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The main purpose of the article is to present the new possibilities of producing natural fiber composite reinforcement. In this case, a computer embroidery machine by ZSK type JCZA 0109-550 was used. A technical embroidery with a stitch length of 2 mm was made on the machine. The embroidery was made of flax roving with a linear density of 400 tex. The woven fabric was made of the same flax roving as the embroidery, with a surface mass of 400 g/m2. Composites were then produced from the technical embroidery and woven fabric using the infusion method with epoxy resin. The individual configurations differed from each other in the orientation of the roving in the embroidery samples. Samples for tensile strength and tensile elongation tests consisted of 4 layers, while samples for the DCB test consisted of 6 layers, with the addition of a separating foil between the 3rd and 4th layer. Composites were then subjected to strength tests - tensile strength, tensile elongation and DCB test (Double Cantilever Beam test), on the INSTRON machine. During the action of force along the direction of the fibers, composites containing technical embroidery as reinforcement were characterized by higher strength than composites containing woven fabric as reinforcement. Additionally, embroidery is a barrier to the formation of interlayer cracks. Technical embroidery is made on the basis of Tailored Fiber Placement (TFP) technology. This technology allows optimizing the mechanical values of the composite reinforcement.

The main purpose of the article is to present the possibilities of producing composite reinforcement with the use of a computer embroidery machine. The study below presents the results of strength tests of composites containing technical embroidery, woven fabric, and UD fabric as the reinforcement. Each of the samples was made of the same material—flax roving. The samples differed from each other in the arrangement of layers in the reinforcement. The composites were made using the infusion method with epoxy resin. The embroidery was made on a ZSK embroidery machine, type JCZA 0109-550. A total of 12 types of composites were produced and tested. The test material was subjected to strength tests—tensile strength, tensile elongation, and shear strength, on the INSTRON machine. As the research showed, the use of technical embroidery as a composite reinforcement increases its tensile strength. Furthermore, the use of embroidery is a vertical reinforcement of the composite and prevents the formation of interlayer cracks. The technology of technical embroidery allows for optimizing the mechanical values of the composite reinforcement.

Natural cork (NC) and its agglomerates are renewable materials that could be effective substitutes for non-renewable foams, such as expanded polystyrene (EPS), in the cores of sandwich materials. Although many existing studies have analysed the behaviour of different cork agglomerates under tensile, compression, or shear loads, no studies to date have simultaneously analysed the behaviour of multiple cork materials under all these loads. Therefore, in this study, the behaviour of NC and five cork agglomerates were analysed under tensile, compression and shear loads, and the mechanical and specific properties and the shape of the stress–strain curves were compared with those obtained for five EPS counterparts to analyse the relationship between the mechanical behaviour of the core and the main failure modes of the sandwich. Although EPS exhibited higher specific properties, NC exhibited higher mechanical properties under all the loads. The agglomerates all exhibited lower mechanical properties except for shear strain. Additionally, because no specific standards were available for testing cork products, slightly modified standards for testing other materials were adopted.

The development of additive manufacturing and lattice structures has created opportunities for the development of lightweight impact–absorption structures that can overcome most constraints of previously used materials such as expanded polystyrene foams. However, for the successful application of such structures, the effects of their variables in their mechanical performance must be established. In this study, the mechanical properties and energy absorption of thermoplastic sheet gyroid structures were investigated and compared with the performance of current materials. Consequently, the specimens were tested after changing the main variables, i.e., cell size and volume fraction, of various thermoplastic materials such as acrylonitrile butadiene styrene, polylactic acid, thermoplastic polyurethane, and polyamide 12. Finally, they were tested in a quasi-static compression test and their deformation stages were photographed. The stress–strain curves of all materials changed after adopting the sheet gyroid structure, exhibiting three distinct regions: linear elastic, long collapse plateau, and densification that made them particularly applicable for energy absorption. Volume fraction affected the layer collapse. The elastic geometrical stiffness increased for higher volume fractions and smaller cells. In addition, the peak and plateau stresses increased at higher volume fractions, and while smaller cells were not directly affected. Additionally, the area under the curves increase with the volume fraction; hence, for most materials, specific energy absorption was larger for higher volume fractions. The constituent material properties contributed significantly to the structural behavior, exhibiting three primary deformation mechanisms, i.e., elastomeric, elastic–plastic, and elastic–brittle, resulting in a wide spectrum of properties for each application requirement. The comparison of the optimal properties with the expanded polystyrene demonstrated the ability of sheet gyroid structures to overcome most of its challenges, exhibiting a superior specific energy absorption, ability to withstand various impacts, letting air flow in its all axes, and being recyclable. Thus, sheet gyroid structures can be considered promising alternatives.

