Behaviour Of Materials Research Articles

Evaluation of tensile strength and flexural strength of GFRP composites in different types of matrix polymers

Resin selection has a crucial role in determining the properties and performance of GFRP composites; this study aims to investigate the effects of different resin types, specifically epoxy, bisphenol, ripoxy, and polyester, on the mechanical strength of GFRP composites.The composites were fabricated using the conventional method of hand lay-up technique with a fiber to matrix ratio of 60:40 wt%. The glass fibre laminate arrangement consists of 4 layers, two layers of Woven Roving Mat (WRM) fibres (0/90) and 2 layers on the outer side of the Chopped Strand Mat (CSM). The composite specimens were molded using the ASTM D-838 tensile test standard and ASTM D-790 for the bending test.The research results found that the maximum tensile strength was obtained by GFRP composite with ripoxy matrix type of 181.6 MPa, strain of 0.028%, and flexural strength of 1387 MPa. Composites using polyester matrices can generally be classified as splitting in multiple areas where failure occurs in various areas, but the composite has very high strength.Material experiments conducted on a scientific laboratory scale may not fully reflect the behaviour of composites in actual conditions. Furthermore, aspects such as environmental influences, sustained stresses, or fatigue effects may need to be considered in further research. This evaluation also does not consider the effects of long-term exposures or ageing on the mechanical properties of GFRP composites. Investigating the behaviour of materials over long periods can provide important insights into their durability and reliability in practical applications.In GFRP composites, the application of resin to the fibres is critical. The performance and mechanical characteristics of GFRP composites are largely determined by the polymer matrix. Composites with epoxy, polyester, or bisphenol matrices can be compared to composites with the most equivalent tensile strength values, but composites with ripoxy matrices can be suggested. However, the GFRP composite with bisphenol matrix has an excellent bending strength value. As a result, numerous applications exist for implementing matrix selection in producing GFRP composites.The reliability of the tensile properties of GFRP composites was obtained using the ripoxy matrix type. Furthermore, the reliability of the flexural properties of the composites was obtained using the bisphenol matrix type.

Passively morphing trailing edge design for composite tidal turbine blades

Numerical simulations and lab-scale experiments are used to evaluate three passively morphing trailing edge designs for a composite tidal turbine blade. The designs include a closed trailing edge, an open trailing edge, and a corrugated trailing edge. It is shown that geometric stiffness, as well as material stiffness, play key roles in achieving the desired deformation of the trailing edge. One trailing edge design is down-selected for further investigation via full-scale numerical simulations. These simulations demonstrate how the composite lay-up influences the morphing response of the trailing edge and its likelihood of material failure. The influence of camber is also investigated in terms of both material behaviour and hydrodynamic performance. Finally, the potential for bend-twist coupling of the laminate skins is explored.

3D morphology of the petal-like precipitates in Cu-Fe alloys: Experimental study and phase field modelling

Precipitation hardening is a well-known phenomenon which is widely harnessed in alloy design strategy. In particular, the microstructural features such as shape, size, precipitate number density and volume fraction determine the mechanical behaviour of materials. During service, the morphology of precipitates sometimes achieves a complex 3D shape upon displaying branching and/or splitting patterns. Unfortunately, the detailed information about this intricate morphology cannot be retrieved through traditional experimental techniques based on 2D visualization. Here, we report the implementation of a 3D analysis technique combining Focused Ion Beam (FIB) and Scanning Electron Microscopy (SEM) tomography to visualize the atypical petal-like morphology of Fe-rich precipitates in a Cu-Fe alloy. Using Phase-Field modelling (PFM), we identify the mechanism responsible for the unusual morphologies of Fe-rich particles. Our work highlights the significance of 3D characterization of precipitates and provides a fascinating pathway for refining understanding of precipitation mechanisms in metals and alloys.

