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The purpose of this paper is to study the effect of the relative density and geometric parameters on the homogenised in-plane elasticity modulus of a cellular honeycomb structure using analytical and numerical approaches.

In this work, the mechanical behaviour of a new design of the honeycomb is analysed through a refined analytical model that is developed based on the energy theorems by considering the shearing and stretching effects in addition to bending.

By taking into account the various deformation mechanisms (MNT), the obtained results show that the values of elasticity modulus are the same for low relative densities, but the difference becomes remarkable for higher densities. Moreover, it is difficult to judge the effect of the relative density and anisotropy of the cellular structure on the values of the homogenised elasticity modulus without considering all the three deformation mechanisms in the analytical model. It is shown that conventional models overestimate the elasticity modulus, especially for high relative densities.

In this paper, a refined model that takes into account the three deformation mechanisms (MNT) is developed to predict the in-plane elasticity modulus of a honeycomb cellular material. It is shown that analytical models that describe the anisotropic behaviour of honeycomb cells can be improved by considering the three deformation mechanisms, which are bending, stretching, and shearing deformations.

To describe the mathematics, mechanics and computer code that are involved in deriving the mechanical properties of a 3D composite material with a complicated internal architecture. To inform the reader how an application programming interface (API) can be used with a commercial FEA code to undertake the task. Finally to validate the process an demonstrate the versatility of the process.

The complex architecture of the composite is imported to an FEA environment and meshed. The special code is written in Pascal that applies six sets of constraints to simulate unit strain vectors on a cell of the composite. After six separate analyses are undertaken, the forces necessary to achieve the boundary constraints are summed to provide stresses and hence the necessary coefficients in the stress to strain relationship for the composite. After global FEA the strains in the homogenized material are used as input to the inverse homogenizer so that stress and strain levels in the individual ingredients of the composite can be calculated for the purposes of assessing failure.

The process of writing separate code to operate in conjunction with a commercial FEA code was found to be very reliable, time‐effective and can be of great benefit to engineers researching with composites.

At this state all the materials can only be stressed within their elastic limit. There is no logical impediment to extending the algorithm to increase stresses into the non‐linear range.

The use of the API environment allows third parties to develop application‐specific code that overcomes the increasing generality of commercial FEA codes. The author can easily make the research available to the whole engineering and materials community without losing any intellectual property.

The practical results of this research are now freely available to the whole community and the work demonstrates in a general way how researchers can make their work available without having to write any FEA code, only the things they have researched.

This paper aims to present a hierarchical multiscale model to evaluate the effect of fused deposition modeling (FDM) process parameters on mechanical properties. Asymptotic homogenization mathematical theory is developed into two scales (micro and macro scales) to compute the effective elastic and shear modulus of the printed parts. Four parameters, namely, raster orientation, layer height, build orientation and porosity are studied.

The representative volume elements (RVEs) are generated by mimicking the microstructure of the printed parts. The RVEs subjected to periodic boundary conditions were solved using finite element. The experimental characterization according to ASTM D638 was conducted to validate the computational modeling results.

The computational model reports reduction (E1, ∼>38%) and (G12, ∼>50%) when porosity increased. The elastic modulus increases (1.31%–47.68%) increasing the orthotropic behavior in parts. Quasi-solids parts (100% infill) possess 10.71% voids. A reduction of 11.5% and 16.5% in elastic modulus with layer height is reported. In total, 45–450 oriented parts were highly orthotropic, and 0–00 parts were strongest. The order of parameters affecting the mechanical properties is porosity > layer height > raster orientation > build orientation.

This study adds value to the state-of-the-art terms of construction of RVEs using slicing software, discarding the necessity of image processing and study of porosity in FDM parts, reporting that the infill density is not the only measure of porosity in these parts.

The main purpose of the paper is to propose a new approach to stochastic computational modeling of interface defects in fiber‐reinforced composites. Interface defects with random radius and total number at the fiber‐matrix interface are modeled as an interphase between original composite components with the thickness obeying all the discontinuities and material parameters of this new, fictitious material are obtained by modified spatial averaging method. Such a model is used in the stochastic finite element analysis of composites in their original configuration. Next, the probabilistic moments of global effective properties of the entire composite are estimated, thanks to the traditional Monte Carlo simulation method implementation. Numerical experiments show that introduction of the interface defects results in significant increase of randomness level of the composite displacements and the homogenized elastic characteristics. Computer programs implemented can find their applications in digital image‐based analysis and the reliability analyses for fiber‐reinforced composites.

