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Organic polymer‐based composite materials with favorable mechanical performance and functionalities are keystones to various modern industries; however, the environmental pollution stemming from their processing poses a great challenge. In this study, by finding an autonomous phase separating ability of fungal mycelium, a new material fabrication approach is introduced that leverages such biological metabolism‐driven, mycelial growth‐induced phase separation to bypass high‐energy cost and labor‐intensive synthetic methods. The resulting self‐regenerative composites, featuring an entangled network structure of mycelium and assembled organic polymers, exhibit remarkable self‐healing properties, being capable of reversing complete separation and restoring ≈90% of the original strength. These composites further show exceptional mechanical strength, with a high specific strength of 8.15 MPa g.cm−3, and low water absorption properties (≈33% after 15 days of immersion). This approach spearheads the development of state‐of‐the‐art living composites, which directly utilize bioactive materials to "self‐grow" into materials endowed with exceptional mechanical and functional properties. [ABSTRACT FROM AUTHOR]

Biological strong and tough materials have been providing original structural designs for developing bioinspired high‐performance composites. However, new synergistic strengthening and toughening mechanisms from bioinspired structures remain yet to be explored and employed to upgrade current carbon material reinforced polymer composites, which are keystone to various modern industries. In this work, from bamboo, the featured cell face‐bridging fibers, are abstracted and embedded in a cellular network structure, and develop an epoxy resin/carbon composite featuring biomimetic architecture through a fabrication approach integrating freeze casting, carbonization, and resin infusion with carbon fibers (CFs) and carbon nanotubes (CNTs). Results show that this bamboo‐inspired crack‐face bridging fiber reinforced composite simultaneously possesses a high strength (430.8 MPa) and an impressive toughness (8.3 MPa m1/2), which surpass those of most resin‐based nanocomposites reported in the literature. Experiments and multiscale simulation models reveal novel synergistic strengthening and toughening mechanisms arising from the 2D faces that bridge the CFs: sustaining and transferring loads to enhance the overall load‐bearing ability and furthermore, incorporating CNTs pullout that resembles the intrinsic toughening at the molecular to nanoscale and strain delocalization, crack branching, and crack deflection as the extrinsic toughening at the microscale. These constitute a new effective and efficient strategy to develop simultaneously strong and tough composites through abstracting and implenting novel bioinspired structures, which contributes to addressing the long‐standingly challenging attainment of both high strength and toughness for advanced structural materials. [ABSTRACT FROM AUTHOR]

High strength concrete (HSC) with superior strength advantage has been gaining widespread attention and engineering endorsement in recent years. For a better understanding of the mechanical responses and failure mechanisms of HSC, a novel three‐dimensional (3D) mesoscale model considering the meso‐structural features of concrete was proposed in this paper. First, a series of uniaxial compressive tests were conducted to investigate the compressive properties of HSC specimens with a strength of 80–90 MPa. After that, a 3D three‐phase mesoscale model consisting of mortar, coarse aggregate, and the interfacial transitional zone (ITZ) between them, was developed to perform the mesoscopic simulations of HSC. Then, systematic analysis and discussions on the compressive properties of HSC were presented in terms of the stress–strain curves, compressive strengths/toughness, failure patterns, cracking process, etc. Results indicate that HSC exhibited obvious brittle failure characteristics, and its strength was significantly related to the water‐to‐cement ratio and mineral admixture. At meso‐level, the cracking behaviors of mortar and ITZ phases were well modeled using the developed mesoscale model. Additionally, it was found that the cracking behavior of HSC was significantly associated with the ITZ characteristics. The developed mesoscale modeling approach has been proven to simulate and investigate concrete's compressive properties in a reliable manner, and can be applied further to the property analysis of concrete materials and structures. [ABSTRACT FROM AUTHOR]