Suitability of using simulated porous‐like solutions to evaluate the steel corrosion in carbonated concrete

AbstractThe use of simulated solutions is a common practice in corrosion studies to assess easily and quickly the corrosion behaviour of materials in real situations. In this context, it is frequent to substitute tests performed in concrete or mortar with tests performed in porous‐like solutions. Particularly, to simulate carbonated concrete, different carbonated porous‐like solutions (CPS) are found in the literature. However, it is not known whether the use of these solutions accurately predicts the behaviour of steel bars embedded in carbonated concrete. In the present work, a comparison between the corrosion behaviour of carbon steel in carbonated mortar and in different CPS was performed. It was found that none of the CPS studied in the present work adequately simulate the corrosion behaviour of the steel in carbonated mortar, but the CPS containing high concentrations of carbonates/bicarbonates is the only one that provides corrosion rates close to those obtained in carbonated concrete.

Elastic properties and compressive mechanical behaviour of closed-cell porous materials: Effect of microstructural morphology

This paper studies the effect of different combinations of morphological parameters of porous closed-cell materials on their elastic properties and mechanical behaviour. Three-dimensional representative volumes of porous media with different polyhedral void shapes are investigated, considering variation of statistical realisations of morphological features, such as shape, size and distribution of pores. Description of morphology of each investigated representative volume is formalized using second- and fourth-order correlation functions. The effective properties of representative volumes are calculated with finite-element analysis. Additionally, samples of the studied models were additively manufactured with polystyrene, using fused filament fabrication (FFF/FDM) 3D-printing technique, and subjected to compression. Experimental results for elastic mechanical properties and distributions of strain fields on the surface of the samples, obtained with micro-DIC (digital image correlation), are compared with results of numerical finite-element computations. This is accompanied by analysis of internal-stress distributions to assess the mechanical state of the structures. Patterns and trends observed in mechanical responses of porous materials depending on their different morphological parameters are outlined and discussed.

Assessment of cyclic deformation behaviour of wire arc additively manufactured carbon steel

Wire Arc Additive Manufacturing (WAAM) has gained popularity due to its speed and cost-effectiveness. However, the current knowledge on the cyclic deformation behaviour of WAAM materials is limited. To address this issue, this study investigates the cyclic deformation behaviour of WAAM ER70S-6 carbon steel. Coupons were extracted from printed walls with horizontal and vertical orientations and from surface and interior locations. Low-cycle fatigue tests were performed under fully reversed strain-controlled conditions, spanning strain amplitudes from 0.20 % to 1.50 %. Regardless of the group, the material exhibited cyclic hardening for strain amplitudes above 0.60 % and cyclic softening for smaller strain amplitudes. Significant non-Masing hysteretic behaviour was also observed. Cyclic stress–strain curves and fatigue-life relationships written in terms of stress, strain and energy-based parameters were derived for all groups. Fatigue life was not significantly influenced by printing orientation or location across thickness. However, horizontal orientation resulted in a slightly superior fatigue response. A statistical analysis revealed no significant difference in the accuracy of fatigue-life relationships between the groups. Finally, a comparative study between WAAM materials and conventional steels showed promising results. Yet, conventional steels outperform WAAM carbon steel, at least doubling the fatigue life for the same value of the damage parameter.

A facility for studying corrosion via in-situ Raman spectroscopy

Several in-core components in nuclear power systems are exposed to high-temperature water in the presence of radiation fields. The dynamic effect of radiation and water chemistry on material performance in these environments is not well understood partly due to significant experimental challenges. A facility consisting of a high temperature/pressure corrosion loop coupled with in-situ Raman spectroscopy has been commissioned to examine material behaviour in more realistic reactor conditions. The in-situ Raman component of the facility has been validated by conducting experiments with both pre-oxidized, and freshly abraded SS304L in water at 80 °C and 300 °C. Testing in water also revealed the detection limitations of the system. The assessment reported in this paper highlights the capabilities to perform degradation studies of key nuclear components by conducting in-situ characterization of materials exposed to high temperature water via Raman spectroscopy, thereby providing chemical, structural and semi-quantitative kinetic information.

