Porous materials with engineered stretching-dominated lattice designs, which offer attractive mechanical properties with ultra-light weight and large surface area for wide-ranging applications, have recently achieved near-ideal linear scaling between stiffness and density. Here, rather than optimizing the microlattice topology, we explore a different approach to strengthen low-density structural materials by designing tube-in-tube beam structures. We develop a process to transform fully dense, three-dimensional printed polymeric beams into graphitic carbon hollow tube-in-tube sandwich morphologies, where, similar to grass stems, the inner and outer tubes are connected through a network of struts. Compression tests and computational modelling show that this change in beam morphology dramatically slows down the decrease in stiffness with decreasing density. In situ pillar compression experiments further demonstrate large deformation recovery after 30–50% compression and high specific damping merit index. Our strutted tube-in-tube design opens up the space and realizes highly desirable high modulus–low density and high modulus–high damping material structures.

具有工程拉伸主导晶格设计的多孔材料具有吸引人的机械性能，具有超轻重量和大表面积，适用于广泛的应用，最近在刚度和密度之间实现了近乎理想的线性比例。在这里，我们不是优化微晶格拓扑结构，而是通过设计管中管梁结构来探索一种不同的方法来增强低密度结构材料。我们开发了一种工艺，可将完全致密的三维打印聚合物梁转化为石墨碳中空管中管三明治形态，其中，类似于草茎，内管和外管通过支柱网络连接。压缩测试和计算模型表明，梁形态的这种变化显着减缓了刚度随密度降低而降低的速度。原位柱压缩实验进一步证明了 30-50% 压缩后的大变形恢复和高比阻尼优点指数。我们的支撑管中管设计打开了空间，实现了非常理想的高模量-低密度和高模量-高阻尼材料结构。