Manufacturing-induced defects, especially fibre waviness, are well known to substantially reduce the longitudinal compressive stiffness and strength of unidirectional (UD) composite materials. Nevertheless, the three-dimensional (3D) nature of fibre waviness and its effect on material performance have not been comprehensively investigated in the literature. In this work, a microscale model incorporating representative 3D fibre waviness extracted from CT images is developed to more accurately capture these manufacturing imperfections. The 3D waviness mode is generated by combining two basic two-dimensional (2D) waviness forms: a Snake-like pattern to describe in-plane fibre deviation, and a Bridge-like pattern to describe out-of-plane fibre undulation. Furthermore, individual 3D representative volume element (RVE) finite element models specifically featuring both the Snake-like and Bridge-like patterns are independently investigated to isolate their respective influences on mechanical degradation. Microscale RVE models encompassing the integrated 3D fibre waviness, alongside residual stresses arising from the fabrication process, are constructed to simulate the longitudinal compressive response. The stiffness and strength predicted by these simulations show high correlation with experimental results. This confirms that the proposed micromechanical modelling approach, with residual stress effects accounted for, can effectively capture the influence of complex 3D waviness on the longitudinal compressive behaviour of UD composites.

This paper presents comprehensive experimental testing and numerical modelling of the failure behaviours of unidirectional carbon fibre reinforced polymer (UD-CFRP) composite laminae under multiaxial loading conditions. A novel modified Arcan test rig with a rotational clamp was developed to enable multiple stress combinations with out-of-plane stresses in UD laminae on a traditional laboratory-based uniaxial test machine. The test rig was verified by uniaxial tension and validated by off-axis tension. UD CFRP laminae were tested for the first time under five stress combinations using the test rig, with results cross-validated against a highfidelity representative volume element (RVE)-based 3D micromechanical finite element model. Failure strength envelope and damage mechanisms demonstrate the applicability of the test rig for composite failure under multiaxial loading conditions with abroad spectrum of stress combinations.

With the rapid development of aerospace and defense industries, the shape of products is becoming more and more complex, and the requirements for product processing accuracy and surface quality as well as tool life are getting higher and higher. Ultrasonic elliptical vibration cutting (UEVC) can overcome the limitations of traditional cutting methods in difficult-to-machine materials, high surface integrity and high performance and have been widely used, especially in the processing quality and performance assurance of hard and brittle materials such as ceramics, glass, composite materials and cemented carbide. At the same time, in the expansion from the field of manufacturing and processing to the fields of biomedicine and micro–nano-manufacturing, the requirements for precision are almost strict, which poses higher challenges to UEVC technology and its devices. With this trend, many new UEVC devices and applications have been put forward, however, few people have studied them from a comprehensive perspective. In order to fill this gap in literature and understand the development trend of UEVC, this study gives an important overview of UEVC, including its cutting characteristics, device development and application in difficult-to-machine materials. Firstly, the advantages brought by the cutting characteristics of UEVC are analyzed. Next, the development status and shortcomings of UEVC devices with different excitation modes in structural design and optimization are discussed, and their advantages and disadvantages are compared and analyzed. Then, the application of UEVC in difficult-to-machine materials in recent years is expounded, and the influence of various cutting parameters on tool wear and surface quality is analyzed. Finally, a summary of the full text is made, and several prospects for the future development of UEVC are proposed, which points out the direction for future research.

Cutting tools have long been essential across diverse fields, including mechanical processing, agriculture, biomedical applications, and geological exploration. However, traditional tool design faces limitations due to factors such as cutting environments and conditions. In response, bionic design—drawing inspiration from nature’s evolutionary solutions—has emerged as a transformative approach. Over billions of years, organisms have evolved unique characteristics, such as anti-adhesion, abrasion resistance, and self-sharpening, that can be applied to enhance cutting tool performance. However, the underlying logic and coupled design principles of interdisciplinary and cross-field bionic tool designs are crucial for the optimization of tool bionics, yet have not been systematically studied. Capturing the research hotspots and trends in this field is meaningful, despite the challenges associated with such research. To address this gap, this review paper systematically examines the bionic design of cutting tools, focusing on the mechanisms underlying their superior performance and the achievements and limitations of coupled design strategies. By elucidating the benefits of five types of bionic cutting tools and exploring their bionic coupling design, performance and bionic tool fabrication technology, this review aims to provide a comprehensive understanding of current advancements and identify future research directions. The findings underscore the importance of integrating biological principles into tool design and offer valuable insights into the evolving field of bionic cutting tools.

