Mode II interlaminar fracture behavior of carbon bead‐filled epoxy/glass fiber hybrid composite

To investigate the effect of including carbon beads on the mechanical properties of epoxy resin, the fracture toughness of carbon bead‐filled epoxy was earlier evaluated using a CT (compact tension) specimens and Mode I fracture toughness was observed. Based on those results, in this study, the Mode II interlaminar fracture toughness of carbon bead filled epoxy/glass fiber hybrid composites was evaluated using end notch flexure (ENF) specimens. The hybrid composites showed increased Mode II interlaminar fracture toughness. The optimal bead volume fraction was around 15%.     

Highly Stretchable and Strain-Insensitive Liquid Metal based Elastic Kirigami Electrodes (LM-eKE) (Adv. Funct. Mater. 30/2023)

Kirigami, a traditional paper-cutting art, is a promising method for creating mechanically robust circuitry for unconventional devices capable of extreme stretchability through structural deformation. In this study, this design approach is expanded upon by introducing Liquid Metal based Elastic Kirigami Electrodes (LM-eKE) in which kirigami-patterned soft elastomers are coated with eutectic gallium-indium (EGaIn) alloy. Overcoming the mechanical and electrical limitations of previous efforts with paper-like kirigami, the all soft LM-eKE can be stretched to 820% strain while the electrical resistance only increases by 33%. This is enabled by the fluidic properties of the EGaIn coating, which maintains high electrical conductivity even as the elastic substrate undergoes extreme deformation. Applying the LM-eKE to human knee joints and fingers, the resistance change during physical activities is under 1.7%, thereby allowing for stable electrical operation of wearable health monitoring devices for tracking electroencephalogram (EEG) signals and other physiological activity.     

Unveiling the Superior Optical Properties of Novel Melamine-Based Nonlinear Optical Material with Strong Second-Harmonic Generation and Giant Optical Anisotropy

Two melamine-based metal halides, (C₃N₆H₇)(C₃N₆H₆)HgCl₃ (I) and (C₃N₆H₇)₃HgCl₅ (II), are synthesized by incorporating the heavy d¹⁰ cation, Hg²⁺, and the halide anion, Cl⁻. The noncentrosymmetric structure of I results from two unique attributes: large asymmetric secondary building units produced by direct covalent coordination of melamine to Hg²⁺ and a small dihedral angle between melamine molecules. The former makes inorganic modules locally acentric, while the latter prevents planar organic groups from forming deleterious antiparallel arrangement. The unique coordination in I results in an enlarged band gap of 4.40 eV. Due to the large polarizability of the heavy Hg²⁺ cation and the π-conjugated system of melamine, I exhibits a strong second-harmonic generation efficiency of 5 × KH₂PO₄, larger than any reported melamine-based nonlinear optical materials to date. Density functional theory calculations indicate that I possesses giant optical anisotropy, with a birefringence of 0.246@1064 nm.