New insights into early-stage time-dependent dielectric characteristics coupled with frequency dependency and hydration-driven reaction of hydraulic cement pastes: Experiments and statistical modelling

In the field of cement and concrete materials engineering, a comprehensive understanding of dielectric properties is crucial for optimising hydraulic cement paste mix designs. This study examines the relationships among the dielectric constant (ε’), loss tangent (tan δ), frequency, hydration time, water content and admixture dosage in different compositions of hydraulic cement paste. A consistent pattern can be observed across the frequency spectrum, where dielectric constants decrease as frequency increases. This aligns with the expected behaviour of cementitious materials. The most notable finding is the inversely proportional relationship between the loss tangent and frequency. As the frequency increases, the loss tangent consistently decreases, indicating improved energy retention and reduced dissipation. This characteristic is of significant value for various applications, including sustainable infrastructure and smart materials. Furthermore, the interactions among hydration time, water content and admixture dosage present an opportunity for dynamic optimisation within the cement paste matrix. These factors collectively impact dielectric properties, providing insights into the potential for tailored material performance and durability, especially in applications where dielectric properties are critical, such as sensing applications and structural health monitoring of concrete structures. This study emphasises the importance of customising cementitious compositions for specific applications in cement and concrete materials engineering. It achieves this through a detailed comparative analysis of different compositions, each representing varying water content and admixture dosage levels. This approach has the potential to significantly transform the field by enabling engineers to create hydraulic cement pastes with customised dielectric properties that meet the specific requirements of construction, infrastructure and other related applications.

A nonlinear finite viscoelastic formulation relative to the viscous intermediate configuration applied to plants

AbstractIn the contribution at hand, a new formulation for finite strain viscosity relative to the viscous intermediate configuration is presented. The evolution of the viscous deformations is based upon a new numerical approach, which allows for a consistent consideration of anisotropic finite strain viscoelasticity, according to the authors knowledge. A standard Maxwell model is used to describe viscous behaviour at finite deformations. Furthermore, the orthotropic Yeoh material model is extended to include a distinction between behaviour under tensile and compression loading. The proposed formulation is validated, and parameters of the model are identified by material tests on Sorghum bicolor plants. Subsequently, numerical examples are shown to demonstrate the capabilities of the model. In general, the proposed Yeoh material formulation is shown to accurately represent the inability of fibres to carry compression loading. Furthermore, the viscoelastic approach, developed relative to the viscous intermediate configuration, is demonstrated to be capable of producing plausible results. Additionally, the mechanical behaviour of Sorghum bicolor plants is simulated using the introduced formulation. The results show that the contribution at hand describes a novel methodology to simulate the viscoelastic behaviour of plant materials reliably.

Modelling of hybrid biocomposites for automotive structural applications

The demand for environmentally friendly materials is at its peak, and government legislations have become stricter and no longer tolerate violations. With biocomposites emerging as structural components instead of being hidden as non-structural applications and interiors, the automotive and motorsport sector started considering them for structural body parts. Natural fibres abundance, commercial availability, renewability, low density, low cost, and high tensile strength make biocomposite materials excellent candidates for eco-friendly vehicles. Several studies reported the utilisation of biocomposites as high-performance components and structural applications. However, current computer-aided engineering and modelling tools are insufficient to explore the vast field of possibilities during biocomposite materials selection to accurately predict the components' behaviour and analyses. Therefore, this study focuses on creating a material model to predict the behaviour of biocomposite materials. Additionally, the model is numerically implemented to illustrate the deformation and bending stiffness capabilities of a motorsport monocoque chassis structure application. A micromechanics modelling combining rate-dependant constitutive laws and multi-site interactions of inclusions is developed for studying the nonlinear response of composite materials. To avoid numerical instabilities when increments of time become very small, a regulation procedure concerning the visco-plastic function is adopted in the computation of the consistent tangent modulus. Based on the Generalised Mori–Tanaka (GMT) scheme, the effective properties are obtained for the nonlinear composite. The accuracy of the model is evaluated and validated by comparison results from the open literature. Finally, the developed constitutive equations are implemented as a user-defined material UMAT in a Finite Element code, leading to an application on a bio-based composite for the bamboo/flax fibre-reinforced epoxy hybrid composite materials.