This paper aims to establish a multiscale topology optimization method for the optimal design of non-periodic, self-supporting cellular structures subjected to thermo-mechanical loads. The result is a hierarchically complex design that is thermally efficient, mechanically stable and suitable for additive manufacturing (AM).

The proposed method seeks to maximize thermo-mechanical performance at the macroscale in a conceptual design while obtaining maximum shear modulus for each unit cell at the mesoscale. Then, the macroscale performance is re-estimated, and the mesoscale design is updated until the macroscale performance is satisfied.

A two-dimensional Messerschmitt Bolkow Bolhm (MBB) beam withstanding thermo-mechanical load is presented to illustrate the proposed design method. Furthermore, the method is implemented to optimize a three-dimensional injection mold, which is successfully prototyped using 420 stainless steel infiltrated with bronze.

By developing a computationally efficient and manufacturing friendly inverse homogenization approach, the novel multiscale design could generate porous molds which can save up to 30 per cent material compared to their solid counterpart without decreasing thermo-mechanical performance.

This study is a useful tool for the designer in molding industries to reduce the cost of the injection mold and take full advantage of AM.

In this study we examine the spectral properties of stiffness degradation at the constitutive level and at the levels of finite elements and their assemblies. The principal objective is to assess the effects of defects on the elastic stiffness properties at different levels of observation. In particular, we are interested in quantitative damage measures, which characterize the fundamental mode of degradation in the form of elastic damage at the level of constitutive relations and at the level of finite elements and structures.

The purpose of this paper is to present, the global behaviour of sandwich structures comprising cellular cores is predicted by finite element (FE) analysis. Two modelling approaches are investigated, providing different levels of accuracy; in both approaches, the sandwich structure is idealised as a layered stack with the skin modelled using shell elements; while the core is either modelled with fine detail using beam micro-elements representing the cell struts, or is modelled by three-dimensional solid elements after an appropriate core homogenisation.

The applied homogenisation methodology, as well as the all important modelling issues are presented in detail. Experimental tests performed using a mass-drop testing machine are used for the successful validation of the simulation models.

It was concluded that the core microscale models having detailed FE modelling of the core unit cells geometry with fine scale beam elements are suitable for the analysis of the core failure modes and the prediction of the basic core stiffness and strength properties. It was demonstrated that the homogenised core model provides significant advantages with respect to computing time and cost, although they require additional calculations in order to define the homogenised stress-strain curves.

Special microscale material tests are required for the determination of appropriate materials parameters of the core models, as steel selective laser melting (SLM) microstrut properties differ from the constitutive steel material ones, due to the core manufacturing SLM technique. Stress interactions were not taken into account in the homogenisation, as the applied core material model supports the introduction of independent stress-strain curves; however, the predicted load deflection results appeared to be very close to those obtained from the detailed core micromodels.

The paper is original. The dynamic behaviour of conventional sandwich structures comprising conventional honeycomb type cores has been extensively studied, using simple mass-spring models, energy based models, as well as FE models. However, the response of sandwich panels with innovative SLM cellular cores has been limited. In the present paper, novel modelling approaches for the simulation of the structural response of sandwich panels having innovative open lattice cellular cores produced by SLM are investigated.

Traditionally, an armor-grade composite is based on a two-dimensional (2D) architecture of its fiber reinforcements. However, various experimental investigations have shown that armor-grade composites based on 2D-reinforcement architectures tend to display inferior through-the-thickness mechanical properties, compromising their ballistic performance. To overcome this problem, armor-grade composites based on three-dimensional (3D) fiber-reinforcement architectures have recently been investigated experimentally. The paper aims to discuss these issues.

In the present work, continuum-level material models are derived, parameterized and validated for armor-grade composite materials, having four (two 2D and two 3D) prototypical reinforcement architectures based on oriented ultra-high molecular-weight polyethylene fibers. To properly and accurately account for the effect of the reinforcement architecture, the appropriate unit cells (within which the constituent materials and their morphologies are represented explicitly) are constructed and subjected to a series of virtual mechanical tests (VMTs). The results obtained are used within a post-processing analysis to derive and parameterize the corresponding homogenized-material models. One of these models (specifically, the one for 0°/90° cross-collimated fiber architecture) was directly validated by comparing its predictions with the experimental counterparts. The other models are validated by examining their physical soundness and details of their predictions. Lastly, the models are integrated as user-material subroutines, and linked with a commercial finite-element package, in order to carry out a transient non-linear dynamics analysis of ballistic transverse impact of armor-grade composite-material panels with different reinforcement architectures.

