Structural Engineering Materials Research Articles

A comparative study on the inhibition of microalgae attachment performance between Cu-based alloy laser cladding layer containing submicron Cr-rich precipitated phases and copper in simulated seawater

Copper alloys are prominent materials in ships and marine engineering structures due to their effective antifouling performance. However, the deposition of insoluble corrosion products dramatically deteriorates their antifouling performance during long-term immersion. To solve this conundrum, we have developed a novel Cu-based alloy cladding layer containing submicron Cr-rich precipitates, which aims to promote the corrosion products flaking through the effect of precipitates, thus effectively inhibiting microalgae attachment. After being immersed for 180 days, the coverage rates of microalgae on the cladding layer were below 2%, while those on the copper exceeded 40%. The remarkable inhibition of microalgae attachment achieved by the cladding layer is mainly due to the Cr-rich precipitates embedded in the unique and loose multi-layer structure corrosion product as Cr2O3-rich particles, which promotes the corrosion product cracking and flaking. Thereby, the cladding layer kills attached microalgae by increasing their reactive oxygen species (ROS) levels.

Large-Size ultrathin mica nanosheets: Reinforcements of biobased PEF polyester

Due to the superior physical properties and high-level alignment of the nanoscale building blocks, assembly of high-quality two-dimensional (2D) nanosheets into macroscopic engineering structure materials can achieve many unexpected performance. Natural mica nanosheets (MNSs) are abundant and with superlative properties, showing huge prospect for engineering structural materials. However, the difficulty of the mass production with large size and high aspect ratio are the current factors that limit this. Inspired by the well-known scotch-tape exfoliation, herein we develop a gummy-tape exfoliation (GTE) method by using liquid oligomers as mediums in ball-milling process to massively produce large-size and ultrathin MNSs. As a confirmation, the obtained MNSs show a record high aspect ratio of ≈1320 and a large actual yield of ∼ 80 %. A transparent biobased aromatic polyester nanocomposite film made of such MNSs and polyethylene furandicarboxylate (PEF) matrix possesses remarkably improved mechanical, barrier properties, and UV-shielding performances at an extremely low filler loading (≤0.5 vol%), making it a novel potential engineering material for packing fields in foods, drugs, and electronic products, etc.

Mathematical Analysis on Dispersion Relation of Rayleigh Wave for an Initially Stressed Magneto-Poroelastic Material with Corrugated and Impedance Boundary

This study showcases the Mathematical modelling of elastic surface waves and the analysis of dispersion relations of Rayleigh-type of wave in an initially stressed homogeneous porous magneto-elastic material having corrugated and impedance boundary exhibitions. Adoption of the classical harmonic method of wave analysis, non-dimensionalization of the resulting equations of motion, and corrugated-impedance boundary conditions produced by the modeled problem are also captured. The dispersion equation was analytically and graphically presented. Effects of the contributing physical quantities, such as impedance and corrugated boundary parameters, on Rayleigh waves for the chosen material are analyzed. The magnetic field’s influences and the wavenumber associated with the corrugated boundary surfaces on the material increase the dispersion relations of the Rayleigh wave profile on the material. In addition, we noted that the dispersion relations of the wave increases for increasing phase velocity and some parameters of voids. Also, a void parameter triggered a decrease on the dispersion profile of the Rayleigh wave when increased while noting some uniform exhibitions from other voids coefficients. This work holds the potential to provide more insights into studies involving displacement distributions in earthquake sciences, stress-strain analysis in Structural Engineering materials, among others.

The Super Tough Saddle of Mantis Shrimp Derived from Strain Transformation Between Helical Fibers and Interlaminar Fibrils

AbstractMantis shrimps deliver one of the fastest strikes with their powerful dactyl clubs. The kinematic energy derived by a saddle storing and releasing mechanical energy with large deformation. As an exoskeleton, the toughness of saddles can achieve a remarkable value ≈15.28 ± 2.32 MJ m−3, which exceeds most bulk natural materials. The excellent toughness of saddles is mainly attributed to the synergy of the helical mineralized fiber architectures and interlaminar fibrils. The interlaminar fibrils connect adjacent mineralized fiber layers closely, enhancing the toughness through viscoelastic deformation during sliding and separating of adjacent layers. They further cooperate with rigid interlacing fiber structure induced by helical structure to transform little normal strain to large shear strain utilizing incompressibility of soft fibrils further to enhance strain energy for toughening. Inspired by unique laminated saddles, the laminate composites are designed with basalt fabrics achieving remarkable fracture toughness to solve the problem of delamination in traditional laminate composites with poor interlaminar toughness. The Mode I and Mode II interlaminar fracture toughness of bio‐inspired laminate composites respectively increase by 44% and 118% reaching 906.8 and 1394.6 J m−2, which provides an innovative bionic strategy for designing new generation structural engineering materials with excellent mechanical properties.