Triply periodic minimal surface (TPMS) structures can produce tailored complex structures for various applications and serve as substitutes for polymeric foams. In this study, six different types of TPMS structures (Neovious, gyroid, Schwarz P, Lidinoid, split P, and diamond) were examined under quasi-static compression in terms of their energy absorption capabilities, mechanical properties, and weights, which were compared with those of expanded polystyrene foam and the original printing material Z-Ultra. It was found that the Neovious, diamond, and Lidinoid structures were most suitable for substituting expanded polystyrene foam, especially in safety helmets requiring high specific energy absorption capabilities.

Additive manufacturing allows the tailoring of the structure of energy-absorbing materials. It is thus feasible now to use light, printed structures instead of other materials such as foams and honeycombs, signifying greater possibilities for customization. Some of these structures are triply periodic minimal-surface structures that is a family of different structures like the gyroid one. Another benefit of additively manufactured graded structures, which foams or honeycombs lack, is the flexibility to vary the internal parameters along one or more directions. This study focuses on the comparative analysis of graded and non-graded gyroid structures for four common thermoplastic materials used in additive manufacturing. These structures are compared with each other under quasi-static compression testing, as well as with expanded polystyrene foam and solid samples of the thermoplastic materials. The analysis includes investigation of the stress–strain and specific stress–strain curves, capability of absorbing energy per unit weight and per unit volume, ideality, total efficiency, and normalized energy vs. normalized stress characteristics. We also analyze the internal fracture mechanism of the structures. The objective is to obtain more extensive knowledge of the behavior of non-graded structures.

As society and regulations demand more ecological materials, we must focus on finding new properties in potential candidates that make them really feasible and open up new possibilities. A new methodology is established to reach that goal, based on already existing ones, but with a broader vision; more focused on the use, and not solely on the product. To put it into practice, it’s been applied on Luffa Cylindrica, a plant with interesting properties. A volumetric, mechanical and perceptual characterization of it has been carried out, so that we can create new concepts specially linked to that. One of these paths has been fully developed to the point of getting a physical prototype, while more complex ones have been suggested. The stated methodology may be used as a flexible guide to find new materials not only more environmentally-friendly, but better than what’s stablished.

Expanded polystyrene foams are a petroleum-origin material that is usually used in some applications such as motorcyclist helmets. Despite it notably mechanical properties, it low density and its capability to absorb energy during an impact, it is necessary to find a renewable-origin substitute material. Thus, it has been studied the use of a sawdust and mycelium composite material under quasi-static and dynamic efforts. Sawdust is a waste material that has very small grains that are totally disaggregated so it has very low material properties. The use of oyster mushroom mycelium generates an internal structure that joins grains and, consequently, the resultant material has notably high mechanical properties. Then it has been compared the resultant properties (stress-strain curve, absorbed energy, decelerations, etc.) with the different densities EPS ones and it has been concluded that this composite material, despite it high density, it could be a suitable substitute material and in some cases it has better properties.

Cork and cork agglomerates could be suitable replacements for petroleum-based polymeric foams due to their similar internal structure of cells and grains. Additionally, cork products have a renewable origin and are recyclable. Despite these notable properties, few studies have analysed the mechanical properties, especially the specific properties, of these materials under compressive loads. Moreover, although efficiency, ideality, and energy-normalized stress diagrams are commonly used for polymeric foams and 3D-printed lattice structures, these types of diagrams are not yet applied to cork products. It must be highlighted that efficiency diagrams are plotted only against nonspecific properties so, this article proposes additionally the use of nonspecific properties to compare materials not only in terms of properties per unit volume instead but also in terms of properties per unit mass that is more suitable for certain applications in which the weight is crucial. The materials studied herein include three different white cork agglomerates, a brown cork agglomerate, a black cork agglomerate, natural cork, and expanded polystyrene foam, which are subjected to quasi-static compressive loads.