This research delves into the failure mechanisms exhibited by unidirectional Carbon Fiber Reinforced Polymer (CFRP) composites under longitudinal compression, while considering the interplay of three types of manufacturing-induced defects: initial waviness of fibres, void volume fraction, and void size. The study employs 3D high-fidelity intact representative volume element (RVE) models, incorporating the initial waviness of fibres and voids based on Micro-CT imaging. A novel algorithm is proposed to generate more accurate 3D void shapes, departing from conventional circular or triangular approximations. The results highlight the substantial influence of the initial waviness angle on the reduction of predicted compressive stiffness and strength. The volume and size of voids play a significant role in determining damage initiation within the composites. The failure mechanisms of the composite under the coupled effects of initial waviness of fibres and voids are discussed, exhibiting reasonable agreement with experimental observations.

Inspired by the fact that the architecture of natural biomaterials has a great influence on their mechanical properties, the present work designed a Al2O3–poly (methyl methacrylate) composite with an interlocked wood-like architecture, which can balance the contradictions between flexural strength–fracture toughness. The results shows that the mechanical performance of the composites can be tuned through the adjustment of the tilt angle of the Al2O3 spiral fibres. The composite with a tilt angle of 30° exhibited the highest flexural strength and fracture toughness, showing the ability to overcome the trade-off between flexural strength and fracture toughness. All composites exhibited weak compressive strength anisotropy owing to the interlocked helical architecture in which the continuous fiber spiraled in 3D space. Toughening mechanisms including crack deflection, crack bridging, crack bifurcation, microcracking were observed. Numerous microcracks were nucleated in the Al2O3 ceramic skeleton, and they propagated along the main crack under the bridging effect of poly (methyl methacrylate). All of the composites featured suture-like cracks perpendicular to the direction of the main cracks, which was a unique toughening mechanism found in this architecture. Large-size composites can be prepared through the adopted technique to meet the demands of engineering applications.

Carbon fibre reinforced polymers (CFRP) are prone to structural damage during extreme events such as fire. Typically, modelling the effect of fire on CFRP structures is carried out through mesoscale analysis to predict overall structural performance. In this study, Finite Element (FE) modelling has been conducted to investigate the effects of fire on CFRP specimens at both meso- and micro-scales. The mesoscale analysis informs the microscale analysis to examine the effects of fire on each constituent of the material. A comparison of thermal analysis at the meso- and micro-scales reveals less than a 6% difference in the predicted nodal temperature. For the first time, fire-induced progressive failure analysis has been conducted on the fibres, matrix, and fibre/matrix interface of representative plies within the composite laminates. Fibre breakage, matrix cracking, and interface debonding were accurately captured using representative volume element (RVE) models under thermo-mechanical loading, showing qualitatively excellent agreement with experimental data.

Temperature is one of the seven fundamental physical quantities. The ability to measure temperatures approaching absolute zero has driven numerous advances in low-temperature physics and quantum physics. Currently, millikelvin temperatures and below are measured through the characterization of a certain thermal state of the system as there is no traditional thermometer capable of measuring temperatures at such low levels. In this study, we develop a kind of diamond with sp 2 - sp 3 composite phase to tackle this problem. The synthesized composite phase diamond (CPD) exhibits a negative temperature coefficient, providing an excellent fit across a broad temperature range, and reaching a temperature measurement limit of 1 mK. Additionally, the CPD demonstrates low magnetic field sensitivity and excellent thermal stability, and can be fabricated into probes down to 1 micron in diameter, making it a promising candidate for the manufacture of next-generation cryogenic temperature sensors. This development is significant for the low-temperature physics researches, and can help facilitate the transition of quantum computing, quantum simulation, and other related technologies from research to practical applications.