Investigation of the impact of fiber incorporation on the properties of high belite cement

In contrast to ordinary portland cement (PC), the manufacturing process of high belite cement (HBC) boasts superior resource utilization, reduced energy consumption, and diminished greenhouse gas emissions. Additionally, HBC exhibits notable strengths in terms of durability and mechanical properties. This study delves into the thermal characteristics of hydration, mechanical behaviour, and failure mechanisms of HBC materials, both with and without fiber admixtures, employing a multifaceted approach encompassing hydration heat experiments, uniaxial compression tests, Brazilian tensile tests, alongside advanced techniques such as acoustic emission (AE) and digital image correlation (DIC). The results indicate that HBC has lower hydration heat release, contributing to a reduction in hydration temperature rise, offering advantages in large-scale structural construction. In terms of strength development, HBC exhibits compressive and tensile strengths similar to PC, while the strength of basalt fiber-reinforced HBC is notably lower than both. In terms of failure modes, both HBC and PC undergo shear failure in uniaxial compression tests, whereas basalt fiber-reinforced HBC experiences splitting failure. In Brazilian tensile tests, HBC and PC exhibit single-direction cracking, while basalt fiber-reinforced HBC shows synchronous cracking at the top, middle, and bottom. Due to the crack-arresting effect of basalt fibers, basalt fiber-reinforced HBC displays a bimodal feature on the stress-strain curve and features a stress plateau on both the stress-strain and strain energy development curves.

Finite element modelling of refractories fracture process zone with gradient enhanced damage models

This study investigates the numerical simulation of fracture behaviour in quasi-brittle materials like magnesia spinel refractories using the Gradient-Enhanced Damage (GED) model. It focuses on the complex modelling of these materials non-linear responses and compares conventional and variant GED models through a wedge splitting test. The results demonstrate that all GED models show a good fit to experimental data. However, the conventional GED model falls short in accurately depicting the fracture process zone. In contrast, the localizing GED model more accurately represents the fracture process zone, limiting spurious damage distribution, but requires finer meshing, elevating computational demands. The stress-based variant reduces spurious damage but is less effective comparatively. The study also assesses the role of heterogeneous strength distribution in replicating realistic crack patterns as observed in experiments.

Effect of raster orientation on pure nylon, carbon fibre nylon, and glass fibre nylon using three-dimensional printing

In this study, pure Nylon 6 is taken for investigation and printed in fused deposition modelling, with short carbon fibre, and short glass fibre as reinforcements. The material behaviour under static and dynamic thermal analysis was measured. The specimens were three-dimensional printed as per ASTM standards, and their mechanical behaviour was analysed. According to the findings, a short carbon fibre-printed specimen results in a maximum tensile strength of about 76% and a flexural strength of 89%. Virgin nylon results in the highest impact properties, showing that adding short fibre reduces the impact strength. The dynamic thermal analysis of virgin nylon, short carbon fibre, and short glass fibre results reveals that carbon fibre nylon increases storage modulus, whereas glass fibre nylon increases loss modulus. The nylon reinforced with short carbon fibre results show improved behaviour under static and dynamic thermal conditions.

A Data-Driven Constitutive Model for 3D Lattice-Structured Material Utilising an Artificial Neural Network

A new data-driven continuum model based on an artificial neural network is developed in this study for a new three-dimensional lattice-structured material design. The model has the capability to capture and predict the nonlinear elastic behaviour of the specific lattice-structured material in the three-dimensional continuum description after being trained through the appropriate dataset. The essential data as the input ingredients of the data-driven model are provided through a hybrid method including experimental and unit-cell level finite element simulations under comprehensive loading scenarios including uniaxial, biaxial, volumetric, and pure shear loading. Furthermore, the lattice-structured samples are also fabricated using SLA additive manufacturing technology and the experimental measurements are performed and used for validation of the model. This then illustrates that the current model/methodology is a robust and powerful numerical tool to conduct the homogenization in complex simulation cases and could be used to accelerate the analysis and optimization during the design process of new lattice-structured materials. The model could also easily be used for other engineered materials by updating the dataset and re-training the ANN model with new data.

