ABSTRACT
Auxetic re-entrant honeycomb (AREH) structures, consisting of a single soft or tough material, have long faced the challenge of balancing stiffness and rebound resilience. To achieve this balance, dual-material printing technology is employed to enhance shock absorption by combining layers of soft and tough materials. Additionally, a novel structure called the curved re-entrant honeycomb (CREH) structure has been introduced to improve stiffness. The selected materials for processing the composite structures of AREH and CREH are the rigid thermoplastic polymer polylactic acid (PLA) and the soft rubber material thermoplastic polyurethane (TPU), created utilizing fused deposition modeling (FDM) 3D printing technology. The influence of the material system and structure type on stress distribution and mechanical response was subsequently investigated. The results revealed that the dual-material printed structures demonstrated later entry into the densification phase compared to the single-material printed structures. Moreover, the soft material in the interlayer offered exceptional protection, thereby ensuring the overall integrity of the structure. These findings effectively serve as a reference for the design of dual-material re-entrant honeycombs.
ABSTRACT
As an effective technique for fabricating conductive and thermally conductive polymer composites, a multi-filler system incorporates different types and sizes of multiple fillers to form interconnected networks with improved electrical, thermal, and processing properties. In this study, DIW forming of bifunctional composites was achieved by controlling the temperature of the printing platform. The study was based on enhancing the thermal and electrical transport properties of hybrid ternary polymer nanocomposites with multi-walled carbon nanotubes (MWCNTs) and graphene nanoplates (GNPs). With thermoplastic polyurethane (TPU) used as the matrix, the addition of MWCNTs, GNPs and both mixtures further improved the thermal conductivity of the elastomers. By adjusting the weight fraction of the functional fillers (MWCNTs and GNPs), the thermal and electrical properties were gradually explored. Here, the thermal conductivity of the polymer composites increased nearly sevenfold (from 0.36 W·m-1·k-1 to 2.87 W·m-1·k-1) and the electrical conductivity increased up to 5.49 × 10-2 S·m-1. It is expected to be used in the field of electronic packaging and environmental thermal dissipation, especially for modern electronic industrial equipment.