Expanded polystyrene (EPS) foam is a material, frequently used in a range of applications for its good energy absorption, thermal insulation, durability, and acoustic absorption. In this wide range of applications, the material undergoes a variety of loads that can extend from static to dynamic. When it comes to crush applications, these loading profiles create the need of well-defined compression and tensile properties for a range of densities and strain rates. Herein, static and dynamic tension tests are conducted on EPS foam dog-bone samples for material characterization. The target of the study is to obtain stress–strain curves for a range of densities spreading from 60 to 120 g L-1. For the low-strain rates, tensile testing machines are used, whereas for the high-strain rates, a modified drop tower set-up is used. The influence of the strain rate on the stress–strain behavior, the dynamic strength, Young''s modulus, and energy absorption capacities for different foam densities is measured. Furthermore, the experimental results for each density are compared with the predictions of Avalle''s model for crushable foams to evaluate the validity of the model. The quality of fit obtained between experimental and theoretical is between 70% and 97% depending on the strain rate.

The interlaminar tensile strength of carbon/epoxy laminated curved beams with variable thickness and through-the-thickness tufted reinforcement is studied experimentally by means of a four-point-be...

MPS (Motorcyclists´ protection systems) play an essential role in the reduction of fatalities and morbidity involved in motorbike and moped accidents, since they offer protection from impact agains...

This article details the analysis of experimental tests regarding the behavior of some vortex generators (VGs) for heavy vehicles. The correlation between numerical and experimental tests, including road tests, smoke and water jet tests, etc. will be highlighted. Two types of vortex generators have been tested, from which high decreases in the drag coefficient in the virtual tests by means of CFD tools were obtained. These vortex generators, are one co-rotational with blade shape VG and the other one with a complex geometry, manufactured by the Air Tab Company. On the other hand, some new low-cost experimental tests have been planned. They do not include the use of a wind tunnel. It has also been necessary to build some functional prototypes of the VGs. It must be highlighted that the use of these types of tests stems from the need to obtain experimental test results to be compared with the numerical results. It must also be pointed out that, due to their high costs, wind tunnel tests have not been conducted to validate the numerical results. However, road test results have proved useful in obtaining the behavior and aerodynamic improvements of the VGs. Keywords: vortex generators, aerodynamic, heavy vehicle, articulated, experimental, trailer.

This study analytically investigates the behaviour of carbon/epoxy laminated curved beams subjected to interlaminar tensile stress by means of a four-point-bending test, carried out in compliance with ASTM D6415 Standard. A Cohesive Zone Model (CZM) has been used to analyse the interlaminar tensile strength (ILTS) and the post-failure behaviour for lay-ups in several thicknesses, as well as the location of first and subsequent predicted delamination. In this study, the model behaviour is described by a bilinear constitutive model. Initially, a law of traction-separation governs the elastic behaviour, until satisfying a quadratic criterion that establishes the failure and degradation starting at the interface. Finally, a law describes the evolution of the damage and the interaction in mixed-mode conditions, which leads to the final failure of the interface and delamination onset. Two-dimensional finite element models (FEM) have been created to apply the CZM and analyse the influence of several cohesive model parameters, such as, cohesive element stiffness, cohesive element size and critical energy release rate. Predicted load–displacement curves have been compared with the experimental results obtained and strong correlation has been observed. The ILTS values predicted by the two-dimensional models show deviations no greater than 5.6% in comparison with the experimental results. These models and the influence of their parameters play an important role in the prediction of the interlaminar tensile strength and the post-failure behaviour of laminated curved beams.

