Remko Akkerman from the University of Twente. NWO (Dutch Research Council) financed and supported this research project.

The complete publication is available on Science Direct here.

More information www.tprc.nl