From Swiss-cheese to discrete ferroelectric composites: assessing the ferroelectric butterfly shape in polarization loops

We explore the polarization hysteretic behaviour and field-dependent permittivity of ferroelectric-dielectric 2D materials formed by random dispersions of low permittivity inclusions in a ferroelectric matrix, using finite element simulations. We show how the degree of impenetrability of dielectric inclusions plays a substantial role in controlling the coercive field, remnant and saturation polarizations of the homogenized materials. The results highlight the significance of the degree of impenetrability of inclusion in tuning the effective polarization properties of such ferroelectric composites: coercive field drops significantly as percolation threshold is attained and remnant polarization decreases faster than a linear decay.

Implementation of optimal HF welding procedure of steel pipes for high-quality and energy-efficient welds

Electric currents of medium and high frequencies are used for inductive heating and welding of steel products. Furthermore, magnetic concentrators are used for the optimisation of transfer so that they direct the currents at a specific area of the heat-treated steel product. After years of study and detailed experimental research, we have found out that the material behaviour during inductive heat treatment also depends on the type of concentrator applied. The character of the electric current passing through the steel products changes through the application of different concentrators which directly alter the structure and quality of the final product. Ferritic and magneto-dielectric concentrators from different producers have been used in the research with HF inductive welding of steel pipes.

Time-dependent damage development during creep in carbon woven-ply polyphenylene sulfide laminates above the glass transition temperature

In order to understand the coupling between time-dependent behaviours (viscoelasticity, viscoplasticity) and damage mechanisms within carbon woven-ply polyphenylene sulfide (C/PPS) thermoplastic composites subjected to creep loadings at T > Tg (Glass transition temperature), it is necessary to develop experimental protocols adapted to high temperature conditions. To this aim, the present study combines different complementary techniques (acoustic emission, edge replication, fractographic analysis, tomography) allowing in-situ analyses of the damage mechanisms that coexist and interact during the different phases of creep-type loadings. These techniques provide information to quantify and dissociate the different material behaviours (viscoelasticity, viscoplasticity, damage). Two main damage mechanisms are identified: intra-bundle cracking and inter-bundle cracking leading to extensive meta-delamination. Image analyses based on morphological operations allow the evaluation of the surface cracking density (intra- and inter-strand) from edge replicas. At macroscopic scale, the thermo-mechanical response is little influenced by the viscous behaviour of angle-ply C/PSS laminates though their thermo-mechanical behaviour is mainly driven by the PPS matrix. At micro and mesoscopic scales, the results clearly show the onset and propagation of time-dependent damage in C/PPS specimens. By implementing this protocol, the acoustic emission monitoring associated with the quantification of the cracking density proved to be relevant and complementary to study the coupling between viscous effects and damage within C/PPS laminates subjected to high temperature loading.

