Prof. Dr.-Ing. Götz T. Gresser

Abstract

A continuously adjustable façade shading system functionalized with photovoltaics enables, besides adaptive shading, energy harvesting by solar tracking. This requires large bending motion in two directions. In this paper, the development of an appropriate façade module – FlectoSol – is presented. To achieve motion of ±80°, first time two pneumatic actuators are integrated into a GFRP-elastomer hybrid composite. To improve energy efficiency resp. air pressure consumption of actuation without impairing shading, a parametric study is performed. In detail the influencing criteria of the bending motion “overlap of the actuators” resp. “stiffness ratio of the actuator-surrounding GFRP” and their effect on the target parameters “bending angle”, “shadow width” resp. “air pressure consumption” are analyzed. It could be stated that the “stiffness ratio” only effects the air pressure consumption, but the “overlap” also effects the shadow width. The bending angle itself is, up to ±80°, only limited by the absolute laminate stiffness.

Abstract

Fiber-reinforced composites offer innovative solutions for architectural applications with high strength and low weight. Coreless filament winding extends industrial processes, reduces formwork, and allows for tailoring of fiber layups to specific requirements. A previously developed computational co-design framework for coreless filament winding is extended toward the integration of reciprocal design feedback to maximize design flexibility and inform design decisions throughout the process. A multi-scalar design representation is introduced, representing fiber structures at different levels of detail to generate feedback between computational design, engineering, and fabrication. Design methods for global, component, and material systems are outlined and feedback generation is explained. Structural and fabrication feedback are classified, and their integration is described in detail. This paper demonstrates how reciprocal feedback allows for co-evolution of domains of expertise and extends the existing co-design framework toward design problems. The developed methods are shown in two case studies at a global and component scale.

Abstract

Climate change necessitates exploring innovative geoengineering solutions to mitigate its effects---one such solution is deploying planetary sunshade satellites at Sun--Earth Lagrange point 1 to regulate solar radiation on Earth directly. However, such long-span space structures present unique technical challenges, particularly structural scalability, on-orbit manufacturing, and in-situ resource utilization. This paper proposes a structural concept for the sunshade's foil support system and derives from that a component-level modular system for long-span fiber composite lightweight trusses using coreless filament winding. Within a laboratory-scale case study, the component scalability, as well as the manufacturing and material impacts, were experimentally investigated by bending deflection testing. Based on these experimental results, FE models of the proposed structural concept were calibrated to estimate the maximum displacement and mass of the foil support structure, while comparing the influences of foil edge length, orbital load case, and material selection.

Abstract

As a result of the recent increase in the need for silicon in solar panels, thin-film photovoltaic modules have the capacity to substantially penetrate the market. Thin-film technologies for photovoltaic, as a viable alternative for special implementation as presented in this project, have the potential to deliver a good performance. Due to the integration of photovoltaic on solar shading products unconsidered areas can be used for energy harvesting and has an positive influence for the total energy. The adaptability of thin-film cells opens up numerous application possibilities, especially in terms of surface cladding, as it can be considered a slim layer and does not require a costly metal structure for installation. A thin-film photovoltaic implementation on adaptive shading products is presented in this paper on a demonstrator building in Freiburg. The aim of this work is to give an overview of different thin-film solar cell technologies for applying on solar shading products as well as profitability investigation of such technologies.

Abstract

The linear design workflow for structural systems, involving a multitude of iterative loops and specialists, obstructs disruptive innovations. During design iterations, vast amounts of data in different reference systems, origins, and significance are generated. This data is often not directly comparable or is not collected at all, which implies a great unused potential for advancements in the process. In this paper, a novel workflow to process and analyze the data sets in a unified reference frame is proposed. From this, differently sophisticated iteration loops can be derived. The developed methods are presented within a case study using coreless filament winding as an exemplary fabrication process within an architectural context. This additive manufacturing process, using fiber-reinforced plastics, exhibits great potential for efficient structures when its intrinsic parameter variations can be minimized. The presented method aims to make data sets comparable by identifying the steps each data set needs to undergo (acquisition, pre-processing, mapping, post-processing, analysis, and evaluation). These processes are imperative to provide the means to find domain interrelations, which in the future can provide quantitative results that will help to inform the design process, making it more reliable, and allowing for the reduction of safety factors. The results of the case study demonstrate the data set processes, proving the necessity of these methods for the comprehensive inter-domain data comparison.

