Abstract
Polymeric systems have wide applications in engineering domains such as aerospace, automobile, biomedical, sports goods, packaging, electronics and optics, and energy sectors. These materials exhibit hyperelastic and time-dependent responses such as relaxation and strain-rate-dependent elasticity. Finite element analysis of polymeric components requires material properties for different constitutive models that are obtained from experimental results at the coupon level. Molecular dynamics (MD) simulations can be used to simulate these responses, however, the time and length gap is a challenge to overcome. MD simulations are conducted for a very short time, e.g. nanoseconds to femtoseconds which overestimates the mechanical properties. This study develops a bridging technique for time and predicts stress-stress strain response for cyclic loading at experimental frequency using MD simulations results conducted at high frequency. Molecular models are deformed under cyclic loadings at three different frequencies. Four different strain amplitudes are applied at one frequency. A dimensionless time parameter is introduced and the profile for stress amplitudes transformation to experimental level is predicted. Assuming an underdamped system, the decaying of stress amplitude over time and phase difference is calculated. Experiments are conducted for cyclic loadings of up to three different loads. The prediction agrees well with the experimental results.
