Materials & Design最新文献

The fracture toughness of oxide glasses can be improved through controlled crystallization, forming glass-ceramics. However, to fully exploit their potential, an atomic-scale understanding of the toughening mechanism is needed. In this work, we investigate the structural origin of the variation in fracture toughness of barium titanosilicate glass-ceramics with varying crystallinity by combining experiments and molecular dynamics simulations. Generally, the glass-ceramics exhibit improved hardness, elastic modulus, and fracture toughness compared to the precursor glasses. The simulation results of 40BaO-20TiO₂-40SiO₂ glass-ceramics reveal that the differences can primarily be attributed to titanium bond switching events, namely, the change of the titanium coordination number under stress to dissipate mechanical energy. We also show that by tuning the content and aspect ratio of the formed fresnoite crystals, the fracture behavior of the glass-ceramics can be modified due to the redistribution of the stress field before fracture, which in turn controls the fracture path.

Sulfur mustard (2,2′-dichloroethylsulfide; SM) is a bifunctional alkylating agent that can easily penetrate skin and cause persistent pain and damage. Effective biological dressings are required to treat wounds caused or poisoned by SM. Though the use of SM is regulated under the Chemical Weapons Convention, it is still a threat during wars and terrorist attacks. Herein, we present a photothermal-enhanced detoxification microneedles array (MNA) encapsulated with ZnIn₂S₄@UiO-66-NH₂ (ZnInS/UIO) catalysts for the treatment of 2-chloroethyl ethyl sulfide (CEES, SM analog)-poisoned wounds under simulated sunlight (SSL) irradiation. Due to the excellent photothermal detoxification capability possessed by ZnInS/UIO, the conversion rate of CEES can be significantly increased under SSL exposure. When encased in a polyvinyl alcohol (PVA) MNA and piercing into the skin, ZnInS/UIO catalysts can be released quickly from MNA for detoxification. After applying the resultant ZnInS/UIO-MNA to the CEES-poisoned wound bed, acceleration of the wound healing process and a reduced inflammatory response can be confirmed. In conclusion, ZnInS/UIO-MNA has encouraging potential as a first-aid dressing for CEES-poisoned wound healing in battlefields and injuries related to acts of terrorism.

Constructing lunar bases is crucial as lunar missions progress towards utilization and exploitation. The challenging lunar environment, with its unique characteristics and limited resources, requires special materials, structures, and construction methods. Inflatable structures offer great potential for lunar construction due to their advantages in transportation, stowage, construction, and reliability. This paper proposes a rigidizable inflatable lunar habitat that maintains its shape even after air leakage, enhancing safety, durability, and fixability. The membrane material adapts to different requirements during transportation, construction, and service, achieved through solid-state actuation of shape memory polymer (SMP) for stiffness variation, allowing multiple moves and ground tests. This work comprises three parts: 1) system: design concept and construction processes, 2) material: design and characterization of restraint and rigidization materials, and 3) structure: numerical validation of structure properties. Finite element analysis, based on material models obtained through dynamic mechanical analysis (DMA) and tensile tests, demonstrates the effectiveness of including an SMP rigidization layer in preventing collapse and enhancing dynamic properties. This paper not only proposes a new system, but also provides material design methods and requirements, along with structural validation techniques. Findings validate the feasibility of rigidizable inflatable lunar habitats, applicable in extreme environments, also in temporary buildings, space structures, and soft robotics.

This work concerns the laser wire directed energy deposition (LW-DED) additive manufacturing process. The objectives were two-fold: (1) process mapping – demarcating the process states as a function of the processing parameters; and (2) process monitoring – detecting process anomalies (instabilities) using data acquired from an in-situ meltpool imaging sensor. The LW-DED process enables high-throughput, near-net shape manufacturing. Without rigorous parameter control, however, LW-DED often introduces defects due to stochastic process drifts. To enhance scalability and reliability, it is essential to understand how LW-DED parameters affect processing regimes, and detect deleterious process drifts. In this work, single-track experiments were conducted over 128 combinations of laser power, scanning velocity, and linear mass density. Four process states were observed via high-speed imaging and delineated as stable, dripping, stubbing, and incomplete melting regimes. Physically intuitive meltpool features were used to train simple machine learning models for classifying the process state into one of the four regimes. The approach was benchmarked against computationally intense, black-box deep machine learning models that directly use as-received meltpool images. Using only six intuitive meltpool morphology and intensity signatures, the approach classified the LW-DED process state with statistical fidelity approaching 90 % (F1-score) compared to F1-score 87 % for deep learning models.

In the dynamic interaction between the runner and the ground, the running shoe is the only medium that bears the impact force of body weight and plays a crucial role in athletic performance. Traditional designs do not adequately consider the different shapes of the foot, which often leads to discomfort and aggravation of foot disorders. This study presents an innovative approach to running shoe midsole design using 3D-printed chiral negative poisson’s ratio (NPR) structures to enhance shock absorption and support, thereby optimizing biomechanical performance and comfort. Using computer-aided design (CAD) and computer-aided engineering (CAE), the biomechanical effects of different midsole structures has been explored through finite element analysis (FEA). The study focuses on optimizing the cushioning, propulsion and stability of the midsole to mitigate the impact on the ankle and knee. Static compression and dynamic impact simulations were utilized to comprehensively select optimized design of midsole structure and the selected structures was 3D printed to validate the biomechanical benefits in a wear trial. The results of the study highlight the superior performance of chiral NPR structures in reducing forefoot stress during standing and movement and advance the design and functionality of 3D printed materials in running shoes.