Wood aerogels decorated amino-functionalized MIL-101(Cr) as efficient filter for multistage purification of wastewater

Exploring novel water purifier to efficiently remove heavy metal ions from the wastewater is of vital importance. Inspired by the hierarchical structure of natural wood and the chelation of amino group, a high-efficiency water purifier with ethylenediamine functionalized MIL-101(Cr) octahedrons anchored on the wood aerogel (MIL-101(Cr)-ED/WA) was constructed. Benefiting from the two-pronged approach with the hierarchical structure of the wood aerogel frame for multistage filtration and the –NH2 that capable of chelation with metal ions, the fabricated MIL-101(Cr)-ED/WA exhibits excellent water purification performances, and its adsorption capacity of toxic Pb2+ ions could reach up to 6.46 mmol g−1. Furthermore, it demonstrates superior recyclability without secondary pollution and is also suitable for simultaneous treatment of multiple metal species. In general, this work will broaden the utilization of wood-based structural engineering materials in the treatment of heavy metal wastewater.

Synergistic in-situ reinforcement of lignin and adhesive for high-performance aligned bamboo fibers composites

To replace plastics with bamboo, it is necessary to develop renewable, lightweight, high-strength, damping, and vibration-reducing bamboo structural materials that can be applied in buildings, transportation, and mechanical engineering applications. Here, a low-cost and high-efficiency top-down method was designed for processing natural bamboo into a lightweight and high-strength aligned bamboo fiber composite. This composite used oriented bamboo fibers that had their lignin and hemicellulose removed, which were used as continuous reinforcement materials, and phenolic resin was used as the adhesive, followed by hot pressing. A highly-interwoven structure was formed by the penetration of the adhesive and the combination of strong hydrogen bonds and chemical bonds formed during hot pressing. This resulted in the high performance of the composite, which exhibited a tensile strength of 421.5 MPa, a bending strength of 211.19 MPa, and an impact toughness of 26.7 J/cm2, which were respectively 2.50, 2.09, and 5.7 times higher than those of natural bamboo. Due to its low density (1.08 g/cm3) and specific tensile strength of 390 MPa g−1 cm3, it was superior to commonly used engineering structural materials such as aluminum alloy, steel, and titanium alloy. It also exhibited excellent damping and vibration reduction performance (with the first three damping ratios of 0.75 %, 0.68 %, and 1.75 %) and dimensional stability (with a 24-h water absorption thickness expansion rate of 7.75 %). Due to its excellent mechanical properties and dimensional stability under wet and hot conditions, this composite is expected to replace nonrenewable synthetic materials as a green and sustainable engineering structural material. It may find applications in drone wings, wind turbine blades, and automotive manufacturing.

The high-throughput bridge to the rapid evaluation of fatigue reliability of structural engineering materials

A high-throughput strategy using miniature specimens to evaluate the ASTM-defined fatigue endurance limits of some engineering materials through a high-throughput symmetry bending cantilever beam fatigue testing system is proposed. Employing such a high-throughput testing method for examining some typical engineering materials, we reveal that the fatigue limits obtained by the traditional testing standard can be directly determined by the high-throughput method-obtained fatigue limit multiplied by a suitable conversion factor. Such a high-throughput method was validated theoretically by the proposed crack initiation model and experimentally by the F316 stainless steel specimens subjected to different aging treatments and Gamma-ray irradiation.

