Lijun Ji

Monolithic multi-layer V-corrugated sandwich panels with two distinct stacking configurations (overlapping and interlacing laminations) were additively fabricated via fused deposition modeling (FDM) using polylactic acid (PLA) filaments. Quasi-static flatwise compression testing demonstrates that interlacing laminates exhibit 50% greater flatwise compressive strength than their overlapping counterparts. Combined mechanical characterization and force transmission analysis demonstrate divergent failure mechanisms between the two configurations: interlacing laminates undergo core-dominated crushing failure, as their vertical load-bearing vertices are perfectly aligned; by contrast, overlapping laminates undergo face-sheet bending failure owing to staggered load-bearing points. During flatwise compression, interlacing structures exhibit progressive layer-by-layer collapse, which endows them with superior damage tolerance and energy absorption capability. In contrast, overlapping structures suffer sudden global catastrophic failure upon reaching the critical load threshold. A parametric tuning strategy targeting core wall thickness and interlayer sheet thickness is proposed to enhance the flatwise compressive strength of corrugated sandwich panels, and the underlying failure mechanisms are systematically validated. Benefiting from the core-crushing-dominated failure mode, interlacing laminates also deliver enhanced edgewise and sidewise compressive performance compared with overlapping designs. Nevertheless, the ultimate load-bearing capacity of both lamination designs is governed by the total number of stacked layers, whereas their compressive strength is primarily dictated by stacking geometry. This study clarifies how lamination stacking configurations modulate the triaxial compressive responses of microscale FDM-printed sandwich structures and delivers design guidelines for lightweight, high-performance 3D-printed sandwich panels.

Conventional ultraviolet (UV) absorbers used to enhance the anti‐UV performance of medical materials are often toxic and potentially harmful to humans. Therefore, developing a safe alternative to protect against UV radiation is of great importance. In this research, a transparent material was prepared by copolymerizing methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA), and methacryloxy‐terminated PDMS (M‐PDMS). Compared to a PDMS‐MMA copolymer, the cut‐off wavelength of the PDMS‐HEMA‐MMA copolymers extended from 325 to 355 nm without the use of any UV absorbers, while the transmittance in the range of 355–800 nm could be adjusted by regulating HEMA content. SAXD and atomic force microscope (AFM) characterization confirmed that the copolymers underwent phase separation after the addition of HEMA, resulting in an increase in light scattering. Besides, increasing the HEMA content enhanced the hydrophilicity of the PDMS‐HEMA‐MMA copolymers and reduced the protein adsorption amounts by 39.0%. Fourier transform infrared spectra (FTIR) analysis revealed that hydrogen bonds formed between the ‐OH groups in HEMA and other macromolecules, which significantly enhanced the thermal stability and T _g of the copolymer. The addition of HEMA also decreased the rigidity and increased the elasticity of the copolymers. This PDMS‐HEMA‐MMA copolymer with anti‐fouling and UV‐visible shielding properties is promising for application in ophthalmology.

Methyl methacrylate (MMA) was copolymerized with a methacryloxy‐ terminated poly(dimethylsiloxane) macromer (M‐PDMS) in order to improve the mechanical properties. The results of dynamic mechanical analysis, differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy, small‐angle X‐ray scattering and atomic force microscopy confirmed that the monomer concentrations and reactivity ratios affected the polymerization kinetics, resulting in the formation of two different macromolecules at the beginning and end of the polymerization. With the addition of M‐PDMS, the phase separation of the MMA‐PDMS copolymers (M‐PDMS_X, X represents the mass fraction of M‐PDMS in the copolymers) became more pronounced, but the difference in molecular structure between the continuous phase and the dispersed phase became smaller, which led to higher light transmittance, hydrophobicity and thermal stability. Tensile tests confirmed that the tensile strength and tensile modulus of M‐PDMS_20 (33.10 MPa and 1.35 GPa) was 55 times and 229% those of PMMA (0.6 MPa and 0.59 GPa). An in vitro cytotoxicity test confirmed the MMA‐PDMS copolymer was biocompatible. This research revealed the formation mechanism of the microstructure of the MMA‐PDMS copolymer, and provided valuable guidance for the design and synthesis of this material.

C/Ti ₃ C ₂ /g-C ₃ N ₄ Schottky junction hollow microspheres were prepared by the template method.

Micron-scale grid-shaped, V-shaped and U-shaped corrugated sandwich structures are fabricated by 3D printing technology and present different mechanical properties from those made by traditional method. Their peak stresses and elastic moduli could be fitted to cubic functions. The compression performance of the multilayer grid-shaped sandwich can be determined by the relative mechanical strength of layers. Adding a layer on a grid-shaped sandwich has no significant influence on the peak stress, but can enhance the elastic modulus by about 60.9 MPa. The deformation modes of multilayer V-shaped and U-shaped sandwiches can be determined by the load carrying path and the relative mechanical properties between interlayers and cores. The elastic modulus of V-shaped sandwich is enhanced with the increase of layer number, while the elastic modulus of U-shaped sandwich decreases with the increase of layer number. The peak stress and the elastic modulus of a four-layer V-shaped sandwich can reach 9.85 MPa and 261.09 MPa, and those of a four-layer U-shaped sandwich can reach 4.79 MPa and 119.18 MPa. The result reveals the principles that the reduced structural size and suppressed debonding, the structures and the load carrying path, and materials, influence the failure mode and mechanical properties of the corrugated sandwiches.