Split Hopkinson pressure bar (SHPB) with 75-mm diameter is used to conduct dynamic impact compression tests on different strength grades of basic magnesium sulfate cement-coral aggregate concrete (BMSC-CAC). The failure process of BMSC-CAC under dynamic impact compression is simulated using the finite element software LS-DYNA and a three-dimensional random aggregate mesoscopic model. The results show that BMSC-CAC has a significant strain rate effect, and the dynamic impact strength increases as the strain rate increases. Because of the high toughness of BMSC, BMSC-CAC has higher energy absorption than coral aggregate seawater concrete (CASC) and sisal fiber coral aggregate seawater concrete (SFCASC). The LS-DYNA software is used for the numerical simulation of the mesoscale dynamic impact compression. The relative error of the peak stress and strain between the test and simulation results is small. Analysis of the failure process indicates that the damage extent of the aggregate increases, and the failure time decreases with an increase in the strain rate. [ABSTRACT FROM AUTHOR]

The penetration resistance of the new material Basic Magnesium Sulfate Cement (BMSC) is studied through comprehensive application of an experimental and numerical simulation method. This paper consists of three parts. The first part introduces the preparation of Basic Magnesium Sulfate Cement Concrete (BMSCC) and the study of its dynamic mechanical properties. In the second part, on-site testing was carried out on both BMSCC and an ordinary Portland cement concrete (OPCC) target, and the anti-penetration performance of the two materials was analyzed and compared from three aspects: penetration depth, crater diameter and volume, and failure mode. In the last part, the numerical simulation analysis was carried out based on LS-DYNA, and the effects of factors, such as material strength and penetration velocity on the penetration depth, are analyzed. According to the results, the BMSCC targets have better penetration resistance performance than OPCC under the same conditions, mainly manifested in smaller penetration depth, smaller crater diameter and volume, as well as fewer cracks. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study on the dynamic splitting tensile properties of ceramic aggregate concrete (CAC) that is composed of ceramic aggregates and mortar matrix. The maximum ceramic aggregate diameter includes 0.3, 0.6, and 0.9 cm. A series of split‐tension tests of CAC specimens were conducted first. Parametric studies such as the effects of aggregate size and strain rate, on the splitting tensile behaviors of CAC were presented in terms of tensile strength, stress–strain curve, failure patterns, and so on. Subsequently, we developed a three‐dimensional two‐phase mesoscale model for CAC, where the random distribution and size characteristics of ceramic aggregates in concrete were fully considered. Employing the developed mesoscopic model, systematic mesoscopic simulations were performed to investigate the mesoscopic responses of CAC under dynamic split‐tension loadings. Results indicated that the mechanic properties and cracking behaviors of CAC are associated with many factors, such as aggregate diameter, aggregate distribution and strain rate. Besides, there was a good agreement between the tested and numerical results, demonstrating that the developed mesoscale model has a significant reliability and potential in simulating the mechanical properties of CAC. [ABSTRACT FROM AUTHOR]

Based on the drying-wetting cycles experiment and the carbonation-drying-wetting cycles experiment for coral aggregate seawater concrete (CASC) with different strength grades, the effects of carbonation-drying-wetting on the durability of CASC are studied with the surface state, mass loss rate, relative dynamic elastic modulus, ultrasonic wave velocity and cube compressive strength as indices. Results show that the mass loss rate of CASC increases gradually with the increase in cycle times in the drying-wetting and carbonation-drying-wetting cycles. The mass loss rate increases relatively slowly at the initial stage but it increases remarkably after 10 cycles. The relative dynamic elastic modulus and ultrasonic wave velocity decrease gradually with the increase in cycle times. After 6 cycles, the decrease rate of the relative dynamic elastic modulus and ultrasonic wave velocity of CASC tends to be flat and the surface is slightly damaged. Compared with the initial 28 d cube compressive strength, the cube compressive strength of CASC decreases by 8.8% to 11.0%. Drying-wetting cycles and carbonation can accelerate seawater erosion on CASC, and drying-wetting cycles result in salting-out and accelerate the destruction of concrete. Therefore, the carbonation-drying-wetting accelerates the destruction of CASC. [ABSTRACT FROM AUTHOR]