Molecular dynamics (MD) simulations have become a pivotal tool in the nanofabrication of semiconductor materials, a key area of contemporary semiconductor process research. This methodology has not only facilitated the exploration and optimization of semiconductor materials but has also significantly contributed to enhancing the performance of semiconductor devices by providing a deep understanding of their intrinsic properties. This paper systematically analyzes the methodologies employed in the nanofabrication of semiconductor materials, with a focus on elucidating the mechanical mechanisms and microstructural changes that occur during processing. We introduce and evaluate simulation models for innovative processing techniques such as surface texture, ion implantation, laser-assisted machining, and vibration-assisted machining. These methods demonstrate significant potential for improving processing efficiency and quality. Additionally, this article addresses the challenges in model optimization, including the refinement of potential functions, reaction force fields, chemical reaction prediction, and the development of advanced equipment. Finally, we outline future research directions, emphasizing the continued evolution and application of MD simulations in semiconductor material processing.

Abstract Temperature is one of the seven fundamental physical quantities. The ability to measure temperatures approaching absolute zero has driven numerous advances in low-temperature physics and quantum physics. Currently, millikelvin temperatures and below are measured through the characterization of a certain thermal state of the system as there is no traditional thermometer capable of measuring temperatures at such low levels. In this study, we develop a kind of diamond with sp 2-sp 3 composite phase to tackle this problem. The synthesized composite phase diamond (CPD) exhibits a negative temperature coefficient, providing an excellent fit across a broad temperature range, and reaching a temperature measurement limit of 1 mK. Additionally, the CPD demonstrates low magnetic field sensitivity and excellent thermal stability, and can be fabricated into probes down to 1 micron in diameter, making it a promising candidate for the manufacture of next-generation cryogenic temperature sensors. This development is significant for the low-temperature physics researches, and can help facilitate the transition of quantum computing, quantum simulation, and other related technologies from research to practical applications.

This study presents a data-driven, probability embedded approach for the failure prediction of IM7/8552 unidirectional carbon fibre reinforced polymer (CFRP) composite materials under biaxial stress states based on micromechanical modelling and artificial neural networks (ANNs). High-fidelity 3D representative volume element (RVE) finite element models were used for the generation of failure points. Fibre failure and the friction between fibres and matrix after fibre/matrix debonding were taken into consideration and implemented as VUMAT subroutines, respectively. Uncertainty quantification was conducted based on a coupled experimental–numerical approach and failure probabilities were inserted into the failure points to generate the database for the training of ANNs. A total of 15 biaxial stress combinations were considered for the generation of datasets. Two strategies were considered for the construction of form-free failure criteria based on the ANNs for regression and classification problems. It is found that for the regression problems, an ANN model with 2 hidden layers and 64 neurons can achieve a mean square error (MSE) of 0.027% and a mean absolute error (MAE) of 0.78%. For the classification problems, an ANN model with 3 hidden layers and 32 neurons, presents an excellent performance in the prediction with a probability of 98.1%. A good agreement was observed between the failure strength of composites under transverse and in-plane shear predicted by these ANNs and failure envelopes theoretically predicted by Tsai–Wu and Hashin failure criteria.

Shape-morphing ceramics with complex geometries can be applied in several scenarios; however, the fabrication of such structures remains challenging owing to the brittleness and stiffness of ceramics. This paper proposes a direct four-dimensional (4D) printing technology for achieving and precisely controlling complex ceramic ar-chitectures that may be transformed, in a free-standing manner, from a pre-programmed gradient structure after sintering without intervention of a manual physical force and stimuli. The proposed method involves three steps: printing, curing, and sintering. The designability and flexibility of the proposed approach were demonstrated by preparing different topologies, such as fingers in a palm (multi-curvature), leaves (anisotropic morphing), a dragonfly (high-precision localised deformation), and an intricate structure (self-locking). The obtained ceramics exhibited excellent mechanical properties. This study can help establish a novel paradigm for designing ceramics with complex structures, with potential for application in various fields such as aerospace and biomedical engineering.