Abstract

Adaptive façades can greatly impact a building's energy balance by responding to external climates and by regulating internal conditions. With the integration of solar energy harvesting components, they have the potential not only to reduce the energy loss of buildings but also to gain energy. This premise has been tested within the framework of bio-inspired compliant mechanisms for adaptive façade elements, developed at the University of Stuttgart. Due to the flexible kinematic behavior of bio-inspired adaptive architectural elements, an innovative and simple alternative to common, more complex applications of adaptive façade components is obtained. The research presented aims at establishing the environmental criteria that will lead to an improved energy performance of a building using elastically deformable, adaptive faҫade elements with integrated photovoltaics. Through simulations and physical testing, the influence of daylight, solar radiation, and the building´s thermal balance are evaluated. The findings of this research are showcased on an adaptive façade consisting of pneumatically actuated, glass fiber-reinforced plastic laminates with integrated photovoltaics, assembled at Botanical Garden in Freiburg, Germany. Relying on environmental sensing, this façade is able to adapt over time in response to solar conditions with the goal of finding the right balance between low-energy building operation, high indoor environmental quality, and high energy harvesting. This study provides a novel, integrative design method utilizing adaptive building envelopes that successfully react to varying environmental conditions in an energy-efficient and cost-effective manner.

Abstract

Despite all current efforts, climate change is the greatest challenge of the 21st century. Since existing measures will fail to prevent critical tipping points from being reached, in addition to terrestrial geoengineering methods, efforts are underway to explore new ways to implement space-based geoengineering methods into the short-term construction of a buffer solution - the International Planetary Sunshade (IPSS). The IPSS system reduces solar irradiation mitigating the global mean temperature rise while offering a sustainable energy supply. The developement of the system poses multifaceted challenges only to be mastered by a collaboration of space agencies and private companies, while supported by society. Therefore, tackling the IPSS within international roadmaps is essential to exploit synergies, shorten development time, and promote international cooperation. An evolutionary concept achieves stepwise Earth independence by utilizing lunar resources. The feasibility of the IPSS also depends on the foil’s supporting structure. Therefore, a lightweight manufacturing technology that meets several criteria, such as scalability, adaptivity, material compatibility, full automation, on-orbit manufacturing, in-situ resource utilization, and digital design including function integration, must be adopted. Hence, coreless filament winding (CFW) may be a suitable technology for realizing the demanded mass savings. The prerequisite for the superiority of CFW structures is an application- and material-compliant component and fiber net design. Previous experience with CFW cannot be directly transferred to the IPSS system due to the changed requirements for space application. This paper will present a systematic design concept for the IPSS, initially exploring a CFW support structure by discussing segmentation and modularity, proposing a new connection system, and implementing function integration.

Abstract

Photovoltaik (PV) spielt im Ausbau eines CO2-freien Energiesystems eine zentrale Rolle, dabei können durch die Integration von PV in Sonnenschutzsystemen bisher unbedachte Flächen für die Energiewende aktiviert werden. Ein Lösungsansatz sind PV-integrierte Sonnenschutzsysteme, beispielsweise adaptive Fassadenelemente aus faserverstärktem Kunststoff (FVK) und applizierten PV-Modulen. Die PV-Integration führt jedoch zu großen Herausforderungen in der übergeordneten Gebäudesteuerung, da im Steuerungskonzept für solche Sonnenschutzsysteme eine gesamtheitliche Lösung berücksichtigt werden muss. Die zentralen Aufgaben dieses Steuerungskonzeptes sind die Regulierung des Tageslichteintrages in den Raum und gleichzeitig die Verhinderung von Blendung, die energetische Wirkung auf das Gebäude sowie den PV-Ertrag im Zeitschritt zu maximieren. In dieser Arbeit wird ein Steuerungskonzept vorgestellt, bei dem auf Basis einer modellbasierenden Evaluierung mit einer Software Steuerungsfunktionen abgeleitet und in eine bestehende Gebäudesteuerung integriert werden.

