Session: 03-11-01: Thermoplastic Composites

Paper Number: 121606

121606 - An Implicit Integration Scheme for Nonlinear Viscoelastic–viscoplastic Polymers 

Thin-ply high strain composites (TP-HSCs) are widely used in deployable compositebooms thanks to their high strength-to-weight ratios, low manufacturing costs, and ability to sustain large curvatures without failure. Despite these advantages, TP-HSCs in composite booms may be degraded by different mechanisms during boom coiling and stowage, and the composite booms only partially recover their cross-sections when deployed. It is critical but challenging to predict the extent of viscoplastic deformation/stress relaxation in a TP-HSC. However, there is still a need for a constitutive model for the resin matrix exhibiting material and geometric nonlinearities in practice. The objective of this paper is to develop an implicit integration scheme for nonlinear viscoelastic–viscoplastic polymers. The Shapery nonlinear viscoelasticity model, along with an implicit integration scheme, is reformulated to facilitate its integration with a viscoplasticity model. A viscoplasticity model, which consists of the Drucker–Prager yield function, nonlinear isotropic and kinematic hardening laws, and the Perzyna viscosity function, is subsequently constructed. The nonlinear viscoelasticity and the viscoplasticity models are then implemented in an implicit integration scheme. A closed-form algorithmic tangent operator is derived to facilitate model implementation. The present integration scheme is validated by calibrating the viscoelastic and viscoplastic parameters of polymethyl methacrylate (PMMA) and high-density polyethylene from test data, respectively. It is found to be capable of reproducing a wide variety of test data. It can be implemented in a multiscale modeling framework for the multiscale analysis of TP-HSCs.

Presenting Author: Liang Zhang AnalySwift LLC

Presenting Author Biography: Senior Research Scientist at AnalySwift, Dr. Liang Zhang earned his PhD in Mechanical Engineering from Texas A&M University in 2011. His expertise lies in nonlinear homogenization of composites, plasticity, damage, fracture, and fatigue. Dr. Zhang has authored over 20 journal articles and conference proceedings. Additionally, he has successfully undertaken several projects, including NASA STTR, Air Force STTR, and Army Research Laboratory initiatives.