Step adhesive joints have a special characteristic quite different from other joints. When initial delamination occurs in other joints such as butt, lap and scarf joints, final failure always occurs. In these cases, the external stress causing initial delamination ${\sigma }_c^{\mathrm{Initial}}$ is equal to the final failure stress as ${\sigma }_c^{\mathrm{Final}}$ = ${\sigma }_c^{\mathrm{Initial}}$. However, in step joints, the final failure stress ${\sigma }_c^{\mathrm{Final}}$ can be greater than the initial delamination stress ${\sigma }_c^{\mathrm{Initial}}$ < ${\sigma }_c^{\mathrm{Final}}$. To clarify the adhesive improvement mechanism, first, this paper discusses the ISSF (Intensity of Singular Stress Fields) for fully bonded step joint by varying the number of steps $N_S$. Second, the singular stress field causing 2nd debonding is discussed by analyzing partially delaminated step joint. The results show that 2nd debonding requires larger external load than the initial debonding as ${\sigma }_c^{\mathrm{Initial}}$ < ${\sigma }_c^{\mathrm{Final}}$. This is because under the same external load the singular stress causing the 2nd deboning is smaller than the one causing the initial debonding. When $N_S\ge 6$ and suitable overlap length, the final bond strength ${\sigma }_c^{\mathrm{Final}}$ can be more than 3.6 ∼ 4.4 times larger than the initial delamination stress ${\sigma }_c^{\mathrm{Initial}}$ $\ll {\sigma }_c^{\mathrm{Final}}$ resulting in much larger bond strength.

Frequency selective surfaces (FSSs) are significant for the efficient and accurate transmission of microwave signals due to its ability to selectively shield electromagnetic (EM) waves of different frequencies. In some special scenarios, mechanical properties are vitally required. Herein, a flexible frequency selective fabric (FSF) is proposed. Different from traditional FSSs or reported FSFs, aramid/carbon fiber woven fabric serve as the flexible substrate in which carbon fiber provides functionality instead of metallic materials, and patches made of carbon fiber prepreg are periodically applied for property reinforcement. Equivalent circuit model is used to guide the basic determination of patch’s geometry, and it is further optimized via full-wave simulation software HFSS. A simulation model that reasonably reflect the correlation between structure and frequency-selection characteristic is provided, and structural factors affecting the characteristic are analyzed and discussed. Further, an FSF sample is prepared and its frequency response is measured. Measurement revealed the FSF selectively shields EM waves in the frequency range of 8.9 GHz to 11.4 GHz, and is of the bandpass-bandstop-bandpass characteristic. Benefit from EM property and flexibility, the proposed FSF has advantages in applications pursue lightweight, high strength, and require excellent EM functionality, such as aerospace and structure-EM function integrated products.

Infection and poor osteogenesis are two major causes of implant failure. Surface modification strategy provides solutions to the above problems. However, the functional requirements at different biological stages during infectious bone repair and the oxidative stimulation caused by reactive oxygen species (ROS) in an inflammatory environment pose challenges to the existing approaches. Layer-by-layer (LbL) self-assembly realizes layer by layer superposition and time-dependent acting of different bioactive components, but is demanding to functional groups. Tannic acid (TA) owns abundant phenolic hydroxyl groups, endowing various firm chemical bindings and excellent antioxidant property. To this end, we developed a time-dependent and antioxidant multifunctional coating via TA mediated LbL self-assembly. This layer exhibited higher ROS removal capacity and stronger binding ability. Furthermore, it showed rapid and excellent antibacterial ability of over 85 % against Staphylococcus aureus and Escherichia coli at 24 h, which additionally promoted osteogenic differentiation in vitro in long term. Moreover, the coating exhibited outstanding antibacterial and bone regeneration performance in vivo as well. Thus, this study is expected to provide an antioxidant and time-dependent multifunctional platform for surface modification engineering of dental and orthopedic implantation, as well as other potential biological material designs.

Nacre of Pinctada maxima is a natural biomineralized matrix, appeared 7 million years before hominins. In this study, we converted nacre into a self-setting particle bound with multiple calcium orthophosphates that reassemble mammals’ bone mineral matrices for induction of bone regeneration. The nacre-based calcium orthophosphates composite (NCOC) exhibited a compression strength of 10 MPa, which is superior to human trabecular bone. In vitro bioactivity tests revealed the formation of apatite with nano-porous flake-like crystals on the composite surface that mimic HA structure of a human bone matrix. NCOC demonstrated efficient attachment and proliferation of osteoblast cells, promoting osteogenic differentiation by increasing expressions of RUNX2 and OPN. In vivo studies using rabbit back fascia demonstrated that NCOC displays better bone healing and biocompatibility than conventional bone substitute apatite in critical bone defect models. The degradation of calcium carbonate crystal in vivo does not compromise structural integrity of NCOC. Overall, our data showed that NCOC produced through self-setting reactions, presents advantages such as accelerated biodegradation and osteostimulative properties, making it a promising bone substitute for effective bone regeneration.