Abstract
As a kind of metamaterial, the negative Poisson’s ratio foams, which expand (shrink) in the transverse direction when stretched (compressed) in the longitudinal direction, have many potential applications in fields such as aerospace and mechanical and biomedical engineering. In this paper, the out-of-plane crushing behaviors of four types of the orthogonal isotropic NPR convex-concave foams (CCF) were extensively studied using an electronic universal testing machine and Instron machine at different strain rates where each test was conducted at a constant compressive velocity under uniaxial compression. Strain rate effect on mechanical properties of these foams is experimentally studied. When the strain rate increases, the compressive force enhancement of the foams is obvious and varies with different specimens. The difference in energy absorption and deformation patterns for these foams between quasi-static and dynamic loading conditions is also analyzed. We find that the deformation patterns for the specimens are not only related to the compressive velocities but also the topologies of the specimens. The research in this paper is expected to be meaningful for the optimization design of the foam structures/materials widely used in the fields of aerospace and mechanical and biomedical engineering.
Highlights
Negative Poisson’s ratio (NPR) foams, which expand in the transverse direction when stretched in the longitudinal direction, are a typical kind of mechanical metamaterial (Yang et al, 2004)
The concave foams (CCF) are constructed by replacing cell edges of the conventional open cell foams (COF), whose straight cell edges of square cross sections are arranged in planes at forty-five degrees relative to each other (Dolla, 2014), with sin-shaped cell edges of equal mass but different cross sections
Four groups of foam specimens, namely COF0, CCF1, CCF2, CCF3, with different h/l0 ratios were tested at 5 m/s, 15 m/s, and 2 mm/min, for which the corresponding strain rates are 71.4, 2.14 × 102, and 4.76 × 10−2s−1
Summary
Negative Poisson’s ratio (NPR) foams, which expand (shrink) in the transverse direction when stretched (compressed) in the longitudinal direction, are a typical kind of mechanical metamaterial (Yang et al, 2004). Dou et al (2016) investigated the influence of strain rate on the aluminum foam sandwich panels based on the finite element models Taking into account their special properties originating from the effect of NPR, a variety of NPR foams have been proposed for applications in the medical fields. Within the auxetic scaffold under mechanical (compression) stimulation was studied Dedicated to promoting their applications in the fields of vehicle, mechanical, aerospace, and medical engineering, in this paper, strain rate effects on mechanical behaviors of the NPR CCF are further systematically studied. Choosing one conventional foam (COF) and three NPR convex-concave foams (CCF) of equal mass as examples for illustration, strain rate effects on forcedisplacement curves and energy absorption, the damage patterns of the NPR CCF, and the influence of geometrical morphology on the mechanical properties of NPR foams are experimentally investigated. The data of compressive force has a slight gap, the overall trend is basically the same and there is good repeatability
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