Abstract

Mineral cast, also referred to as polymer concrete, is a type of composite material commonly used in the construction of machine tools. It consists of mineral fillers and a thermosetting matrix and is used as an alternative to grey cast iron due to its improved damping properties, lower thermal expansion and density. However, due to its poor tensile and bending properties, it is not suitable for use in load-bearing or moving machine components. In order to open up such components as further application possibilities and to be able to use the advantages of mineral cast, the tensile properties must be improved. In order to achieve the durable bearing of tensile loads, prestressed carbon fibre reinforcements are investigated. The presented research aims to enhance the tensile properties of mineral cast through the integration of pre-stressed carbon fibre reinforcements. The study investigates the suitability of using rovings in contrast to pultruded rods for this application. The adhesion of the reinforcement within the mineral cast is evaluated with pull-out tests, and the impregnation behavior of prestressed rovings in the mineral cast is examined through micrographs. Results from the tests indicate that the pull-out forces of rovings are more than 200 \% higher than those of comparable rods with the same fibre content. However, prior consolidation of the rovings is necessary for complete impregnation.

Abstract

Coreless filament winding is a manufacturing process used for fiber-reinforced composites, resulting in high-performance lightweight lattice structures. Load transmission elements, which are assembled from commercially available standardized parts, often restrict the component design. A novel adaptive winding pin was developed, which is made by additive manufacturing and can therefore be adjusted to specific load conditions resulting from its position within the component. This allows to decouple the fiber arrangement from the winding pin orientation, which allows a fully volumetric framework design of components. A predictive model for the pin capacity was derived and experimentality validated. The hooking conditions, pin capacity, and occupancy were considered in the creation of a digital design tool.

Abstract

Digitization and automation are essential tools to increase productivity and close significant added-value deficits in the building industry. Additive manufacturing (AM) is a process that promises to impact all aspects of building construction profoundly. Of special interest in AM is an in-depth understanding of material systems based on their isotropic or anisotropic properties. The presented research focuses on fiber-reinforced polymers, with anisotropic mechanical properties ideally suited for AM applications that include tailored structural reinforcement. This article presents a cyber-physical manufacturing process that enhances existing robotic coreless Filament Winding (FW) methods for glass and carbon fiber-reinforced polymers. Our main contribution is the complete characterization of a feedback-based, sensor-informed application for process monitoring and fabrication data acquisition and analysis. The proposed AM method is verified through the fabrication of a large-scale demonstrator. The main finding is that implementing AM in construction through cyber-physical robotic coreless FW leads to more autonomous prefabrication processes and unlocks upscaling potential. Overall, we conclude that material-system-aware communication and control are essential for the efficient automation and design of fiber-reinforced polymers in future construction.

Abstract

The manufacturing process of robotic coreless filament winding has great potential for efficient material usage and automation for long-span lightweight construction applications. Design methods and quality control rely on an adequate digital representation of the fabrication parameters. The most influencing parameters are related to the resin impregnation of the fibers and the applied fiber tension during winding. The end-effector developed in this study allows efficient resin impregnation, which is controlled online by monitoring the induced fiber tension. The textile equipment was fully integrated into an upscaled nine-axis robotic winding setup. The cyber-physical fabrication method was verified with an application-oriented large-scale proof-of-concept demonstrator. From the subsequent analysis of the obtained datasets, a characteristic pattern in the winding process parameters was identified.

Abstract

A hemispherical research demonstration pavilion was presented to the public from April to October 2019. It was the first large-scale lightweight dome with a supporting roof structure primarily made of carbon- and glass-fiber-reinforced composites, fabricated by robotic coreless filament winding. We conducted monitoring to ascertain the sturdiness of the fiber composite material of the supporting structure over the course of 130 days. This paper presents the methods and results of on-site monitoring as well as laboratory inspections. The thermal behavior of the pavilion was characterized, the color change of the matrix was quantified, and the inner composition of the coreless wound structures was investigated. This validated the structural design and revealed that the surface temperatures of the carbon fibers do not exceed the guideline values of flat, black façades and that UV absorbers need to be improved for such applications.

Abstract

Adaptive shading devices are of special interest in the context of global need for reducing greenhouse gas emissions. To reduce mechanical complexity of kinetic architectural applications, the investigation of bio-inspired compliant mechanisms has proven to be a promising approach. Thus, a coherent integrative design framework for bio-inspired kinetic folding mechanisms has been developed. This includes the abstraction process of biological principles, such as kinematic behaviours, actuation, as well as materialisation principles. A computational design and simulation model is built to analyse the kinematic and kinetic behaviour of the abstracted biological principles under consideration of specific materialisation and fabrication parameters and constraints. The design and simulation model builds the basis for an automated fabrication process, as well as for interaction and active control of the physical application. The development of the ITECH Research Demonstrator 2018-19, a large-scale compliant folding mechanism, inspired by the folding behaviour ladybug wings (Coleptera coccinellidae), serves as a case study of the developed process. The folding motion of the demonstrator is facilitated by distinct elastic hinge-zones with integrated pneumatic actuators.

