Improved associated flow rule for anisotropic viscoplasticity in thermoplastic polymer systems

An elasto-viscoplastic constitutive model was previously developed and successfully used to describe the anisotropic time-dependent response of short fiber reinforced thermoplastics. It is demonstrated that when it applied systems with a higher level anisotropy, apparent anisotropy rate-dependent yield stress deviates from Hill parameters are define it. This becomes more if increased. The origin this discrepancy mathematically investigated shown be related viscoplastic multiplier associated flow rule employed. A solution proposed completely restores consistency extends applicability high anisotropy. • for evaluated highly systems. Inconsistencies in case levels identified. improved