Reflections on 50 Years of Pultruded Fiber-Reinforced Polymer Materials in Structural Engineering

Reflections on 50 Years of Pultruded Fiber-Reinforced Polymer Materials in Structural Engineering

The physical, mechanical and fire performance of bamboo scrimber processed with thermal-treated bamboo bundles

Thermal treatment is gaining increasing attention for bamboo modification in practical production due to its advantages of simplicity, effectiveness and environmental friendliness, particularly in the production of bamboo scrimber. The objective of this study is to investigate the effects of two typical thermal modification methods on the physical, mechanical and fire performance of bamboo scrimber, as well as the related physicochemical properties of bamboo bundles for production purpose. The results indicated that the two types of bamboo scrimber processed distinct advantages in terms of physical and mechanical performances. Specifically, the one processed with bamboo bundles treated by superheated steam at a temperature of 200 ℃ (referred to as the “HL group”), exhibited exceptional dimensional stability and fire resistance, while exhibiting slightly lower mechanical properties. Notably, the HL group exhibited a significantly more pronounced hue compared to the LS group, which was treated with saturated vapor at a temperature of 140 ℃. Both demonstrated exceptional water resistance, with the HL group surpassing that of the LS group in either 24-hour room temperature or a combination of boiling-drying cycling treatments. The MORs of the LS group were determined to be 152.3 MPa and 108.5 MPa under dry and wet conditions, respectively, exhibiting significantly higher values than those observed in the HL group. Conversely, the variation of MOEs was found to be opposite. Both MORs and MOEs of the two groups exhibited a significant decrease in wet condition compared to those in dry condition, with reductions linearly correlated to water absorption of the samples. The failure mode of the LS group demonstrated elastoplastic failure characterized by a “Z-shaped”, while the HL group exhibited with a relatively flat cross-section. Furthermore, the HL group demonstrated superior fire performance in comparison to the LS group, and as evidenced by a significantly denser char residue surface with fewer and wider cracks than that of the LS group. The variations of chemical components and microstructures in bamboo can be attributed to variances in the extent of degradation of hemicellulose, lignin, and even cellulose during the thermal modification processes. The water resistance, dimensional stability and fire performance of bamboo scrimber can be significantly improved through thermal treatment, while resulting in a decrease in MOR, particularly for the HL group. The HL and LS groups of bamboo scrimber both exhibited excellent performances, making them suitable for application as structural engineering materials. The work we conducted offers experimental and theoretical support for improve the pre-treatment procedures of bamboo in the manufacturing of bamboo scrimber for structural utilizations.

Application of the Improved POA-RF Model in Predicting the Strength and Energy Absorption Property of a Novel Aseismic Rubber-Concrete Material.

The application of aseismic materials in foundation engineering structures is an inevitable trend and research hotspot of earthquake resistance, especially in tunnel engineering. In this study, the pelican optimization algorithm (POA) is improved using the Latin hypercube sampling (LHS) method and the Chaotic mapping (CM) method to optimize the random forest (RF) model for predicting the aseismic performance of a novel aseismic rubber-concrete material. Seventy uniaxial compression tests and seventy impact tests were conducted to quantify this aseismic material performance, i.e., strength and energy absorption properties and four other artificial intelligence models were generated to compare the predictive performance with the proposed hybrid RF models. The performance evaluation results showed that the LHSPOA-RF model has the best prediction performance among all the models for predicting the strength and energy absorption property of this novel aseismic concrete material in both the training and testing phases (R2: 0.9800 and 0.9108, VAF: 98.0005% and 91.0880%, RMSE: 0.7057 and 1.9128, MAE: 0.4461 and 0.7364; R2: 0.9857 and 0.9065, VAF: 98.5909% and 91.3652%, RMSE: 0.5781 and 1.8814, MAE: 0.4233 and 0.9913). In addition, the sensitive analysis results indicated that the rubber and cement are the most important parameters for predicting the strength and energy absorption properties, respectively. Accordingly, the improved POA-RF model not only is proven as an effective method to predict the strength and energy absorption properties of aseismic materials, but also this hybrid model provides a new idea for assessing other aseismic performances in the field of tunnel engineering.

