Simultaneously enhanced interfacial shear strength and tensile strength of heterocyclic aramid fiber by graphene oxide

Heterocyclic aramid fibers,a typical kind of high-performance fibers,have been widely used in aerospace and protection fields because of their excellent mechanical properties.However,the application of heterocyclic aramid fibers as a reinforcement is hindered by the weak interfacial combination with matrix materials,especially epoxy.Traditional strategies enhancing the interfacial shear strength(IFSS)usually decrease the tensile strength.Therefore,simultaneous enhancement of both mechanical properties remains a challenge.Herein,we report a novel heterocyclic aramid fiber with high interfacial shear strength(49.3 MPa)and tensile strength(6.27 GPa),in which 4,4′-diamino-2′-chlorobenzanilide(DABA-Cl)and a small amount of graphene oxide(GO)are introduced through in-situ polymerization.Hydrogen bonds andπ–πinteraction between GO and polymer chains trigger the enhancement in crystallinity,orientation,and lateral interaction of the fibers,thus improving the tensile strength and interfacial shear strength of the fibers.Moreover,the interfacial interaction between fiber and epoxy is enhanced due to the improvement of the surface polarity of the fibers caused by DABA-Cl.Therefore,a method to improve both tensile strength and interfacial shear strength of heterocyclic aramid fibers was found by introducing GO and DABA-Cl,which may provide guidance for the design and preparation of other high-performance fibers.

Bio-inspired self-folding strategy to break the trade-off between strength and ductility in carbon-nanoarchitected materials

Graphene possesses extraordinary mechanical,electronic,and thermal properties,thus making it one of the most promising building blocks for constructing macroscopic high performance and multifunctional materials.However,the common material strength–ductility paradox also appears in the carbon-nanoarchitected materials and some of the key mechanical performance,for example,the tensile strength of graphene-based materials,are still far lower than that of graphene.Inspired by the exceptional mechanical performance of silk protein benefiting from the conformations of folded structures as well as their transitions,this work proposed a topological strategy to yield graphene-based materials with ultrahigh ductility while maintaining decent tensile strength by self-folding graphene sheets.This drastically improved mechanical performance of graphene-based materials is attributed to the exploitation of shearing,sliding,and unfolding deformation at the self-folded interface.Molecular dynamics simulations show that both modulating self-folded length and engineering interface interaction can effectively control the strength,ductility,and the ductile failure of van der Waals interfaces among the self-folded structures,where interfacial shearing,sliding,and unfolding open channels to dissipate mechanical energy.Based on the insights into the atomic-scale deformation by molecular dynamics simulations,the underlying mechanism of deformation and failure of these materials is finally discussed with a continuum mechanics-based model.Our findings bring perceptive insights into the microstructure design of strong-yet-ductile materials for load-bearing engineering applications.

High-performance phosphorene electromechanical actuators

Phosphorene,a two-dimensional material that can be exfoliated from black phosphorus,exhibits remarkable mechanical,thermal,electronic,and optical properties.In this work,we demonstrate that the unique structure of pristine phosphorene endows this material with exceptional quantum-mechanical performance by using first-principles calculations.

Elasticity-based-exfoliability measure for high-throughput computational exfoliation of two-dimensional materials

Two-dimensional(2D)materials are promising candidates for uses in next-generation electronic and optoelectronic devices.However,only a few high-quality 2D materials have been mechanically exfoliated to date.One of the critical issues is that the exfoliability of 2D materials from their bulk precursors is unknown.To assess the exfoliability of potential 2D materials from their bulk counterparts,we derived an elasticity-based-exfoliability measure based on an exfoliation mechanics model.The proposed measure has a clear physical meaning and is universally applicable to all material systems.We used this measure to calculate the exfoliability of 10,812 crystals having a first-principles calculated elastic tensor.By setting the threshold values for easy and potential exfoliation based on already-exfoliated materials,we predicted 58 easily exfoliable bulk crystals and 90 potentially exfoliable bulk crystals for 2D materials.As evidence,a topology-based algorithm indicates that there is no interlayer bondingtopology for 93%predicted exfoliable bulk crystals,and the analysis on packing ratios shows that 99%predicted exfoliable bulk crystals exhibit a relatively low packing ratio value.Moreover,literature survey shows that 34 predicted exfoliable bulk crystals have been experimentally exfoliated into 2D materials.In addition,the characteristics of these predicted 2D materials were discussed for practical use of such materials.