The interlaminar tensile strength of carbon/epoxy laminated curved beams with variable thicknesses is experimentally studied by means of a four-point-bending test. Firstly, the relationships between the used formulae and the results obtained are analyzed on the curved beams with different thicknesses and tested in compliance with ASTM D6415 standard. Secondly, both the interlaminar tensile stresses and the post-failure behaviour are determined. Finally, the critical area, where delamination begins, is reinforced through-the-thickness by means of tufting technology with different densities. The influence on the maximum interlaminar tensile stress as well as delamination evolution of the carbon/epoxy laminated curved beams are analyzed. These results play an important role in the prediction of interlaminar tensile strength and post failure behaviour of laminated curved beams.

El objetivo de este artículo es reflejar la metodología utilizada para la mejora de una asignatura del Espacio Europeo de Educación Superior (EEES) utilizando diversas herramientas de mejora continua, basado en el Kaizen. La mejora continua es una herramienta de trabajo especialmente conocida dentro del ámbito de la ingeniería, principalmente para la mejora de procesos y productos, pero que puede utilizarse en cualquier proceso de mejora. Concretamente, se han utilizado dos herramientas de esta metodología: el DAFO para el análisis de debilidades, amenazas, fortalezas y oportunidades y, a partir de los resultados obtenidos, se plantean diversas acciones con el objetivo corregir las debilidades, afrontar las amenazas, mantener las fortalezas y explotar las oportunidades, mediante lo que se conoce como herramienta CAME. Todo ello se ha implementado para la mejora del proceso de enseñanza-aprendizaje en la asignatura Expresión Gráfica II (EGII) del Grado de Ingeniería de Diseño Industrial y Desarrollo de Producto (IDIDP) de la Universidad de Zaragoza (UZ) [The aim of this paper is to show the use of a methodology to improve a subject of the Superior European Education Space based on the use of diverse tools of the continuous improvement system, based on the Kaizen. The continuous improvement system is a tool specially used in the engineering sector to improve industrial process and products, but that can be used in any improvement process. Concretely, it has been used two tools: the SWOT and the CAME analysis that are complementary. The SWOT tool allows to determine the strengths and the weakness and to identify the opportunities and the threats. On the other hand, the CAME tool allows correcting the Weaknesses, adapting to and adjusting to the threats, maintaining the strengths and exploring the opportunities. These tools have been used to improve the teaching and the learning process in the subject Graphical Expression II of degree of Industrial Design and Product Development Engineering of the University of Zaragoza.]

A general theory of elasticity-based finite element formulation applied to the free edge effect is described in this paper. The F.E. error estimation is also addressed. Optimum mesh criteria based on the even distribution of global and specific error are shown. This technique has been applied to a [±25°/90°] s T300/934 laminate. Four different numerical models have been compared in terms of through-thickness tensile and shear interlaminar stresses, with varying degrees of complexity and yielding various degrees of error. As a result of this study, a reliable numerical model with a low level of error has been obtained. Finally, a theory–experiment correlation study has been carried out over a (+45°, −45°, 0°) s laminate loaded in tension. Both, strain-to-failure and failure mode were successfully correlated.

The aim of this article is to introduce a structural optimization tool based on the combination of neural networks and genetic algorithms, applied to optimize a cryogenic tanker vehicle. To use this tool, it is necessary to introduce an equation that defines the aspects that are going to be optimized (weight, resistance, rigidity, etc.) of a part of the vehicle (the parking zone). Sometimes, this equation is difficult or impossible to model mathematically and then the neuronal networks allow approaching this equation from some particular solutions of the equation and then we will be able to find the solution at any point in the search space on the basis of a set of values of different solutions to the equation. For the tanker vehicle, the neuronal network is used to know the maximum Von Mises stress that is impossible to model mathematically. The genetic algorithms are used to optimize the equation and allow knowing the optimal design of the vehicle tanker. The symbiosis of both techniques are very useful...

The objective of this paper is the simulation of some different types of elements for semitrailers, like the suspension, both mechanical with springs and pneumatic with a spring anddiapresses; other parts like the wheels, the torsion bars, the fifth wheel and the suspension of the tractor unit have also been simulated. Then, the numerical simplified FE model of these elements that allows simulating the real behavior of the suspension to apply adequately the boundary conditions of a heavy vehicle has been obtained for a structural simulation using numerical tools with a good accuracy of the local and global behavior of the vehicle.