Inorganic Ionic Oligomers Induced Organic‐Inorganic Synergistic Toughening Enabling Mechanical Robust and Recyclable Nanocomposite Hydrogels

AbstractMechanical robust hydrogels are ideal for applications in energy, environment, biomedicine, and structural engineering materials fields. However, high strength and high toughness are usually in conflict with each other, and simultaneously achieving both of them within a hydrogel has been challenging. Herein an organic‐inorganic synergistic toughening strategy is reported via in‐situ inorganic ionic polymerization of calcium phosphate oligomers within polymer composite networks composed of polyvinyl alcohol chains and aramid nanofibers. The composite hydrogels are provided with a prestress‐induced hierarchically fibrous structure through the assembly, which resulted in the mechanical strength and toughness up to 24.15 ± 1.12 MPa and 15.68 ± 1.78 MJ m−3, respectively, surpassing most toughened hydrogels. Through lamination and crosslinking, bulk hydrogels with controllable mechanical anisotropy and significant energy absorption/dissipation ability are produced. Moreover, the recycling and regeneration of the hydrogels are easily realized owing to the physically crosslinked network and acid‐induced dissolution of the inorganic units of the hydrogels, which lays a foundation for the sustainable large‐scale production and application of the hydrogels. This study provides an alternative approach for the development of mechanical robust and recyclable nanocomposite hydrogels for various applications including soft body armor, flexible electronics, soft robotics, etc.

Mechanical properties of FRP materials at elevated temperature – Definition of a temperature conversion factor for design in service conditions

One of the main concerns about the use of fibre-reinforced polymer (FRP) materials in civil engineering structures is the potential reduction of their stiffness- and strength-related properties when exposed to elevated temperature. This concern, mostly due to the glass transition process underwent by polymeric matrices, needs to be duly reflected in design standards. In the scope of the development of the European Technical Specification CEN/TS 19101: 2022, “Design of Fibre-Polymer Composite Structures”, this paper presents the definition of a temperature conversion factor for in-service conditions to take into account the reduction of FRP mechanical properties with temperature. The first part of the paper briefly describes the basis of design of CEN/TS 19101: 2022 and the framework to consider the effects of environmental conditions on material properties. The second part presents an assessment of recommendations about the reduction of mechanical properties with temperature in existing design guidelines for FRP structures. The third part describes a survey of test data available in the literature concerning mechanical tests at elevated temperature of FRP materials produced with different fibres, resins, shapes and manufacturing methods. The survey shows that the provisions available in existing design guidelines are not always precise and, in some cases, they are non-conservative. Based on this assessment, the fourth and final part of the paper presents the method used to define the values of the temperature conversion factor included in CEN/TS 19101: 2022, which is consistent with the partial factor method of the Eurocodes. The method takes into account (i) the maximum service temperature experienced by the FRP material, (ii) its glass transition temperature, and (iii) the type of mechanical property, namely if it is either fibre- or matrix-dominated. The proposed temperature conversion factor values proved to be adequate considering the test data available in the literature.

Bamboo-Inspired Renewable, High-Strength, Vibration-Damping Composites for Structural Applications

Renewable structural materials derived from natural biological materials can potentially replace non-renewable synthetic materials for civil engineering and transportation applications. Here, inspired by the functional gradient structure of bamboo, we propose a simple and efficient two-step preparation strategy to convert natural bamboo into a lightweight, high-strength, damping, and sound-insulating structural engineering material called densified bundle-laminated veneer lumber (DBLVL). DBLVL was prepared by finely grading and thinning three layers of bamboo slices and removing the lignin and hemicelluloses from the surface of bamboo bundles. This was followed by penetrating the phenol formaldehyde resin and then solidifying and densifying it in situ. DBLVL had superior mechanical properties due to its bamboo-like gradient laminated structure, three-dimensional network distribution of adhesive under high temperature and high pressure, in situ curing, and solid interfacial bonding. It had a specific tensile strength of 297 MPa cm3 g–1, which was superior to those of many other construction materials. The tensile strength of DBLVL reached 363 MPa, and the bending strength reached 219 MPa, which were 97.28 and 92.11% higher than those of natural bamboo, respectively. The impact toughness reached 15.4 J/cm2. DBLVL also showed excellent damping and vibration reduction (the first three damping ratios were 2.35, 1.81, and 2.40%) and dimensional stability (the thickness expansion rate after 24 h of water absorption was 4.43%). Because of its excellent mechanical properties and hygrothermal stability, DBLVL is expected to replace non-renewable synthetic materials as a green and sustainable structural material for engineering applications.

