Cyclic viscoelastoplasticity and low-cycle fatigue of polymer composites

Abstract

a b s t r a c tObservations are reported on a polymer composite (polyamide-6 reinforced with short glass fibers) in tensile relaxation tests with various strains, tensile creep tests with various stresses, and cyclic tests with a stress-controlled program (ratcheting with a fixed maximum stress and various minimum stresses). Constitutive equations are developed in cyclic viscoelastoplasticity of polymer composites. Adjustable parameters in the stress-strain relations are found by fitting observations in relaxation tests and cyclic tests (16 cycles of loading-unloading). It is demonstrated that the model correctly predicts experimental data in creep tests and dependencies of maximum and minimum strains per cycle on number of cycles up to fatigue fracture of specimens. The influence of strain rate and minimum stress on number of cycles to failure is studied numerically.

Uniaxial tensile mechanical properties and model parameters determination of ethylene tetrafluoroethylene (ETFE) foils

“…Based on Drozdov's theory [6], the Clausius-Duhem inequality Eq. (10) is satisfied with that: Therefore, the stress-strain relation is obtained as follows.…”

“…Generally, the mechanical properties of ETFE foils are typical for polymers and present non-linearity, large plastic deformations as well as strain rate and temperature dependency [5,6]. A survey of the literature shows that many researchers have paid their attention to investigate the mechanical properties of ETFE foils, such as tensile strength, breaking strain, yield stress and elastic modulus.…”

Effect of crystalline structure on the mechanical response of polypropylene under cyclic deformation

“…Constitutive equations in cyclic viscoelastoplasticity of semicrystalline polymers, under an arbitrary threedimensional deformation with small strains, were developed in [31] . We present a version of these relations for uniaxial tensile cyclic tests with a mixed deformation program, when the entire stress-strain diagram is split into three groups of segments: (i) stretching of a virgin specimen (strain grows from ε = 0 to ε = ε max ); (ii) unloading (strain decreases from ε = ε max to ε = ε min ); and (iii) reloading (strain increases from ε = ε min to ε = ε max ).…”

Viscoplastic Behaviour of Polyamides

“…Their constitutive models for various thermoplastics and elastomers consider the total deformation being composed of a sliding part and an elastic part and the stress-strain relation being governed by a strain-energy density function. The resulting constants and parameters are eventually fitted with the experimental data [14][15][16].…”