Search

Biological strong and tough materials have been providing original structural designs for developing bioinspired high‐performance composites. However, new synergistic strengthening and toughening mechanisms from bioinspired structures remain yet to be explored and employed to upgrade current carbon material reinforced polymer composites, which are keystone to various modern industries. In this work, from bamboo, the featured cell face‐bridging fibers, are abstracted and embedded in a cellular network structure, and develop an epoxy resin/carbon composite featuring biomimetic architecture through a fabrication approach integrating freeze casting, carbonization, and resin infusion with carbon fibers (CFs) and carbon nanotubes (CNTs). Results show that this bamboo‐inspired crack‐face bridging fiber reinforced composite simultaneously possesses a high strength (430.8 MPa) and an impressive toughness (8.3 MPa m1/2), which surpass those of most resin‐based nanocomposites reported in the literature. Experiments and multiscale simulation models reveal novel synergistic strengthening and toughening mechanisms arising from the 2D faces that bridge the CFs: sustaining and transferring loads to enhance the overall load‐bearing ability and furthermore, incorporating CNTs pullout that resembles the intrinsic toughening at the molecular to nanoscale and strain delocalization, crack branching, and crack deflection as the extrinsic toughening at the microscale. These constitute a new effective and efficient strategy to develop simultaneously strong and tough composites through abstracting and implenting novel bioinspired structures, which contributes to addressing the long‐standingly challenging attainment of both high strength and toughness for advanced structural materials. [ABSTRACT FROM AUTHOR]

High strength concrete (HSC) with superior strength advantage has been gaining widespread attention and engineering endorsement in recent years. For a better understanding of the mechanical responses and failure mechanisms of HSC, a novel three‐dimensional (3D) mesoscale model considering the meso‐structural features of concrete was proposed in this paper. First, a series of uniaxial compressive tests were conducted to investigate the compressive properties of HSC specimens with a strength of 80–90 MPa. After that, a 3D three‐phase mesoscale model consisting of mortar, coarse aggregate, and the interfacial transitional zone (ITZ) between them, was developed to perform the mesoscopic simulations of HSC. Then, systematic analysis and discussions on the compressive properties of HSC were presented in terms of the stress–strain curves, compressive strengths/toughness, failure patterns, cracking process, etc. Results indicate that HSC exhibited obvious brittle failure characteristics, and its strength was significantly related to the water‐to‐cement ratio and mineral admixture. At meso‐level, the cracking behaviors of mortar and ITZ phases were well modeled using the developed mesoscale model. Additionally, it was found that the cracking behavior of HSC was significantly associated with the ITZ characteristics. The developed mesoscale modeling approach has been proven to simulate and investigate concrete's compressive properties in a reliable manner, and can be applied further to the property analysis of concrete materials and structures. [ABSTRACT FROM AUTHOR]

Split Hopkinson pressure bar (SHPB) with 75-mm diameter is used to conduct dynamic impact compression tests on different strength grades of basic magnesium sulfate cement-coral aggregate concrete (BMSC-CAC). The failure process of BMSC-CAC under dynamic impact compression is simulated using the finite element software LS-DYNA and a three-dimensional random aggregate mesoscopic model. The results show that BMSC-CAC has a significant strain rate effect, and the dynamic impact strength increases as the strain rate increases. Because of the high toughness of BMSC, BMSC-CAC has higher energy absorption than coral aggregate seawater concrete (CASC) and sisal fiber coral aggregate seawater concrete (SFCASC). The LS-DYNA software is used for the numerical simulation of the mesoscale dynamic impact compression. The relative error of the peak stress and strain between the test and simulation results is small. Analysis of the failure process indicates that the damage extent of the aggregate increases, and the failure time decreases with an increase in the strain rate. [ABSTRACT FROM AUTHOR]