Fiber bundle recombination and gradient uniform lamination to process high-strength and tough bamboo engineering materials

In addition to high strength and stiffness, advanced structural engineering materials and components should also have designability and structural stability. Green building structural materials developed using bamboo face challenges in terms of durability and stability. In this work, we utilize fiber reorganization and gradient uniform lamination a high-strength, high-toughness, uniform and durable outdoor bamboo engineering material- Bamboo Bundle Laminated Veneer Lumber（BLVL) was prepared by the method of. The unique interlayer tight laminated interlocking occlusal structure and the glue nails enhance the interface bonding performance enhanced BLVL performance. The BLVL specific strength, specific modulus, and impact toughness were 267.70 MPa cm3 g−1, 20.73 GPa cm3 g−1, and 13.8 J/cm2, respectively. The density uniformity and dimensional stability were 2.47 and 2.24 times higher than those of the bamboo scrimber (BS), respectively. This work demonstrates the potential to produce lightweight durable structural engineering materials with controllable properties and designable structures from abundant sustainable fast-growing bamboos.

Fatigue-Induced Surface Modification of Zr-Based Metallic Glass under Environmental Conditions.

Metallic glass (MG), an intrinsic heterogeneous structure at the atomic scale, is one of the promising engineering materials with intriguing physical properties. MG often suffers from the fatigue issue caused by the repetitive mechanical loading, but it is still elusive how the local heterogeneity evolves and affects the macroscale fatigue and deformation against bulky external stress. In this study, we investigate the fatigue effect in Zr-Cu-Al ribbon using a bending fatigue method. We used scanning probe microscopy (SPM) in parallel with X-ray diffraction and X-ray photoelectron spectroscopy to figure out the loading effect on the local heterogeneities. The spatially resolved SPM images show that there is a local fluctuation of mechanical and electrical properties on the fatigued side along with morphological deformation compared to the unloaded side. Approaching the broken edge where the fatigue failure occurs, the decaying tendency is not only more dominant but also accelerated by surface oxidation of the fatigued regions. Our study provides a useful guideline on how to monitor structural changes of MGs under fatigue conditions in service and will open a door toward commercialization of high-performance structural engineering materials.

Microstructure and mechanical properties of gradient ultrafine-grained Mg-Gd-Zr alloy

Fabricating gradient structure (GS) is increasingly adopted in structural engineering materials due to the unique combinations of mechanical properties. In the present work, a gradient ultrafine-grained structure with a change in the grain size up to three orders of magnitude from nano to micrometer is prepared on Mg-2Gd-0.4Zr (wt.%) alloy sheet with coarse grains (CG) by sliding friction treatment (SFT). Compared with homogeneous CG structure, the yield strength of GS + CG + GS is improved from 126 MPa to 243 MPa, acquiring an increase of 93%, and maintains an excellent ductility of 25%, showing an extraordinary strength-plasticity combination among the reported GS-containing Mg alloys. Two-beam condition TEM and EBSD analyses reveal that the refined grain structure and grain orientation modification can promote the activation of multiple dislocation slip systems such as <a> and <c+a> slipping in the GS area, which improves the coordinate ability of plastic deformation. In addition, GS + CG + GS owns higher strength, ductility and better strain hardening ability than that of the GS + CG sample. This is because the symmetrical sandwich structure can alleviate the strain localization so exhibits a better work hardening effect and resistance for failure. This work sheds light on the deformation behavior of heterostructured material and provides a new strategy to improve the mechanical properties of wrought Mg alloys.

Grain boundary relaxation induced ultrastrong-and-ductile bulk pure Ni

Both strength and ductility are essential for high-performance engineering structural materials, thus great endeavors have been invested to solve the strength-ductility trade-off of them during recent two decades. Here, we utilized grain boundary (GB) relaxation to circumvent the trade-off in bulk pure Ni through optimizing grain size when literatures tells that GB relaxation can improve strength but ductility. Both tensile strength and uniform elongation of Ni were elevated from 1450 MPa to 2013 MPa and from 2.33% to 5.17%, respectively. The combination of strength and ductility extends beyond the range established by the strongest bulk pure Ni known. Our investigation unraveled that the increased strength was produced by GB relaxation which remarkably mitigated GB softening produced by GB sliding, and that partial dislocation emission from GBs became the dominant plastic deformation mechanism. The dislocation activities inside the grains increased the strain hardening rate (θ). At the same time, enhanced probability of interaction between dislocations and GBs improved the strain rate sensitivity (m). It was the GB relaxation induced dislocation activities that improved θ and m, which stabilized the plastic deformation to enhance ductility. The present work offers a foundation for the ongoing of more advanced engineering structural materials with the advisable design of GB complexion.

