A study of friction between composite-steel surfaces at high impact velocities

• Study of friction in dynamic tests.
• Dynamic friction in composite materials at high impact loads.
• Correction of errors generated by wave dispersion in Hopkinson bar.

The Hopkinson Split Pressure Bar system allows to carry out compression tests at high impact velocities corresponding to high strain rates up to 5000 s−1. For composite materials, however, negative phenomena related to wave propagation and specimen geometry may disturb experimental analysis and, therefore, should be taken into account. Potential errors are mainly due to friction, inertia and wave dispersion. In order to provide a complete analysis of experimental results for composite materials under dynamic compression, a procedure was developed to estimate friction and dispersion effects at the specimen-bar contact zone. For this purpose, dynamic tests were carried out on woven glass-fiber-reinforced Polyamide (PA6) composites using Hopkinson׳s bar and pin-on-disk tribometer tests techniques. Results showed that the state of friction characterizing the PA6/glass material differs as per the orientation of fibers. The frictional regime is relatively more severe in case where the fibers are normal to the direction of friction.