Functionally graded octet lattice structure for enhancing multifunctional mechanical performance using localized material distribution

Fiber-reinforced plastic laminates containing aligned carbon nanotubes (CNTs) are manufactured by vacuum-assisted resin infusion processing, building on prior extensive work with a hand lay-up process. Three-dimensional reinforcement of the laminates is achieved using long (>10 �m) CNTs in both the interlaminar and intralaminar regions. Radially-aligned CNTs were grown in situ on the surface of alumina fibers in woven fabrics by chemical vapor deposition (CVD), creating a nanoscale, fiber (FF) hierarchical architecture. The multi-scale (nm andm diameter fibers) fiber dry forms are infused using an aerospace standard infusion resin with no modification to the processing or resin. Optical and scanning electron microscope images of composites cross sections confirmed ~0.1% void fraction, and that the CNTs retain alignment and remain on the surface of the fibers after the infusion process. Flexure tests of the fuzzy fiber composites show that in-plane properties (bending modulus and strength) are retained. Combined with prior work on such laminates, these results indicate that the aligned CNTs can provide significant interlaminar toughness enhancement without degrading in-plane laminate properties. This finding is in contrast to typical z-direction laminate reinforcement techniques such as stitching and z-pinning that substantially degrade in- plane properties to achieve interlaminar reinforcement. Additionally, electrical properties of the infusion-processed laminates reveal conductivity enhancement of greater than 10 6 times from the incorporation of ~1% volume fraction of CNTs. The processing demonstrated shows that infusion is a viable fabrication route for new CNT-enhanced composite materials containing aligned CNTs with improved mechanical and multifunctional performance.

This study presents a novel origami-inspired infill design for additive manufacturing (AM) that simultaneously achieves desirable compressive strength and acoustic absorption, validated via fused deposition modeling (FDM). Conventional design approaches limited by the structural geometric design freedom often focus on mono functionality (e.g. mechanical, acoustical, optical, etc), followed by multiple functional structure assembly, or achieving multi-functionality by using material composites. A Kresling-origami cellular architecture was introduced that achieves dual functionality through geometric control alone, demonstrating superior performance to standard infill patterns (Gyroid, Honeycomb, Grid). Parametric determination identified a 90° twist angle with alternating layer direction as the optimal configuration determined by mechanical and acoustic performance scores, yielding a 237.1 N g−1 strength-to-weight ratio (9%–37% improvement over other standard infills) and sound absorption average (SAA) (SAA = 0.36, peak α = 0.68 at 3600 Hz). Experimental validation confirmed the design’s mechanical robustness under compression and acoustic efficacy via impedance tube testing (2000–5000 Hz). Beyond fundamental performance gains, the presented infill shows strong potential for application in multifunctional sandwich shell structures, such as those used in submarines, enhancing both lateral load-bearing capacity and internal noise absorption. This work advances AM by demonstrating that complex, multifunctional performance can be achieved through principled geometric design rather than material heterogeneity.

Microneedle arrays show many advantages in drug delivery applications due to their convenience and reduced risk of infection. Compared to other microscale manufacturing methods, 3D printing easily overcomes challenges in the fabrication of microneedles with complex geometric shapes and multifunctional performance. However, due to material characteristics and limitations on printing capability, there are still bottlenecks to overcome for 3D printed microneedles to achieve the mechanical performance needed for various clinical applications. The hierarchical structures in limpet teeth, which are extraordinarily strong, result from aligned fibers of mineralized tissue and protein‐based polymer reinforced frameworks. These structures provide design inspiration for mechanically reinforced biomedical microneedles. Here, a bioinspired microneedle array is fabricated using magnetic field‐assisted 3D printing (MF‐3DP). Micro‐bundles of aligned iron oxide nanoparticles (aIOs) are encapsulated by polymer matrix during the printing process. A bioinspired 3D‐printed painless microneedle array is fabricated, and suitability of this microneedle patch for drug delivery during long‐term wear is demonstrated. The results reported here provide insights into how the geometrical morphology of microneedles can be optimized for the painless drug delivery in clinical trials.