Abstract

Regarding modern, daylight-flooded buildings with large window façades, appropriate shading systems to improve the energy consumption of climate controlling systems are becoming more relevant. Building envelopes contribute largely to the temperature control and should be at best installed on the outside to prevent the interior from heating up. Preferably, those systems work with minimum maintenance and maximum robustness, covering as much of the window area as possible. Previous shading systems were mostly based on rigid-body mechanisms using error-prone joints. Components, whose movability is achieved by a local compliance of the material, offer a way to avoid the usage of mechanical joints. Within this paper, a new fiber-reinforced plastic (FRP) façade shading demonstrator called “Flexafold” is presented. Its opening and closing movement are controlled by pneumatic cushions which are integrated directly into the laminate set-up. The Flexafold shows thereby the possibility of producing self‑supporting, adaptive FRP components whose actuators are integrated into the component and thus protected in exterior applications. The functional principles and components of Flexafold, e.g. the locally compliant FRP material, the folding pattern and the integrated actuator system, are explained within this paper. Furthermore, a comparison to existing adaptive façade shading systems “flectofin®” and “Flectofold” is given.

Abstract

Bridges and roofs are often supported by branched steel columns. Their production is usually expensive and consumes a great deal of energy. In nature, plants manage to form similarly strong and frequently even more complex branch systems through natural growth processes. They can effortlessly withstand mechanical loads, such as their own weight, wind pressure, snow load, or the heavy weight of fruit. In order to find out about the success strategies of ramified trees and shrubs and to learn from them for architecture, we need more than a detailed look at the form of ramification and inside the plants. We also need computer models and new materials and methods for the production of branched support structures in building construction to succeed in transferring the biological concepts to technology.

Abstract

Natural structural systems that have developed over millions of years illustrate how large loads can be absorbed with very little material. This is achieved by adapting the structural properties to a predominant load profile. If we succeeded in transferring these principles to structures created by people, it would be possible to significantly reduce the consumption of resources in the construction industry. As a contribution to this, the Rosenstein Pavilion was developed based on bio-inspired optimization strategies in order to demonstrate the potential of resource-efficient building.

Abstract

Compliant mechanisms of fiber-reinforced plastic (FRP) have been developed to reduce the mechanical complexity of kinetic systems. In a further step, pneumatic actuation was integrated into the set-up of the FRP, offering lightweight, slender, and inconspicuous actuation. Inflation of an integrated cushion causes rotation through the asymmetric material lay-up. Inspiration from the ultrastructure of pressurized veins in arthropod wings has led to the development of a thin layer of elastomer surrounding this pneumatic cushion to avoid delamination. T-peel tests revealed that the elastomer forms a higher adhesion to itself than to glass-fiber-reinforced plastic (GFRP) layers with an epoxy matrix. The angle-pressure relationship for specific GFRP samples with a defined compliant hinge zone was investigated physically and numerically, showing good consistency between the two. Further, a mathematical model, taking into account the bending stiffness of the cushion-surrounding FRP layers, was developed, and a parametric study was conducted on the actuation angles.

Abstract

Biology can provide exciting ideas for the development or improvement of technical products. As a rule, the underlying principles are first investigated using a feasibility demonstrator, which does not represent a finished technical product but nevertheless, on the whole, is intended to “function” like the finished product. However, there is a long way to go from this first prototype to a product that is ready to use or to a convincing building method. In this process, numerous ideas that at first seem interesting and promising have to be abandoned. Many aspects must be investigated in parallel, and plausible solutions need to be found, not only in terms of reliable and durable functionality, but also in terms of commercial viability and resource-efficient manufacture. In addition, it is important that an innovative product is accepted in the market. In the case of architecture, this means-above all- that the product is esthetically appealing, because without that aspect, there will not be much interest even if the product functions well.

Abstract

Plants have neither muscles nor “classic” local joints-and yet they can move. In the course of evolution, efficient movement mechanisms and esthetic movement forms have developed. Architects and engineers, in cooperation with biomechanists, are benefiting from this botanical “offering” and drawing inspiration for the development of new types of facade shading systems for modern buildings.