Changes in Chemical Composition, Crystallizability, and Microstructure of Decayed Wood-Fiber-Mat-Reinforced Composite Treated with Copper Triazole Preservative

Wood-fiber-mat-reinforced composites (WFMRCs) possess excellent physical and mechanical properties and provide high structural performance, making them a suitable engineering structural material. However, WFMRCs are susceptible to biological attack by fungi and insects when they are used in outdoor environments. In this study, the efficacy of copper triazole (CuAz) preservative treatment in protecting WFMRC against decay by white- and brown-rot fungi (Trametes versicolor and Gloeophyllum trabeum, respectively) was evaluated. Both fungi caused a mass loss in the untreated scrimber of more than 15%, while the CuAz preservative treatment reduced the mass loss to 5%. The measurement results show that CuAz treatment could effectively reduce the degradation rate of three major components of wood; inhibit fungal colonization and degradation; and improve the decay resistance of WFMRC. The atmospheric impregnation of CuAz preservative is more suitable for the material features of WFMRC than vacuum impregnation and can be considered for practical industrial applications. This study provides technical support for the protection and outdoor application of WFMRCs.

Effect of Corrosive Medium and Surface Defect-Energy on Corrosion Behavior of Rolled ZK61M Alloy.

Magnesium alloys have been widely used as lightweight engineering structural materials, but their service performances are severely restricted by corrosion failure. In this paper, the influence of corrosive medium and surface defect energy on the corrosion behavior of rolled ZK61M alloy was investigated. The corrosion tests were conducted in different concentrations of sodium chloride solution for different durations, and the polarization curves and electrochemical impedance spectroscopy were reported. The surface morphology of rolled ZK61M alloy before and after corrosion tests were analyzed. The results showed that the corrosion tendency became stronger with the increase of the concentration of corrosive medium and the number of surface defects of ZK61M alloy. Moreover, the initial corrosion pattern was the pitting caused by micro galvanic corrosion at the surface defect, which gradually developed into uniform corrosion. Furthermore, the main damage occurred at the grain boundary, resulting in the destruction of grain bonding force and the removal of material along the rheological layer. The oxidation corrosion mechanism was mainly the anodic dissolution mechanism.

An alternative approach for measuring the mechanical properties of hybrid concrete through image processing and machine learning

Image processing (IP), artificial neural network (ANN), and adaptive neuro-fuzzy inference system (ANFIS) are innovative techniques in computer science that have been widely used to predict the properties of materials in structural engineering. The stability of reinforced concrete structures mainly depends on the mechanical properties of concrete, i.e., its compressive strength fc and tensile strength ft. Different kinds of inexpensive cement replacement materials (CRM) can be used to form hybrid concrete (HC) with enhanced mechanical and other properties. In this study, the IP, ANN, and ANFIS methods are properly combined and used to predict the mechanical properties of hybrid concrete. For this, 162 cylindrical specimens of HC with 0%, 15%, and 25% silica fume and fly ash as replacement material with three mix ratios, 1:3:6, 1:2:4, and 1:1.5:3 were cast at 14 days and 28 days curing. The specimens were divided into three equal sets as follows: (i) the first to find the compressive strength, (ii) the second to find the split cylinder strength, and (iii) the third to develop a database of images. For the image acquisition, each cylinder of the third set is cut into three slices using a stone cutting saw, resulting in six faces and a total of 324 images (6 × 54). Photos (digital images) are then taken in fully controlled lighting conditions from a height of 600 mm between the concrete surface and the camera lens. The acquired images are pre-processed (converted to grayscale, cropped, and resized to 256 × 256 pixels), and the statistical features are extracted to predict the fc and ft by using ANN and ANFIS techniques. Finally, the predicted values are tested and validated through nondestructive testing methods. The actual values of the compressive and the tensile strength of concrete were compared to the corresponding values estimated by the proposed methods, i.e. (IP, ANN) and (IP, ANFIS). The accuracy of the results largely depends on the data set. The accuracy obtained by IP/ANN is 99.7% while the one obtained with IP/ANFIS is 97.8%.