To improve the plastic instability of a thermoplastic polymer composite under cold forming, a copper mesh was filled into the polypropylene (PP). PP-Cu mesh composite plate specimens with the Cu mesh inclined in various directions were formed by the compression molding of the PP pellet and Cu mesh. First, the tensile behavior of Cu meshes with the angles of 0/90°, 15/75°, 30/60° and 45° to the tensile direction was examined. The maximum stress decreased gradually with increasing Cu mesh angle to the tensile direction because the Cu wires rotated in the tensile direction. The anisotropic response was also confirmed for the PP-Cu mesh composite, and the anisotropy was emphasized for composites with the higher volume fractions of the Cu mesh. The decrease in the nominal stress, which is often seen in the tensile deformation of the thermoplastic polymer, almost disappeared for the composite specimen with the Cu mesh at the angle of 45° to the tensile direction. Also, the deformation concentration in the specimen was effectively suppressed by reducing the deformation resistance in the early stage of deformation and by increasing the strain hardening after yielding.
Mechanical experiments have been performed to investigate the dynamic creasing characteristics of coated paperboard mainly used in the food packaging industry. The correlation between the time-dependent relaxation of bending resistance at a specified folded position and the dynamic release behavior of creased paperboard was experimentally investigated for a time period of 0.1-1000s. The transition of in-plane tensile stress relaxation and that of bending moment relaxation were detected in the time period of 10-30s in a specified paperboard, when using a constant deformation rate for creating the initially loaded state. We varied the stopping time of the folded state of a creased part, and analyzed the time-dependent released behavior (unfolded deformation) using the improved relaxation model, which is based on the power rule of relaxation time. The results obtained with this model show a good fit to the experimental results, and the proposed release time of the unfolding process is found to be almost independent of the stopping time.
A method for synthesizing a unidirectional porous （UniPore） aluminum structure employing a cylindrical explosive compaction assembly is proposed and the condition for successful recovery is discussed. The microstructure of the compacted samples is demonstrated to show tight bonding between the walls with uniform pores oriented in one direction. The compacting process is numerically simulated by the Autodyn code and the results are similar to the experimental results. The results of compression tests showing a plateau region are also demonstrated.