Search Results (11)

This research work aimed to analyse the impact and potential of cardboard as a construction material, as well as cultural aspects and sustainable construction regulations, in the context of Lima, Peru. The study employed a mixed research methodological approach, including three case studies from Japan, the Netherlands, and the UK, online interviews, and surveys with British, Polish, and Peruvian architects. Additionally, a range of dynamic thermal simulations of an existing school building in the UK employing cardboard construction material were conducted to evaluate its impact on energy consumption. The survey revealed that there is a gap in information about the material applied to the architecture and construction environment, which is coupled with a general distrust and little credibility regarding its inclusion. However, cardboard is also seen as a complementary material in hybrid construction systems, with potential recycling enhancing environmental sustainability. The case studies showed cardboard structures can fulfil different functions with flexible designs that are adaptable to different contexts, simple, economical, accessible, recyclable, and capable of resisting natural disasters. However, post-construction consequences affect the structural integrity. Simulations carried out with EnergyPlus confirmed that cardboard has an optimal performance that can be a great complement or variation to traditional materials to reduce the carbon footprint and could meet the U-value requirements established in the construction regulations. Since it has low thermal conductivity and good acoustic insulation, it is recyclable and generates fewer CO₂ emissions, and it is economical, accessible, versatile, and light in use. For example, from a technical point of view, when used as thermal insulation, this element outperforms other conventional materials due to its cellular structure, which traps air, a poor conductor of heat. This study provides a set of guidelines for sustainable building practices. Such guidelines can be adopted to produce a prototype of a sustainable building using cardboard as the main construction material to contribute to the current debates on the state of building materials. It offers valuable perspectives on the development of building materials, construction techniques, and building regulations that can guide the way forward for sustainable building practices in the future, informing policymakers and building designers about construction techniques that adhere to building codes and lessen the built environment’s environmental impact. Full article

Façades give the first impression of a structure, reflecting the overall aesthetic appeal, architectural styles, cultural influences, and technological advancements. Emphasis on sustainability is increasing, with a shift towards eco-friendly and energy-saving materials, triggered by decreasing the environmental impact of construction. Cork is a green competitive material for various engineering and design applications due to its biological formation, sustainable production and a portfolio of properties including low density, impermeability, viscoelastic behaviour and high thermal insulation that derive from its cellular and chemical features. This work presents cork materials used in building façades and their properties, also giving information on cork production and processing into cork-based products as a review of the existing published research, while also identifying knowledge gaps and further research needed. Historical examples of cladding of constructions with raw cork are given, while the contemporary innovative use of cork façades was triggered by some designs of well-known architects with outdoor application of expanded cork agglomerates. Examples of different historical and contemporary constructions were assembled and critically assessed by the authors. The aim is to give integrated information of cork as a natural, renewable and sustainable material to raise the interest of designers, architects and engineers to explore cork, blending aesthetics with environmental responsibility, targeting a more sustainable and resilient built environment. Full article

The recent literature has introduced the use of architected materials with a metallic lattice structure-based topology to enhance the thermal conductivity of phase change materials (PCM). The potential of such structures lies in the freedom of design with complex geometries. This, however, has introduced novel challenges regarding the analytical description of these materials’ effective thermophysical properties, which are used in order to treat the composite as a homogenized material. Only a few limited works have been presented thus far that have holistically addressed the calculation of such properties. The wide variety of possible geometric parameters in these materials can only be appropriately treated via an adaptable approach that can be extended to upcoming lattice geometries. With this aim in mind, the present work introduces a method to calculate the effective thermal conductivity of the discussed composite PCM. A cell-based approach to calculate the effective thermal conductivity is introduced. The method makes use of Steinmetz’s solids as a basis from which one can derive the porosity of unit cells with variable geometric parameters. Empirical factors are introduced to account for limitations due to the complex geometry and eventual manufacturing imperfections of these structures. Thus, semi-analytical formulae to describe the effective thermal conductivity of the lattice cells are derived for a variety of cuboid and hexagonal prismatic unit cells with generic topological parameters. The formulae are validated against the models and experimental results present in the literature. Finally, an analysis and discussion of the limited validity of homogenization techniques for lattice structures is presented. Full article

