Effect of strain rate and load orientation on cyclic response of anisotropic polyurethane foam

Abstract

Anisotropic cellular materials, such as polymeric foams, play an important role in structures subjected to cyclic loadings. The present paper provides an experimental investigation of the mechanical behavior of an anisotropic polyurethane foam subjected to cyclic compressive loadings under two perpendicular orientations: the rising and perpendicular directions. The foam samples are loaded under three different strain rates and various deformations. The experimental results are presented in terms of elasticity modulus, maximal compressive stress, effective energy absorption capacity, and residual strain. It is proved that the investigated polyurethane foam presents a macroscopic mechanical anisotropy caused by microscopic cell elongation in the foaming direction. Moreover, it is demonstrated that the mechanical behavior of the foam is fully influenced by both deformation rates and imposed strains. The experimental stress–strain curves are modelized using an empirical model considering an adjustable modulus of elasticity. The analytical results show a good agreement with the experiments.

Soft polyurethane foam reinforced by expanded polystyrene particles: Compression performance, strain rate, and cyclic compression response

“…The compression performance is highly dependent on the strain rate and the strain rate of all samples is in direct proportion to the loading rate. This phenomenon suggests that the materials have a strong viscoelastic nature 5 and polymeric materials demonstrate interlocked chains that increase with the strain rate, which means the stress increases concurrently 28 . Figure 10C shows that with a strain rate increasing from 1 to 300 mm/min gradually and a specified 75% strain, the pure PU foam demonstrates stress that is improved from 0.058 to 0.09 MPa.…”

“…This phenomenon suggests that the materials have a strong viscoelastic nature 5 and polymeric materials demonstrate interlocked chains that increase with the strain rate, which means the stress increases concurrently. 28 Figure 10C shows that with a strain rate increasing from 1 to 300 mm/min gradually and a specified 75% strain, the pure PU foam demonstrates stress that is improved from 0.058 to 0.09 MPa. However, with more content of EPS particles being incorporated, the loading rate exerts a continuously mitigated effect over the strain rate.…”