Friction-Riveted Hybrid Joints of Short Glass Fiber-Reinforced Polyamide 6 and 6056-T6 Aluminum Alloy

Hybrid joints of short glass fiber-reinforced polyamide 6 and 6056-T6
aluminum alloy (PA6-30GF/AA6056-T6) are produced by friction riveting
under different processing conditions. A comprehensive study of the effects of
the processing parameters on the temperature evolution, anchoring efficiency,
degradation of the polymer composite, and tensile strength (pullout test) of
the joints is performed. With higher values for the rotational speed, spindle
displacement, and joining force, the heat input is increased and this results in
greater deformation of the rivet tip and thus higher anchoring efficiency. Based
on this finding, high-strength joints with tensile strength (pullout test) of up
to 93% of the metal rivet are obtained and failure occurred through the ductile
fracture of the metal rivet outside the composite plate region. Process-related
degradation of the polymer composite is identified, with the formation of
voids in the polymer thermo-mechanically affected zone (PTMAZ) as well as
PA6 chain scission and glass fiber breakage in the rubbing volume around the
rivet. The recrystallization of the PA6 matrix in the PTMAZ is not affected by
the processing. Degradation of the composite at the polymer-metal interface
does not reduce the quasi-static tensile strength (pullout test), although it
may affect the long-term mechanical properties of the joint.