Metamaterials are architected cellular materials, also known as lattice materials, that are inspired by nature or human engineering intuition, and provide multifunctional attributes that cannot be achieved by conventional polymeric materials and composites. There has been an increasing interest in the design, fabrication, and testing of polymeric metamaterials due to the recent advances in digital design methods, additive manufacturing techniques, and machine learning algorithms. To this end, the present review assembles a collection of recent research on the design, fabrication and testing of polymeric metamaterials, and it can act as a reference for future engineering applications as it categorizes the mechanical properties of existing polymeric metamaterials from literature. The research within this study reveals there is a need to develop more expedient and straightforward methods for designing metamaterials, similar to the implicitly created TPMS lattices. Additionally, more research on polymeric metamaterials under more complex loading scenarios is required to better understand their behavior. Using the right machine learning algorithms in the additive manufacturing process of metamaterials can alleviate many of the current difficulties, enabling more precise and effective production with product quality. Full article

One of the main advantages of Additive Manufacturing (AM) is the ability to produce topologically optimized parts with high geometric complexity. In this context, a plethora of architected materials was investigated and utilized in order to optimize the 3D design of existing parts, reducing their mass, topology-controlling their mechanical response, and adding remarkable physical properties, such as high porosity and high surface area to volume ratio. Thus, the current re-view has been focused on providing the definition of architected materials and explaining their main physical properties. Furthermore, an up-to-date classification of cellular materials is presented containing all types of lattice structures. In addition, this research summarized the developed methods that enhance the mechanical performance of architected materials. Then, the effective mechanical behavior of the architected materials was investigated and compared through the existing literature. Moreover, commercial applications and potential uses of the architected materials are presented in various industries, such as the aeronautical, automotive, biomechanical, etc. The objectives of this comprehensive review are to provide a detailed map of the existing architected materials and their mechanical behavior, explore innovative techniques for improving them and highlight the comprehensive advantages of topology optimization in industrial applications utilizing additive manufacturing and novel architected materials. Full article

Architected cellular materials encompass a wide range of design and performance possibilities. While there has been significant interest in periodic cellular materials, recent emphasis has included consideration of aperiodicity, most commonly in studies of stochastic and graded cellular materials. This study proposes a classification scheme for aperiodic cellular materials, by first dividing the design domain into three main types: gradation, perturbation, and hybridization. For each of these types, two design decisions are identified: (i) the feature that is to be modified and (ii) the method of its modification. Considerations such as combining different types of aperiodic design methods, and modulating the degree of aperiodicity are also discussed, along with a review of the literature that places each aperiodic design within the classification developed here, as well as summarizing the performance benefits attributed to aperiodic cellular materials over their periodic counterparts. Full article

Three-dimensional printed polymeric lattice structures have recently gained interests in several engineering applications owing to their excellent properties such as low-density, energy absorption, strength-to-weight ratio, and damping performance. Three-dimensional (3D) lattice structure properties are governed by the topology of the microstructure and the base material that can be tailored to meet the application requirement. In this study, the effect of architected structural member geometry and base material on the viscoelastic response of 3D printed lattice structure has been investigated. The simple cubic lattice structures based on plate-, truss-, and shell-type structural members were used to describe the topology of the cellular solid. The proposed lattice structures were fabricated with two materials, i.e., PLA and ABS using the material extrusion (MEX) process. The quasi-static compression response of lattice structures was investigated, and mechanical properties were obtained. Then, the creep, relaxation and cyclic viscoelastic response of the lattice structure were characterized. Both material and topologies were observed to affect the mechanical properties and time-dependent behavior of lattice structure. Plate-based lattices were found to possess highest stiffness, while the highest viscoelastic behavior belongs to shell-based lattices. Among the studied lattice structures, we found that the plate-lattice is the best candidate to use as a creep-resistant LS and shell-based lattice is ideal for damping applications under quasi-static loading conditions. The proposed analysis approach is a step forward toward understanding the viscoelastic tolerance design of lattice structures. Full article

