Impact resistance is vital for marine and protective structural composites. Conventional glass fiber/epoxy thermosets feature high specific strength but suffer poor recyclability. Herein, recyclable triaxial glass fiber-reinforced PMMA (Triax-GF/PMMA) laminates were manufactured, and quasi-static tensile, compressive and shear tests were conducted to obtain the fundamental mechanical constitutive parameters for the subsequent impact performance analysis. Low-velocity drop-weight impact (15-120 J) and compression-after-impact (CAI) experiments were carried out. Under a 50 J impact condition, the residual compressive strength of Triax-GF/PMMA reached 131.5 MPa, which was approximately 9.8% higher than that of the epoxy counterpart (119.8 MPa). Meanwhile, the peak impact load of Triax-GF/PMMA increased to 11.84 kN, compared with 9.98 kN for the epoxy system, indicating enhanced impact load-bearing capability. An ABAQUS/Explicit finite element model with Hashin failure criteria was validated by experimental results, with the relative errors of predicted peak loads maintained below 8%. Simulations at 30 J (non-penetration) and 120 J (penetration) showed milder deformation and slighter damage in Triax-GF/PMMA. A predictive model linking laminate thickness and perforation energy was further proposed. This work provides experimental and numerical support for the development of lightweight, recyclable, impact-resistant composites for potential marine applications.
To address the clogging issue commonly encountered with rapid-setting and hardening concrete, a liquid-solid separation 3D printing nozzle was proposed based on coupled EDEM-Fluent simulations, and its printing performance was verified. First, finite element models of different nozzle types were established, and Fluent simulations were conducted to analyze the slurry flow velocity and turbulence intensity inside the nozzle, from which the optimal outlet shape was determined. Next, the mixing effectiveness of stirring blades with various structural configurations was evaluated using EDEM, and the optimum combination of blade inclination angle, blade number, and stirring speed was identified through orthogonal experiments. Finally, the liquid-solid separation nozzle was designed, and its printing performance was experimentally validated. The results show that the conical nozzle achieves an outlet velocity standard deviation of 0.0144, indicating favorable velocity uniformity. Using the coefficient of variation as the evaluation index, the lowest value is obtained at a blade inclination angle of 40 degrees, with three blades and a stirring speed of 120 rpm, representing the best mixing performance. In a 1 h continuous printing test, the newly developed nozzle operated without clogging, demonstrating the feasibility of the proposed design for short-duration printing tasks. Moreover, the compressive strength of the printed rapid-setting and hardening specimen (A2) was 14.3% higher than that of the conventionally cast specimen (A1), whereas the flexural strength did not exhibit a significant advantage.
TiC-based cermets are promising candidates for marine wear-resistant components; however, achieving a balance between mechanical performance, erosion-corrosion resistance, and binder cost remains a major challenge. In this work, TiC-xFe-(15-x)Ni (x = 0, 5, 10 and 15 wt.%) cermets were fabricated by vacuum liquid-phase sintering to clarify the influence of Fe/Ni binder composition on the microstructure, mechanical properties, electrochemical behavior, and erosion-corrosion resistance in SiO2-containing artificial seawater. The results indicate that the Fe content has a significant impact on liquid-phase sintering behavior, thereby affecting the densification of cemented carbides. The combination of TiC-5Fe-10Ni achieved the highest relative density (98.89%), Vickers hardness (1618 HV), and fracture toughness (10.26 MPa & centerdot;m1/2), while also exhibiting the lowest corrosion current density in electrochemical corrosion tests. In contrast, TiC-10Fe-5Ni cemented carbide showed the lowest cumulative mass loss in long-term erosion-corrosion tests. Conversely, excessive Fe addition leads to suboptimal performance. The performance improvement is mainly attributed to densification and reduced residual porosity achieved through the optimization of liquid-phase sintering, which provides an effective strategy for designing cost-effective TiC-based composites with balanced mechanical properties and long-term corrosion and erosion resistance.
The development of renewable polymer networks combining mechanical performance with repairability and reprocessability is important for advancing sustainable materials. In this study, chitosan-dialdehyde lignin (Ch-DAL) bioplastic films were fabricated through dynamic Schiff base cross-linking between tartaric acid-protonated chitosan and periodate-oxidized lignin, with glycerol as a plasticizer. Films with Ch:DAL ratios of 1:1, 2:1, and 1:2 were characterized by Fourier-transform infrared (FTIR) spectroscopy, tensile testing, qualitative solvent-resistance assessment, a thermally assisted repair test, and two successive thermo-mechanical reprocessing cycles. FTIR analysis was consistent with the possible formation of imine (C=N) linkages and the contribution of hydrogen-bonding interactions, although aldehyde content, degree of conversion, and cross-link density were not quantitatively determined. The mechanical properties were composition-dependent, with the 1:1 formulation exhibiting the highest tensile strength (8.85 +/- 0.09 MPa) and Young's modulus (118.7 +/- 0.7 MPa), whereas the 2:1 formulation exhibited the highest elongation at break (238 +/- 0.1%). Thermogravimetric analysis (TGA) and derivative thermogravimetry (DTG) showed distinct thermal-degradation profiles for alkali lignin, DAL, and the 1:1 Ch-DAL film, with residual masses of approximately 17%, 57%, and 33% at 600 degrees C, respectively. Qualitative assessment showed that the films retained structural integrity in water, 1 M sodium hydroxide (NaOH), and the investigated organic solvents but underwent visible fragmentation in 1 M hydrochloric acid (HCl). Following hot pressing of the cut 1:1 film at 50 degrees C, macroscopic continuity was re-established and tensile strength increased to 12.9 +/- 0.11 MPa; however, elongation at break decreased from 19.0 +/- 0.1% to 4.3 +/- 0.05%, indicating a mechanically distinct repaired state rather than recovery of the original properties. Fragmented films could also be remolded through two successive thermo-mechanical reprocessing cycles, although tensile strength decreased substantially after the first cycle and recovered only partially during the second cycle. These findings demonstrate composition-dependent mechanical behavior, thermally assisted repair, and remolding capability in Ch-DAL films, while further quantitative characterization, durability testing, and environmental assessment are required before claims regarding long-term performance or sustainability can be established.
Poly(epsilon-caprolactone)-based segmented polyurethanes (PUs) were developed as potential materials for bone tissue engineering, with particular emphasis on porous substitutes for cancellous bone. PUs with hard segment (HS) contents ranging from 17.6 to 32.0% were synthesized from poly(epsilon-caprolactone) diol, 1,6-hexamethylene diisocyanate, and 1,4-butanediol. The effects of HS content and post-synthesis incubation temperature (40 and 80 degrees C) on the structural, thermal, surface, mechanical, and biological properties were investigated. The polyurethane containing 25.5% HS exhibited a favorable combination of structural and mechanical properties and was selected for the preparation of porous composites containing microhydroxyapatite (mu HAp) and ZrO2. The resulting composites exhibited high open porosity (70.4-73.3%). The physicochemical characteristics of mu HAp support its proposed role as a predominant water-carrying ceramic phase promoting in situ CO2 generation during polyurethane crosslinking; however, because mu HAp and ZrO2 were incorporated simultaneously, their individual contributions to foaming cannot be unequivocally distinguished. Extract-based MTT testing showed no cytotoxic effects under the investigated conditions. Furthermore, the 30-day stability assessment at 37 degrees C revealed low mass loss, preservation of Young's modulus, and only minor changes in molecular weight parameters, supporting the short-term stability of the investigated materials. Overall, the results support further development of these porous PU/ceramic composites as materials for bone tissue engineering.