Reinforced coral aggregate concrete beam and reinforced ordinary aggregate concrete beam with different concrete type, concrete strength, and steel type were designed in this study to investigate their shear behavior. The shear behavior of reinforced coral aggregate concrete beam was tested, the failure mode and deflection behavior were studied, and the calculating model for the ultimate shear capacity (V cs) of reinforced coral aggregate concrete beam was proposed. Results showed that the failure mode of reinforced ordinary aggregate concrete beam and reinforced coral aggregate concrete beam were basically the same. As the concrete strength increases, the normal section cracking load (V cr), inclined section V cr, and V cs of reinforced coral aggregate concrete beam increased gradually. Furthermore, V cr and V cs of reinforced coral aggregate concrete beam were as follows: 316 stainless steel > common steel > zinc-chromium coated steel > new organic coated steel. For the coral aggregate concrete structure in ocean engineering, in order to prolong its service life, the use of new organic coated steel was suggested. At the same time, the influence of high-strength coral aggregate concrete and stirrup corrosion was comprehensively considered and the calculation model for the V cs of reinforced coral aggregate concrete beam was presented and was then verified. [ABSTRACT FROM AUTHOR]

[Display omitted] • Irregular polyhedron model with controllable shape and size characteristics. • Vector-growth algorithm for controlling convexity and concavity of particle. • An iterative growth algorithm for generating particles with different surface numbers. • Quantitative parametric analysis on shape and size configurations of irregular particles. • Random distribution algorithm for the irregular particles in spatial domain. • Compaction algorithm for controlling volume fraction of particulate system. Particles around us are generally in the form of irregular characteristics in shape and size. Establishing rational mesoscale models that are suitable for different types of particles is of great significance to comprehensively evaluate the mechanical properties of particulate systems assembled from irregular particles. The preponderances of previous works are mainly focused on particle simulations using regular-shaped geometries or simple polyhedrons, and little is known about quantitative characterization for the particles with complex shape characteristics. In this paper, a series of novel and efficient algorithms are presented to generate three-dimensional particulate systems assembled from particles with irregular characteristics in shape and size. According to the developed particle generation algorithm and vector-growth algorithm, the convex- and concave particles with different shape- and size configurations are obtained. Parametric analysis of corresponding algorithm parameters on the shape- and size configurations of particles are quantitatively investigated in terms of different indexes, such as sphericity, angularity and size, which provides an important guidance for the shape- and size control of irregular particles. Based on the generated irregular particles, a series of algorithms are proposed to generate the particulate systems with random spatial characteristics as well. Employing the developed compaction algorithm, mesoscopic particulate systems with different particle gradations and compactness are generated precisely. To sum up, the present particle model provides insights into capturing and studying the meso -structure characteristics and macroscopic mechanical properties of particulate systems. [ABSTRACT FROM AUTHOR]

• State-of-the-art mesoscale modelling approaches and material models for concrete. • Generation methods for different mesoscopic models for aggregate and concrete. • General finite element meshing techniques for mesoscale concrete model. • Material models for mesoscopic modelling of concrete material. • Mesoscopic modelling of concrete materials under static and dynamic loadings. Further understanding of the mechanical responses and the failure mechanism of concrete under different loadings, the mesoscale modelling approach considering the heterogeneity of concrete has drawn extensive attention in investigating its mechanical behaviors. State-of-the-art mesoscale modelling approaches and material models for concrete are presented and compared with our developed 3D random mesoscale modelling approach, in which the randomness of particles in shape and spatial distribution in concrete is considered. This work mainly concentrates on the development and application of the 3D random mesoscale modelling approach in investigating the mechanical behaviors of concrete under static and dynamic loadings. Employing the 3D mesoscale modelling method, the mechanical properties of the ordinary concrete under dynamic compression, split- and direct tension are numerically studied. According to the example applications performed in this work, it is demonstrated that the 3D random mesoscale modelling approach has excellent validity in investigating the mechanical responses of concrete, which provides significant insights into the further development and application of concrete materials and structures under different conditions. [ABSTRACT FROM AUTHOR]