Abstract

Nature creates efficient, complex structures using the smallest possible amount of material. The construction principles employed and the intelligent use of materials regarding their specific properties can be transferred to modern production methods. The objective is to produce functional low-weight building components that consume as few resources as possible. In this chapter we show how this bionic transfer takes place by continuing the development of production methods, such as fiber technology (pultrusion, fiber deposition), 3D printing, the manufacture of concrete components, and a combination of these three methods.

Abstract

Within the collaborative research center Biological Design and Integrative Structures (CRC TRR 141), a research team of biologists, architects and engineers from Freiburg, Tübingen and Stuttgart is working on the development of biomimetic and bioinspired structures for implementation in architecture and building construction. One of the projects in this research center deals with the kinematics of planar, curved and corrugated plant surfaces as concept generators for deployable systems in architecture. It is an example for methods of engineering science at the interface between biology and architecture. The contribution will provide an insight into the process of analyzing the waterwheel plant Aldrovanda vesiculosa, a carnivorous plant that catches its prey by a quick closing movement of a snap trap consisting of two lobes attached to a midrib. At a first glance, the mechanism resembles the one of the famous Venus flytrap; however, it appears to be quite different from a mechanical point of view. In fact, a key aspect in the research presented here is the development of mechanical models and performing corresponding finite element analyses of the plant with the aim to obtain a better understanding of the compliant mechanism of Aldrovanda vesiculosa and its actuation. The latter is related to a change in turgor pressure in a so-called motor zone, adjacent to the midrib, possibly combined with prestressing effects. Apart from this scientific contribution to technical biology or reverse biomimetics, the abstraction of the trapping movement and its implementation in a façade element (Flectofold) as an example of biomimetic architectural design are briefly described.

Abstract

Based on a textile technology known from carpet manufacturing (tufting) respectively z reinforcement of fibre-reinforced plastics (FRPs), a new process has been developed for interface connections between two FRP component parts: tufting of pre-fabricated FRP pins during preform manufacturing. Both preform and tufting loops are impregnated simultaneously. Afterwards so called "tufting pins" protrude out of plane of the FRP plate or into the inside of a 3D FRP hollow structure, for example a cylindrical component. The hollow structure can be filled with a core material in particular to enhance mechanical properties. In the case of micro-gaps caused e. g. by shrinkage of the material the pins close these micro-gaps between core and FRP-hull or rather maintain mechanical contact between hull and core. In extensive tests the general adhesion properties between pinned FRP and concrete as a filling material as well as the influencing variables of the tufting process with regard to their effects on mechanical parameters were investigated. Decisive influencing factors result both from the textile process as well as the component design. It is shown, how the tension load of a tufted FRP connection increases depending on the reinforcing fibre material as well as the number of tufting pins.

Abstract

Within the collaborative research center Transregio 141 ‘Biological Design and Integrative Structures. Analysis, Simulation and Implementation in Architecture’, the authors work in an interdisciplinary team composed of biologists, structural engineers, and textile engineers developing novel technical branchings as structural elements for architecture inspired by branchings in nature. Branchings are common in structures of plants and construction and have to fulfill structural demands in both fields. As resource efficiency is a vital factor allowing plants to resist competitive stress, beneficial load-bearing principles found in plants might, in an abstracted manner, also improve technical support constructions. To discover these principles, the biomechanics of selected plant branchings were investigated by FE-simulations. The observed principle of continuous fiber courses from the stem into the branch yields stiff and strong connections also favored in artificial joints. The key challenge is to produce technical branchings with a continuous fiber arrangement. This is enabled by a newly developed braiding process for branched structures. The design of the branched large-scale demonstrator at the Museum of Natural History in Stuttgart for the exhibition ‘baubionik’ (construction-bionics) reveals the potential for future architectural applications with individually variable knot geometries. The findings of the investigation mark a starting point for a novel braided concrete-fiber-reinforced plastic composite construction for branched supporting columns with both high aesthetical and load-bearing demands as a potential competitor for current construction methods of cast steel knots or labor-intensive welded steel pipe joints.

