CPCs泡沫微结构仿生构筑及其压缩力学性能研究

Biomimetic Construction of CPC Foam Microstructure and Its Compressive Mechanical Properties

CPCs(导电聚合物复合材料)泡沫具有高强度、吸能性、隔热隔音等优异特性,拥有应用于建筑、交通运输、电子产品等领域的巨大潜力.然而,由于CPC加工的复杂性,难以实现微观多孔结构的可控设计,导致多孔结构简单而随机,限制了其进一步的应用.受生物材料凭借排列有序的各向异性微结构来提升力学性能的启发,本文通过双向冷冻铸造工艺构筑高度对齐各向异性多孔仿生微结构CPCs.与传统的单向冷冻相比,双向冷冻铸造技术制备的对齐各向异性多孔微结构CPCs泡沫的压缩弹性模量和峰值应力分别提高了18.7%和25.4%,且在循环压缩过程中产生屈曲及塌陷的几率明显降低,50%应变下循环压缩2000次后仍保持了91.1%的峰值应力和89.6%的应变恢复率.结合有限元压缩模拟,压缩力学性能的主要增强机制有:优化了应力分布,有效避免局部应力集中导致塑性变形;微米级孔壁及其组成的3D结构的高弹性行为赋予了仿生结构较强的回弹能力;高度对齐的各向异性通道提供了足够的变形空间,提高了其变形协调能力,增强了结构加卸载过程中的可逆性.

Conductive polymer composite(CPC) foam exhibits excellent characteristics such as high plasticity,energy absorption,as well as thermal and acoustic insulation,and holds enormous potential for applications in various fields including construction,transportation,electronics,etc.However,the porous structure of CPC foam is usually simple and random,which limits its further application.The complexity of CPC processing makes it challenging to achieve a controlled design of micro-porous structures.Inspired by the idea that biomaterials can enhance their mechanical properties by virtue of their well-aligned anisotropic microstructures,highly aligned anisotropic porous biomimetic microstructures are constructed by a bidirectional freeze-casting process to enhance the compressive mechanical properties of CPC foam.Compared to traditional unidirectional freezing,the compressive elastic modulus and peak stress of aligned anisotropic porous microstructured CPC foam increase by 18.7% and 25.4%,respectively.Buckling and collapsing risks during cyclic compression are significantly reduced,and a peak stress of 91.1% and a strain recovery of 89.6% are still maintained after 2,000 cycles at 50% strain.A finite element model of the porous structure in CPC foam is built with parameters including elastic modulus,hole wall thickness,and Poisson's ratio,obtained from measured data or literature.The quasi-static compressive behaviors of biomimetic and disordered structures are investigated using the finite element method,and the deformation and stress distribution are compared with the corresponding experimental results.Through finite element simulations and experimental tests,it is found that the main mechanisms enhancing the compressive mechanical properties of the materials are as follows:stress distribution optimization effectively prevents plastic deformation caused by local stress concentration;the highly elastic behavior of micrometer pore wall and its 3D structure enhance the bionic structure's resilience;and the highly aligned anisotropic channels provide ample deformation space,improve deformation coordination,and enhance the structure's reversibility during loading and unloading.