The goal of this paper is the development of a design methodology, based on the use of finite elements numerical tools and dummies in order to study the damages and injuries that appear during a motorcyclist collision against a motorcyclist protection system (MPS). According to the existing regulation, a Hybrid III dummy FEM model has been used as a starting point and some modifications have been included. For instance a new finite element helmet model has been developed and later added to the dummy model. Moreover, some structural elements affecting the simulation results such as the connecting bolts or the ground have been adequately modeled. Finally there have been analyzed diverse types of current motorcyclists protection systems, for which it has been made a comparative numerical-experiment analysis to validate the numerical results and the methodology used.

The tipping operation of a dump semi-trailer increases the vehicle rollover risk. A higher centre of gravity, a transversal slope, varying compression degrees of the ground or an irregular unloading can lead to non-desirable lateral instability situations. Therefore it is interesting to analyse the torsional rigidity of the semi-trailer dump bed under unfavourable load conditions generating torsional compliance. By means of detailed finite element models, it has been possible to verify the correct performance of the articulated coupling between the semi-trailer dump bed and the hydraulic actuator in the presence of any unfavourable stability conditions that could occur.

A methodology for validating a three-axle semi-trailer finite element model has been proposed in the present paper. This methodology is based on the establishment of a strong correlation between natural frequencies and mode shapes obtained by means of two different procedures: FEM modal analysis and impact hammer modal testing. The application of this methodology to the specific typology of vehicle analysed, coupled with the large size of its frame, and the development of the experimental analysis in situ at the assembly line during the manufacturing process, constitutes the main novelty and contribution of this paper. Moreover, it was necessary to develop a detailed finite element numerical model of the semi-trailer frame in order to achieve the best numerical-experimental correlation.

The aim of this paper is the aerodynamic study of the use of Vortex Generators (VGs) in some zones of a heavy vehicle (the gap between the cab and the trailer and the rear part of the trailer) using computational fluid dynamic methodology to compare their behaviour in some zones with themselves and with the model without them, analysing the drag forces, the fuel efficiency and the aerodynamic behaviour of the vehicle, because the fuel efficiency and the economic study are essential aspects that have a high influence in heavy vehicles.

The aim of this paper is the aerodynamic study of the use of boat tails to reduce the aerodynamic drag coefficient in heavy vehicles. There are some improvements and some patents that improve the aerodynamic efficiency of the vehicle and the fuel consumption, but there are no experimental or numerical analyses of this benefit. This paper analyses some of these improvements using numerical tools and comparing the results with the results of the vehicle without them. To make the numerical analysis, the CFD methodology, using FLUENT, has been used since it allows simulating some geometries and modifications of the geometry.

The aim of this article is to present a methodology for calculating vehicle tankers by analysing the way baffle shape contributes to the movement of the fluid. This methodology could be used to optimise the geometry of these parts analysing different geometries. Four different lateral types of baffles used by different cryogenic tank manufacturers have been examined. Both the movement of the fluid and the forces transmitted by the latter to the tank during emergency braking manoeuvres are analysed and the principal conclusion is that the contribution of the geometry is very important. Besides, a longitudinal baffle meant to reduce the tendency of the tank to overturn while diminishing the moment generated by the load has been designed. The longitudinal baffle has been optimised, modifying the height and depending on the level of filling of the tanker the rollover moment can be reduced.

The European legislation for rear underrun protection systems on heavy vehicles, Commission Directive 2006/20/EC, specifies a series of criteria that must be fulfilled so that these devices can be homologated. The different models of devices used as rear underrun impact protection in tank vehicles for fuel transportation are an example of these criteria. Basically, the homologation tests based on this regulation consist in the quasi-static application of a load series at different points of the structure. In analysing the guidelines of Commission Directive 2006/20/EC, a number of questions about their validity may be raised with respect to, for instance, how efficient a homologated system of these characteristics is in real collision. The aim of this paper is to compare the behaviour of a rear underrun impact protection system, incorporated into a tank vehicle, to the behaviour of the same device when a car hits it at different collision speeds.