Inter-fibre failure analysis of carbon fibre-reinforced polymer (CFRP) composites, under biaxial loading conditions, has been a longstanding challenge and is addressed in this study. Biaxial failure analysis of IM7/8552 CFRP unidirectional (UD) composites is conducted under various stress states. Two widely accepted failure criteria, the interactive Tsai-Wu and non-interactive Hashin failure criteria, are comprehensively assessed with finite element-based micromechanical analysis. High-fidelity three-dimensional representative volume elements (RVEs) are subjected to biaxial loadings with imposed periodic boundary conditions. Carbon fibres are assumed to be transversely isotropic and linearly elastic. The Drucker-Prager plastic damage constitutive model and cohesive zone model are utilised to simulate the mechanical response of the matrix and fibre-matrix interface, respectively. Coulomb friction is assumed between the fibres and matrix after interface failure. Two sets of biaxial loading scenarios (i.e. transverse stress dominated and shear stress dominated) with the associated failure modes are selected for the failure analysis and assessment of these failure criteria. A data-driven failure envelope for the composites under biaxial loadings is developed using a univariate cubic spline function. Failure mode transition points are determined under biaxial loadings. It is found that the micromechanics-based numerical model is effective in assessing these two existing criteria.

The recent decades have seen various attempts at the numerical modelling of fibre-reinforced polymer (FRP) composites in the aerospace, auto and marine sectors due to their excellent mechanical properties. However, it is still challenging to accurately predict the failure of the composites because of their anisotropic and inhomogeneous characteristics, multiple failure modes and their interaction, especially under multiaxial loading conditions. Micromechanics-based numerical models, such as representative volume elements (RVEs), were developed to understand the progressive failure mechanisms of composites, and assessing existing failure criteria. To this aim, this review paper summarises the development of micromechanics-based RVE modelling of unidirectional (UD) FRP composites reported in the literature, with a focus on those models developed using finite element (FE) and discrete element (DE) methods. The generation of fibre spatial distribution, constitutive models of material constituents as well as periodic boundary conditions are briefly introduced. The progressive failure mechanisms of UD FRP composites simulated by RVEs under various loadings are discussed and the comparison of failure envelopes predicted by numerical results and classical failure criteria are reviewed.

This study proposed a novel approach based on the 3D discrete element method (DEM) to simulate the progressive delamination in unidirectional carbon fibre reinforced polymer (CFRP) composite laminates. A hexagonal packing strategy was used for modelling 0∘ representative plies, the interface between different plies was modelled with one bond and seven bonds following the conservation of energy principle and a power law. The number of representative layers and the stiffness of bonds within these layers were calibrated with a comparison of results obtained from finite element method and theoretical analysis. DEM simulations of delamination with both interface models were conducted on unidirectional composites for double cantilever beam (DCB), end-loaded split (ELS) and fixed-ratio mixed-mode (FRMM) tests. It was found that the seven-bond interface model has a better agreement with experimental data in all three tests than the one-bond interface model by adopting the proposed seven-bond arrangement in terms of the progressive delamination process. The main advantages of the present interface model are its simplicity, robustness and computational efficiency when elastic bonds are used in the DEM models.

This paper presents an experimental study on 3D printing of continuous carbon fibre reinforced thermoset epoxy composites. Powder-based solid epoxy was electrostatically flocked on the 1K continuous carbon fibre tow and then melted to fabricate composite filaments. The produced filament was printed using a modified extrusionbased printer which melted and deposited the filament following designed printing paths, to form multilayer preforms with complex geometries. After vacuum bagging and oven curing, high tensile strength (1372.4 MPa) and modulus (98.2 GPa) were obtained in the fibre direction due to the good wettability of epoxy and the consequent high fibre volume fraction (56%). The tensile tests of open-hole composites were also conducted, in which the sample with designed stress-lines fibre paths was seen to improve the ultimate strength by 95% compared with the mechanically-drilled sample. Other case studies, such as a spanner and a lattice structure, further demonstrated the design freedom of produced filaments for complex geometries.