DLP printed 3D gyroid structure: Mechanical response at meso and macro scale

Rapid prototyping (RP) technology enables the fabrication of complex geometries, making lattice structures increasingly popular. Lattice structures, known as cellular materials, have garnered significant attention over the past two decades due to their ability to optimise mass distribution in components. These structures excel in mechanical properties, catering to energy absorption (bending-dominated structures) and structural performance (stretch-dominated structures). In this paper, we investigate the behaviour of stretch-dominated lattice structures using periodic surface models, specifically focusing on sheet-based Gyroid cells, to allow for a more efficient macroscale modelling. We study cells and scaffolds of different sizes, considering various triply periodic minimal surface thicknesses and relative densities ranging from approximately 0.2 to 0.65. We explore load applications in directions different from the unit cell's principal axes and analyse the strain rate effect on both bulk and cellular material. The lattice structures are manufactured using epoxy resin and digital light processing (DLP) technology. In the range of relative density investigated, both in quasi-static and dynamic conditions, a linear trend is observed for Young's modulus and compression yield strength. To extend the quasi-static results to the dynamic regime, we employ a more generalized normalization technique. This approach divides Young's modulus and compression yield strength by the behaviour of the base material at a specific strain rate, facilitating the correlation of mechanical properties across the two loading regimes. Based on experimental findings, we implemented and calibrated a bi-linear material model for describing, in macroscale, triply periodic minimal surface (TPMS) Gyroid structures. The model coefficients are parameterized with respect to relative density. In addition, the presented material law was compared with that proposed by Gibson-Ashby. Furthermore, we evaluated the anisotropy of both the base material and the unit cell. The first one is done by testing the 3D printed samples in directions different from the printing one, the latter by using the Zener factor. The anisotropy evaluation confirmed the isotropic behaviour of the unit cell within the range of relative density and test conditions investigated. Finally, we perform linear elastic 3D macroscopic and mesoscopic model simulations for combined shear-compression tests using the implemented bi-linear material model and the anisotropic stiffness matrix (obtained through the homogeneous formulation) for the macroscale, and the base material for the mesoscopic one. The results demonstrate the suitability of the proposed equivalent material model for studying the TPMS Gyroid structure in the elastic regime, both in quasi-static and dynamic states. This allows for an efficient FE modelling process of complex lattice structures.

Explicit implementation of hydrogen transport in metals

Hydrogen embrittlement prediction demands a numerical framework coupling a damage model with local hydrogen concentration. The inherent nonlinearity in hydrogen-stress-damage interactions challenges convergence in implicit schemes. To address this limitation, we propose a novel chemical potential-based explicit formulation for simulating hydrogen transport in metals. Our approach exploits a heat transfer analogy, linking mechanical and hydrogen transport via inelastic energy as a heat source. By employing chemical potential rather than lattice concentration, our method eliminates the need for user-defined boundary conditions and hydrostatic stress gradient determination. We integrate a VUMATHT subroutine for diffusion modelling and a VUMAT subroutine for material behaviour, coupling stress and strain rates as a heat source for diffusion. Validating against a classical benchmark, we compare our explicit approach with hydrogen concentration-based methods in ABAQUS Standard and Comsol Multiphysics. Stability conditions are assessed for different mesh sizes and mass scaling densities and the capabilities of our approach are showcased for 3D simulations of notched tensile specimens. Our framework offers a novel and efficient pathway for integrating hydrogen transport with user-defined material behaviour, promising advancements in hydrogen-informed damage models.

Analysis of the integral zeolite molecular sieve process for helium CPS application

Zeolite Molecular Sieves (ZMSs) are commonly adopted in tritium handling facilities for impurity removal from gaseous streams, particularly for tritiated water trapping. Several activities have been conducted to characterize the adsorption and desorption behaviour of the sieving materials. Instead, less attention has been put on the analysis of the integral process comprising the adsorption of the tritiated humidity, the regeneration of the molecular sieve and the recovery of the desorbed water. Focusing on the application for the EU-DEMO helium Coolant Purification System (CPS), this work presents a process simulator relying on a MATLAB dynamic model of the ZMS bed and on a RELAP5/MOD3.3 model for the regeneration loop. The dynamic model can simulate both the adsorption and regeneration modes of the ZMS by providing the temperature and the adsorbate concentration profile along the column, while the thermal-hydraulic model is used to assess the conditions of the regeneration loop. By coupling the outcomes of the two models it is possible to establish the effective regeneration efficiency of the process and the amount of the tritiated water recovered. For the case of helium CPS, the analysis demonstrates the feasibility of the proposed operative scheme and the capabilities of the regeneration procedure to ensure a 74.4 % regeneration efficiency of the ZMS bed.