• Uniaxial compressive properties of ecological concrete (EC). • Three-dimensional (3D) random mesoscale modelling approach for EC. • Peak stress and stress-strain curves of EC in compression. • Effects of aggregate-to-cementitious material, water-to-cementitious material, void content, and aggregate size. • Failure pattern, deformation process and failure mechanism. In this study, the uniaxial compressive behaviors of ecological concrete were investigated using experimental and numerical methods. The uniaxial compressive test was performed on the cubic specimens with a side length of 150 mm. The three-dimensional (3D) mesoscopic model with the consideration of random shapes and sizes of aggregates was developed. The parameters considered were the aggregate-to-cementitious material ratio (A/C), the water-to-cementitious material ratio (W/C), the aggregate size, and the void content. The results indicate that the collapse of aggregate caused by the sliding failure of bonding points among aggregates is the main failure mode of ecological concrete under uniaxial compression. The void content and compressive strength of ecological concrete are associated with the A/C and W/C, and the A/C of 6 is suggested as the optimal value. The compressive stress-strain curve consists of three parts, in which the platform period represents the yield period that is relative to the compacting process. Besides, the peak stress and the peak strains in the axial- and lateral directions are related to the void content and aggregate size, and the lateral strain is obviously larger than the axial strain. Through the comparison of numerical and test results, the developed 3D mesoscale modelling approach together with the model parameters has been approved in investigating the compressive behaviors of ecological concrete. [ABSTRACT FROM AUTHOR]

The dynamic compressive behavior of concrete is closely associated with the specimen size effect and the coupling effect of strain rate and specimen size on the compressive properties is something there worthy studying for the development and application of coral aggregate concrete (CAC). A novel 3D mesoscale modelling approach taking the random characteristics of aggregates is developed for the numerical study in the present work. The specimen diameter of numerical cylinder with the slenderness of 1/2 varies from 50 mm to 200 mm, and the strain rate is within the range of 10−3–200s−1. Employing the 3D mesoscale model, the dynamic compressive responses of CAC, i.e., stress-strain relation, failure pattern and process, energy evolution process, etc. have been simulated and analyzed systematically. Both the effect of strain rate and specimen size have been qualitatively and quantitatively discussed. Through the comparison of numerical and existing test data, it is verified that the compressive behaviors of CAC under different conditions could be characterized and predicted using the 3D mesoscale model. In addition, all above-listed properties are related to the strain rate and specimen size at different degrees. The strain rate effect law on the CAC's strength and absorbed energy can be well expressed using a quadratic function and an exponential function, respectively. And the relationship between strength and specimen size can be mathematically formulated by a power function. Furthermore, a coupling effect law of strain rate and specimen size on the strength of CAC has been proposed and validated based on numerical and test data, which is meaningful for the properties prediction of CAC. Image 1 [ABSTRACT FROM AUTHOR]

To explore the specimen aspect-ratio (height-to-diameter ratio) effect on the compressive behavior of coral aggregate concrete (CAC), a three-dimensional (3D) mesoscale modelling approach with considerations of random shapes and distributions for aggregates was developed in the present study. Through the comparison of numerical and available test results, the reliability of the numerical approach for CAC cylinder specimen with various aspect ratios (2–6) was validated. The stress-strain relations, failure patterns and failure processes of CAC in compression were numerically simulated and discussed in succession. Finally, the aspect-ratio effect law on the uniaxial compressive strength of CAC was obtained and compared with that of ordinary concrete. The results indicate that the post-peak branch of the compressive stress-strain curve of CAC tends to steeper with the increase of specimen length, which corresponds to the localization behavior of concrete. In addition, when the height-to-diameter ratio exceeds 2–3, the length of failure zone is close to three times of the specimen diameter (100 mm). Distinctive failure characteristics of each components (i.e., coral aggregate, mortar and ITZ) in CAC with different lengths were presented, and it was found that there is a faster failure process in the shorter specimen and the cracks in the longer specimen would obliquely propagate in the lateral surface. Furthermore, it has been demonstrated that the uniaxial compressive strength of CAC is related to the specimen aspect-ratio, while it becomes insignificant when the aspect ratio exceeds 2.5–3. Image 1 • The specimen aspect-ratio effect on the compressive behavior of coral aggregate concrete. • A three-dimensional (3D) random mesoscale modelling approach considering random shapes and distributions of aggregates. • The compressive stress and strain behaviors, failure patterns and failure processes of CAC. • The aspect-ratio effect law of uniaxial compressive strength. [ABSTRACT FROM AUTHOR]