Characterisation and modelling friction at the tool-ply interface for thermoplastic woven composites
Press forming of thermoplastic textile composites is a 
fast and efficient method of production. Friction 
occurring between the composite material and pressure 
blank-holder during forming imparts tensile stresses in 
the sheet which help counteract compressive stresses 
generated by material deformation; stresses that can 
result in unwanted wrinkling of the forming sheet. In 
order to model the press forming process and optimise 
boundary conditions, this friction behaviour must be 
characterised and modelled. Two different test methods 
are employed to characterise the friction and two 
complementary modelling strategies, an empirical and a 
predictive approach, are presented.
Modeling of Friction and Shear in Thermostamping of Composites - Part I
The effects of processing parameters on the friction coefficient between commingled glass-polypropylene plain-weave fabric composites (Twintex) and the steel tool during thermostamping processes are under investigation. This work focuses on the effect of fiber orientation, fabric velocity, normal force, and resin viscosity (through variations in tool and fabric temperatures) under conditions similar to those in the thermostamping processes. In comparison to the experiments conducted to date, velocity, normal force, and tool temperature have the greatest effect on the friction coefficient. The effect of tool temperature on the friction coefficient dominated the effect of initial fabric temperature on the friction coefficient. Based on the effect of these parameters, a phenomenological model has been incorporated into ABAQUS/Standard as a user-supplied friction subroutine. This model was first used in a finite element model of the friction test. A good agreement was found between the experimentally measured friction force and the numerically calculated one.
Joint strength of aluminum ultrasonic soldered under liquidus temperature of Sn–Zn hypereutectic solder
Abstract In order to obtain high-strength aluminum joints, ultrasonic soldering of 1070 aluminum was conducted under liquidus temperature of Sn–Zn hypereutectic solder. A device for ultrasonic soldering was assembled, which propagated ultrasonic vibrations in a direction perpendicular to joining surfaces. This device joined 1070-Al using quasi-melting Sn–Zn hypereutectic solder without using any artificial spacers. The strength of the solder joints was evaluated by tensile tests. The optimum joining conditions were determined, and the effects of solder compositions and soldering temperature on the joint strength and the solder layer thickness were examined. In this ultrasonic soldering process, the highest tensile strength was obtained for the solder joints fabricated at 220 °C for the Sn–23Zn and Sn–40Zn solder compositions. The joint strength was equivalent to that of 1070-Al heat treated at 220 °C. The sound joints were obtained at 300 °C using Sn–82Zn solder, the liquid phase volume fraction of which was theoretically only 0.24. The present work also revealed that the thickness of retained solder layer in the joint after ultrasonic soldering could be estimated. Accordingly, ultrasonic soldering under the liquidus temperature of Sn–Zn hypereutectic solder could be a spacer-free soldering method to obtain high-strength aluminum joints.