Self-supported nanoporous lysozyme/nanocellulose membranes for multifunctional wastewater purification

Introduction: Strength and structural stability of the aorta primarily comes from collagen that is mostly found in the media layer of the aorta along with elastin. The risk of life-threatening aortic rupture increases in cases of aortic aneurysm diseases due to local deformation and weakening of the aortic wall. How does local structure affect how the aorta responds to stress? We hypothesize that material and geometric heterogeneity affect the local biomechanics of the aortic wall and that the local responses to stress are not necessarily the same as the global response. Our goal is to develop a novel finite element model (FEM) of collagen and elastin behavior in murine aorta derived from high-resolution micro-computed tomography (microCT). This model will allow us to study how the aorta deforms to blood pressure at the local level. Approach: The collagen and elastin from 100 vertical slices of microCT scans of a murine aorta were segmented, smoothed and meshed to create 3D models for FEM and the aortic ring was divided into 8 sections of varying geometry and composition. Local stress-strain relationships were extracted from uniaxial loading conditions. Simulations were conducted where the stiffness of collagen was set equal to (1X) or made stiffer than elastin by a factor of 10 (10X) or 100 (100X). The average Young’s modulus, E, for each section was calculated and used as parameters for FEM of the aortic ring to investigate the global mechanical behavior of the aortic wall. Results/Conclusions: The strains generated in the radial direction are greater than the strains in the hoop direction in each of the 8 heterogeneous sections of the aortic ring. There was significant variability in the E values in the 10X and 100X systems. FEM of a materially uniform aortic ring yielded smaller maximum principal logarithmic strains compared to a ring that was materially heterogeneous. This study provides evidence that local structure and material distribution are important in aortic biomechanics. Pathogenesis of aneurysmal disease is dependent on collagen and elastin turnover. Aneurysm rupture results from mechanical failure: peak wall stress exceeds local tissue strength. This novel method will allow for development of a complex aortic fracture model to study aortic pathologies.

Additive manufacturing (AM) can ensure the fabrication of complex structures as well as replace conventional parts for extensive modification and cheaper alternatives. Although the mechanical behaviors of different lattice structures have been studied extensively, the corresponding mechanical performances of integrated-manufactured structures with complex infills should be systematically investigated as the usage of 3D-printed parts replacing metals for strength applications can be seen more than ever. The main objective of this study was to investigate how printing factors like infill lattice structure and printing orientation affects the mechanical characteristics of printed samples. Samples were produced via an FDM 3D printer with similar conditions for each case. Kelvin and Octet lattice structures were compared on both horizontal and vertical printed orientations. The test was conducted on a specific geometry, 60mm cubic infill area with top and bottom wall and open sides. The comparison was done based on strength-to-weight characteristics of the samples with fixed weights for all cases. Compression tests using a universal testing machine (UTM) were done on the printed samples. The results of this study demonstrate that infill lattice structure and orientation significantly affect the compression strength of the PLA+ printed samples. The result shows that the lattice structure with unit cell of Octet lattice can withstand higher loads before failure, and the Kelvin lattice structure shows more ductile properties. It can also be seen that the horizontal printing orientation results in superior mechanical properties subjected to top loads than vertical orientation of printing. The research findings are helpful in understanding greater mechanical and physical characteristics that would undoubtedly assist designers and manufacturers worldwide as the FDM 3D printer becomes increasingly crucial in manufacturing engineering parts.

Mandibular reconstructive surgery is necessary for large bone defects. Although various reconstruction methods have been performed clinically, there is no mandibular reconstruction method that meets both sufficient strength criteria and the patient's specific morphology. In this study, the material strength of the cylindrical lattice structures formed by electron-beam melting additive manufacturing using titanium alloy powder was investigated for mandibular reconstruction. The virtual strengths of 28 lattice structures were compared using numerical material tests with finite element method software. Subsequently, to compare the material properties of the selected structures from the preliminary tests, compression test, static bending test and fatigue test were conducted. The results showed that there were correlations with relative density and significant differences among the various structures when comparing internal stress with deformation, although there was a possibility of localized stress concentration and non-uniform stress distribution based on the lattice structure characteristics. These results suggest that the lattice structure of body diagonals with nodes and a cell size of 3.0 mm is a potential candidate for metallic artificial mandibles in mandibular reconstruction surgery.