Research development of stimuli-actuated materials has become a crucial driving force in advancing the frontiers of smart devices. Among various responsive mechanisms, localized and remote control can be offered by light stimuli. However, flexible design with complex geometries and multi-level functions for light-triggered reconfigurable structures remain significant challenges. Here, selectively kirigamipatterned reconfigurable structures based on light-responsive material are reported and their applications in biomimetic actuators and flexible electronics field are explored. More than a dozen sophisticated kirigami patterns are fabricated, programmable shape transformations from planar sheets are achieved reversibly under light illumination with finite element analysis guidance. Three biomimetic actuators composed of reconfigurable structures are generated with programmable and remote actuations. Furthermore, to extend functions of this strategy to flexible electronics field, a reconfigurable monopolar antenna is demonstrated. Three states of the antenna can be regulated and switched by light with different power densities. These results pave a facile scheme to realize the flexible and intricate design of light-controlled actuators with multiple functions.(c) 2022 Elsevier Ltd. All rights reserved.

Biomaterials,often imparted time-dependent mechanical properties,which are promising in fields rang-ing from sensors to robotics.Here,a facile method was proposed to fabricate post-tunable mechanical properties composites based on hydrogels and ceramic nanofiller.The wide tunable range of Young's modulus(27.3 kPa to 3.5 GPa)and ultimate stress(173 kPa to 102 MPa)can be achieved by combin-ing solvent absorption and evaporation process with platelets reinforcement effect.Additionally,a large fracture toughness(～32,000 J m-2)is obtained as a result of the nacre-liked"brick and mortar"structure introduced by shear force during fabrication.The superior flexibility and designability of this material were demonstrated via actuators,portable structure,and metamaterials.Above all,this study provides a new thought to fabricate tough materials with post-tunable mechanical properties.

This study presents a hybrid method based on artificial neural network (ANN) and micro-mechanics for the failure prediction of IM7/8552 unidirectional (UD) composite lamina under triaxial loading. The ANN is trained offline by numerical data from a high-fidelity micromechanics-based representative volume element (RVE) model using the finite element method (FEM). The RVE adopts identified constituent parameters from inverse analysis and calibrated interface strengths form uniaxial and biaxial tests. A hybrid loading strategy is proposed for the RVE under triaxial loading to obtain the failure points on sliced surfaces whilst maintaining the constant stress at different surfaces. It has been found that the ANN algorithm is robust in the failure prediction of the UD lamina when subjected to different triaxial loading conditions, with over 97.5% accuracy being achieved by the shallow ANN model, where only two hidden layers and 560 samples are used. The predicted 3D failure surface based on trained ANN model has an elliptical paraboloid shape and shows an extremely high strength in biaxial compression. The approach could be used to inform the modification of existing failure criteria and to propose ANN-based failure criteria.

Additive manufacturing (AM), also known as three-dimensional (3D) printing, has boomed over the last 30 years, and its use has accelerated during the last 5 years. AM is a materials-oriented manufacturing technology, and printing resolution versus printing scalability/speed trade-off exists among various types of materials, including polymers, metals, ceramics, glasses, and composite materials. Four-dimensional (4D) printing, together with versatile transformation systems, drives researchers to achieve and utilize high dimensional AM. Multiple perspectives of the AM of structural materials have been raised and illustrated in this review, including multi-material AM (MMa-AM), multi-modulus AM (MMo-AM), multi-scale AM (MSc-AM), multi-system AM (MSy-AM), multi-dimensional AM (MD-AM), and multi-function AM (MF-AM). The rapid and tremendous development of AM materials and methods offers great potential for structural applications, such as in the aerospace field, the biomedical field, electronic devices, nuclear industry, flexible and wearable devices, soft sensors, actuators, and robotics, jewelry and art decorations, land transportation, underwater devices, and porous structures.