The results obtained clearly revealed the role the reinforcement architecture plays in the overall ballistic limit of the armor panel, as well as in its structural and damage/failure response.

To the authors’ knowledge, the present work is the first reported attempt to assess, computationally, the utility and effectiveness of 3D fiber-reinforcement architectures for ballistic-impact applications.

Concrete, the second most used material in the world, surpassed only by water, relies on a vast amount of cement. The process of cement production emits substantial amounts of carbon dioxide (CO₂). Consequently, it is crucial to search for cement alternatives. Geopolymer concrete (GC) uses industrial by-product material instead of traditional cement, which not only reduces CO₂ emissions but also enhances concrete durability. On the other hand, the disposal of concrete waste in the landfills represents a significant environmental challenge, emphasising the urgent need for sustainable solutions. This study aimed to investigate waste concrete's best form and rate as the alternative aggregates in self-compacting and ambient-cured GC to preserve natural resources, reduce construction and demolition waste and decrease pertinent CO₂ emissions. The binding material employed in this research encompasses fly ash, slag, micro fly ash and anhydrous sodium metasilicate as an alkali activator. It also introduces the best treatment method to improve the recycled concrete aggregate (RCA) quality.

A total of25%, 50% and 100% of coarse aggregates are replaced with RCAs to cast self-compacting geopolymer concrete (SCGC) and assess the impact of RCA on the fresh, hardened and water absorption properties of the ambient-cured GC. Geopolymer slurry was used for coating RCAs and the authors examined the effect of one-day and seven-day cured coated RCA. The mechanical properties (compressive strength, splitting tensile strength and modulus of elasticity), rheological properties (slump flow, T500 and J-ring) and total water absorption of RCA-based SCGC were studied. The microstructural and chemical compositions of the concrete mixes were studied by the methods of energy dispersive X-Ray and scanning electron microscopy.

It is evident from the test observations that 100% replacement of natural aggregate with coated RCA using geopolymer slurry containing fly ash, slag, micro fly ash and anhydrous sodium metasilicate cured for one day before mixing enhances the concrete's quality and complies with the flowability requirements. Assessment is based on the fresh and hardened properties of the SCGC with various RCA contents and coating periods. The fresh properties of the mix with a seven-day curing time for coated RCA did not meet the requirements for self-compacting concrete, while this mix demonstrated better compressive strength (31.61 MPa) and modulus of elasticity (15.39 GPa) compared to 29.36 MPa and 9.8 GPa, respectively, for the mix with one-day cured coated RCA. However, incorporating one-day-cured coated RCA in SCGC demonstrated better splitting tensile strength (2.32 MPa) and water absorption (15.16%).

A potential limitation of this study on SCGC with coated RCAs is the focus on the short-term behaviour of this concrete. This limited time frame may not meet the long-term requirements for ensuring the sustained durability of the structures throughout their service life.

This paper highlights the treatment technique of coating RCA with geopolymer slurry for casting SCGC.

The purpose of this paper is to evaluate the efficiency of the fast multipole boundary element method (FMBEM) in the analysis of stress and effective properties of 3D linear elastic structures with cavities. In particular, a comparison between the FMBEM and the finite element method (FEM) is performed in terms of accuracy, model size and computation time.

The developed FMBEM uses eight-node Serendipity boundary elements with numerical integration based on the adaptive subdivision of elements. Multipole and local expansions and translations involve solid harmonics. The proposed model is used to analyse a solid body with two interacting spherical cavities, and to predict the homogenized response of a porous material under linear displacement boundary condition. The FEM results are generated in commercial codes Ansys and MSC Patran/Nastran, and the results are compared in terms of accuracy, model size and execution time. Analytical solutions available in the literature are also considered.

FMBEM and FEM approximate the geometry with similar accuracy and provide similar results. However, FMBEM requires a model size that is smaller by an order of magnitude in terms of the number of degrees of freedom. The problems under consideration can be solved by using FMBEM within the time comparable to the FEM with an iterative solver.

The present results are limited to linear elasticity.

This work is a step towards a comprehensive efficiency evaluation of the FMBEM applied to selected problems of micromechanics, by comparison with the commercial FEM codes.