Tailoring Mechanical Performance in Bulk Nanoparticle-Structured ZnO and Al₂O₃: Insights from Deep Learning Potential Molecular Dynamics Simulations

Improving energy absorption and failure characteristic of additively manufactured lattice structures using hollow and curving techniques

The lattice structure is a type of cellular materials [1] that has truss-like structures with interconnected struts and nodes in a three-dimensional (3D) space. Compared to other cellular materials such as random foams and honeycombs, the lattice structures exhibit better mechanical performance [2]. Some examples of lattice structures are shown in Figure 8.1. The first one is a randomized lattice structure. Due to the disordered lattice cells, the properties of this type of lattice structures are stochastic and difficult to control. But it can be used as implants in orthopedic surgeries. The second and the third are lattice structures with periodic unit cells. The difference is that the strut thickness of the second one is uniform, which is called homogeneous lattice structures. However, the third one has non-uniform strut thickness for specific loading conditions, which is called heterogeneous lattice structures. By properly adjusting the material in vital parts of the lattice structure, the heterogeneous periodic lattice structure can have a better mechanical performance than the homogeneous one with the same weight. Plenty of design and optimization methods [3-5] have been proposed for lattice structures to pursue better performance in different engineering applications. For example, the lattice structure is applied to achieve lightweight [3, 4], energy absorption [6], and thermal management [7]. Due to the complexity of the geometry, the fabrication of lattice structures had been the most critical issue. However, with the development of Additive Manufacturing (AM) processes, the difficulty in the fabrication was largely relieved.

The Tang Dynasty (618–907 CE) palace-style timber frame represents one of the earliest preserved architectural forms in China. To evaluate its mechanical performance and degradation characteristics, a full-solid-element finite element model was developed based on the pseudo-static testing of a single-room timber frame, using the East Main Hall of Foguang Temple as a prototype. Furthermore, multiple timber frame models of varying scales and under different stress conditions were established to analyze global and local stress distributions. Stress distributions under varied loading conditions showed that increasing vertical loads amplify frame deformation and stress magnitudes, with high-stress regions concentrated in the puzuo layer, while single-span frames exhibit significant stress only when horizontal displacement effects on non-loaded spans are <5%. This study quantifies historical timber structures' load-bearing responses to complex stress states, supporting conservation and mechanical property research.

Surface analysis and mechanical behaviour mapping of vertically aligned CNT forest array through nanoindentation

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A 3D X-ray CT method was developed using a combination of a micro-focus X-ray generator and an image intensifier camera. An image processor used produced 2D projection data for CT imaging. The channel number of the data was 1024, and the slicing number was up to 200. A micro-focus X-ray generator was used and image-magnifying method was carried out to imaging porous ceramic materials. Using obtained 3D CT images, voxel mesh method was carried out with mathematical homogenization method. Complicated structures of porous materials were taken into the simulation process as an image-based modeling. Equivalent homogenized elastic constants were calculated for the microscopic porous models, and global macroscopic stress and local stress distribution in porous materials were calculated with the simulation method. This simulation method was considered to be applicable to much larger porous materials of piping and construction.

A non-invasive experimental method and a clustering DEM model were developed in this study to investigate micro-macro behaviors of real granular materials with irregular particle shape configurations. The investigated behaviors include global deformations, failure strengths and residual strengths, stress and strain distributions, local coordination number, local void ratio, particle kinematics, and fabric orientation distributions. The experimental method includes an approach to automatically identify and recognize multiple particles using x-ray computed tomography imaging (XCT) and an enhanced approach to digitally represent microstructures of granular materials. The digitally represented microstructure can be directly employed for numerical simulation setup. A compression test and a direct shear test on coarse aggregates were conducted and analyzed using this method. The experimental measurements were applied for the evaluation of DEM simulations. The clustering DEM model provided in this study extends the conventional DEM model by incorporating actual microstructure of materials into simulations. Real irregular particles were represented by clusters of balls in the clustering DEM model while spherical particles were employed in the conventional DEM model. The PFC3D commercial software was applied for 3D DEM simulations of the compression test and the direct shear test. Compared to the conventional DEM model, the clustering DEM model demonstrated a better capability of predicting both the micro and macro behaviors of granular materials, including dilation, strength, particle kinematics, and fabric evolution. Fabric distribution was investigated for both the conventional DEM model and the clustering DEM model. The clustering DEM model described the fabric distribution of actual materials more precisely. This feature enabled it to simulate micro-macro behaviors of materials more accurately. A theoretic stress-fabric tensor relationship was also evaluated using the simulated stress and fabric distributions based on the actual microstructure of a real material. This relationship incorporated the anisotropic microstructure characteristics of the material. Whether it can better describe behaviors of granular materials was evaluated in this study. Generally, this research provides a more inherent understanding of granular materials through both DEM simulations and experimental validations.