Impact Compressive Properties of Foamed Film with Closed Cell

Abstract

The compressive properties of foamed polyethylene (PE) film with a closed cell for electronic devices have been investigated. A commercial closed cell foamed PE film with a density of 330 kg/m3 was used. Quasi-static testing was carried out at strain rates of 10−3 to 10−1 s−1. The strain rate of the impact test was approximately 105 s−1 by means of split Hopkinson pressure bar method. Within the set of experiments, the compressive stress increased with the strain rate in both the quasi-static and impact test. In particular, the flow stress increased substantially with the increasing strain rate in the impact deformation. At strains of less than 0.4, the trapped air was locally compressed within the cells, which led to the strain rate dependency of strength in the quasi-static test and the impact test.

Effect of Foam Structure on Impact Compressive Properties in Foamed Polyethylene Film

“…However, in spite of same material and same thickness, the difference of flow stress appears in each specimen. As in our previous study [2][3][4], a plateau deformation was observed immediately after compression without the elastic response in the foamed PE film. However, in the spheral type specimen, elastic response was observed.…”

“…Second, the impact compressive test was performed using the split Hopkinson pressure bar (SHPB) method established by Kolsky [5][6][7] at a strain rate of over 10 3 s −1 . In the previous study [2][3][4], we proposed that the transmitted bar have a smaller cross-sectional area, and a lower elastic modulus indicated the high sensitivity of the load measurements of the specimens. In addition, an attempt was made to obtain high sensitivity measurements of the incident stress wave using an incident bar with a flange [2].…”

“…In the previous study [2][3][4], we proposed that the transmitted bar have a smaller cross-sectional area, and a lower elastic modulus indicated the high sensitivity of the load measurements of the specimens. In addition, an attempt was made to obtain high sensitivity measurements of the incident stress wave using an incident bar with a flange [2]. Figure 1 shows the setup of the SHPB apparatus for the impact compressive test, which consisted of a striker, an incident bar, and transmitted bar [3,4].…”

“…In recent years, foamed polyethylene (PE) film has been developed as a thin sealing material for the miniaturization of precision equipment such as smartphones and tablet personal computers because this material has waterproof and dustproof properties [1][2][3][4]. This sealing material was expected to perform as the shock absorption material.…”

“…However, its mechanical properties and compressive behavior have not been reported. Therefore, the authors have investigated the impact compressive properties of foamed PE film using the split Hopkinson pressure bar method [2] and a drop-weight testing machine [3] that was newly developed machine. Furthermore, to investigate the influence of internal fluid on the compression behavior, we visualized the internal fluid using a Schlieren method [4].…”