Mechanical analysis of PA66 under combined shear–compression

The large-strain mechanical behavior of PA66 was investigated using shear–compression specimens (SCS) with two opposite slots machined at different angles (15°, 30°, 45°, and 50°). Results show that strain rate and slot angle affect the equivalent stress in different levels. Slot angle sensitivity affects both flow stress and hardening characteristics, and strain rate influences elastic deformation. Increasing the strain rate gradually increases the equivalent stress. SCS with a slot angle of 30° exhibits the largest equivalent stress and the greatest effect of strain rate. The stress–strain curve differs between cylindrical specimens and SCS under quasi-static conditions. The yield stress obtained by the cylindrical specimens is higher than that of SCS. A constitutive model is modified based on the Drucker–Prager criterion to describe the effect of hydrostatic pressure and strain rate on the equivalent yield stress of polymer materials. The theoretical formula predictions are consistent with experimental results, thereby confirming the feasibility of this constitutive relationship.