This work focuses on combining digitally architected cellular structures with cementitious mortar incorporating micro-encapsulated phase change material (mPCM) to fabricated lightweight cementitious cellular composites (LCCCs). Voronoi structures with different randomness are designed for the LCCCs. Aided by the indirect 3D printing technique, the LCCCs were prepared with a reference mortar (REF) and a mortar incorporating mPCM. The compressive behavior of the LCCCs was studied at the age of 28 days, by experimental and numerical methods. It was found that the highly randomized Voronoi structure and the mPCM have minor negative influence on the compressive properties of the LCCCs. The mPCM incorporated LCCCs have high relative compressive strength compared to conventional foam concrete. Furthermore, the critical role of air voids defects on the compressive behavior was identified. The highly randomized porous Voronoi structure, high mPCM content and good compressive strength ensure the LCCCs’ great potential as a novel thermal insulation construction material. Full article

The ability to control the exhibited plastic deformation behavior of cellular materials under certain loading conditions can be harnessed to design more reliable and structurally efficient damage-tolerant materials for crashworthiness and protective equipment applications. In this work, a mathematically-based design approach is proposed to program the deformation behavior of cellular materials with minimal surface-based topologies and ductile constituent material by employing the concept of functional grading to control the local relative density of unit cells. To demonstrate the applicability of this design tactic, two examples are presented. Rhombic, and double arrow deformation profiles were programmed as the desired deformation patterns. Grayscale images were used to map the relative density distribution of the cellular material. 316L stainless steel metallic samples were fabricated using the powder bed fusion additive manufacturing technique. Results of compressive tests showed that the designed materials followed the desired programmed deformation behavior. Results of mechanical testing also showed that samples with programmed deformation exhibited higher plateau stress and toughness values as compared to their uniform counterparts while no effect on Young’s modulus was observed. Plateau stress values increased by 8.6% and 13.4% and toughness values increased by 5.6% and 11.2% for the graded-rhombic and graded-arrow patterns, respectively. Results of numerical simulations predicted the exact deformation behavior that was programmed in the samples and that were obtained experimentally. Full article

Expectations and challenges of modern sustainable engineering and architecture stimulate intensive development of structural analysis and design techniques. Designing durable, light and eco-friendly constructions starts at the conceptual stage, where new efficient design and optimization tools need to be implemented. Innovative methods, like topology optimization, become more often a daily practice of engineers and architects in the process of solving more and more demanding up-to-date engineering problems efficiently. Topology optimization is a dynamically developing research area with numerous applications to many research and engineering fields, ranging from the mechanical industry, through civil engineering to architecture. The motivation behind the present study is to make an attempt to broaden the area of topology optimization applications by presenting an original approach regarding the implementation of the multi-domain and multi-material topology optimization to the design and the strengthening/retrofitting of structures. Moreover, the implementation of the design-dependent self-weight loading into the design model is taken into account as a significantly important issue, since it influences the final results of the topology optimization process, especially when considering massive engineering structures. As an optimization tool, the original efficient heuristic algorithm based on Cellular Automata concept is utilized. Full article

In this paper, the superelasticity effects of architected shape memory alloys (SMAs) are focused on by using a multiscale approach. Firstly, a parametric analysis at the cellular level with a series of representative volume elements (RVEs) is carried out to predict the relations between the void fraction, the total stiffness, the hysteresis effect and the mass of the SMAs. The superelasticity effects of the architected SMAs are modeled by the thermomechanical constitutive model proposed by Chemisky et al. 2011. Secondly, the structural responses of the architected SMAs are studied by the multilevel finite element method (FE ${}^2$ ), which uses the effective constitutive behavior of the RVE to represent the behavior of the macroscopic structure. This approach can truly couple the responses of both the RVE level and structural level by the real-time information interactions between two levels. Through a three point bending test, it is observed that the structure inherits the strong nonlinear responses—both the hysteresis effect and the superelasticity—of the architected SMAs at the cellular level. Furthermore, the influence of the void fraction at the RVE level to the materials’ structural responses can be more specifically and directly described, instead of using an RVE to predict at the microscopic level. Thus, this work could be referred to for optimizing the stiffness, the hysteresis effect and the mass of architected SMA structures and extended for possible advanced applications. Full article