Abstract

Measurement devices such as sweating manikins, cylinders or hotplates are used for testing thermal and moisture transfer properties of clothing or textiles. A critical feature of these measurement devices is the design of the outer covering fabric that tightly enfolds the device like a skin. The artificial skin principally has to match individual requirements because the different sweating devices have different sweating systems and surface compositions. In this study knitted fabrics with different fiber and yarn types are proposed to be used as an artificial skin. Thermal and moisture properties of the fabrics were measured to obtain skin-like characteristics and a mathematical model for the quantification of thermal and moisture-management properties based on geometrical characteristics was developed. The results show that the thermal and moisture-management properties of the fabrics do not only depend on the fiber properties but also relevantly on their geometrical properties such as thickness, diameter and number of stitch pores. For example, thermal resistance is significantly affected by the stitch pore diameter, and evaporative resistance by the fabric thickness. Furthermore, water content and drying speed are determined by the capillary structure, and therefore, are more influenced by yarn and fabric structure parameters, whereas contact angle and wettability are more influenced by the fiber type. In conclusion, the tested fabrics satisfy all the requirements to match the anatomical properties of the human skin; however, two fabric types, PES_19f30_SET and PES_28f48_GL, exhibited superior characteristics suitable for application as artificial skin on measurement devices.

Abstract

Fiber-reinforced materials offer a large improvement in structural performance if specific load cases can be determined. In aerospace, lightweight structures are crucial because of launcher limitations. For academic purpose CubeSats are a powerful concept to participate in space research on a low-cost-level. Reducing the structural mass, while keeping the mechanical performance, provides a bigger payload mass budget. Additionally, there are several types of payloads that do not fit in common structural components. Inasmuch as CubeSats are mainly used in research, such systems change substantially, so that an easily adaptive method would be beneficial to be no longer restricted by prefabricated structural components. The developed rapid prototyping technology tackles these issues by having an automated 3D deposi- tion method which can produce extremely lightweight as well as geometrical- and load-adaptive primary structures with minimum space requirements. A fiber deposition head for a six-axis robot has been devel- oped to impregnate and wind a single carbon roving on a frame to produce 3D integral components. The geometry of the frame can be adjusted to the required application by introducing holes or attachment points at nearly any position. Its modular layout varies, so that it only can be fabricated economically by fused deposition modeling and removed after resin curing easily. Furthermore, by blending additives into the resin it is possible to create material gradient components. Hence adaptiveness can be generated e.g. in terms of solar energy absorption. Compared with 1U aluminum wall structures available on market a carbon fiber-reinforced plastics (CFRP) winded structure results in a mass saving of 45% for a solid and 76% for a skeletonized wall segment, premised on calculations for two layers of CFRP made of 24K rovings with a fineness of 1600 tex at a fiber-volume-fraction of only 50%. This concludes that maximum potential can only arise with optimized fiber path generation. Costs can be saved in terms of material (no fiber blend), molding (3D printed frame), design of fiber path (sys- tematic guidelines), assembly (integral design) and manufacture (robotic production). The advantages will be demonstrated with a generic non-in-situ-sensory 1U CubeSat because it is easy to compare it to other systems due to the strict design specifications. The paper will include detailed information on the design of the robotic fiber deposition head, the modular and adjustable frame, the winding pattern generation and the mechanical testing.

Abstract

In modern architecture branched supporting structures are increasingly used. Until now, these branched columns can only be produced in an extensive and cost-intensive way. A new concept made of fibre-reinforced plastic (FRP) serving as a formwork and a load-bearing hull for a concrete core makes it possible to produce a wide variety of different forms and geometries. To enable the potential of complex branched geometries, especially continuous load-confirming fibre arrangements over the entire braiding hull and large diameters, an advanced braiding technique to create triaxially braided preforms is required. This paper focuses on recent developments of an advanced braiding process to fabricate a multi-layered complex structural geometry on a 144 bobbins radial braiding machine and the adaptation of stationary threads until now regulated by spring force into ones operated electronically. With the new braiding technique, branched performs with triaxial braids were produced. Subsequent to impregnation with a thermosetting resin and annealing, the FRP-hull is poured with concrete. To evaluate a potential load increase of load capacity of the concrete core due to the confinement of FRP-hulls compression tests are conducted. In comparison to plain concrete specimens the mechanical parameters of fibrereinforced plastic-concrete-composites show a significant increase in compression strength.

Abstract

Hingeless shading systems inspired by nature are increasingly the focus of architectural research. In contrast to traditional systems, these compliant mechanisms can reduce the amount of maintenanceintensive parts and can easily be adapted to irregular, doubly curved, facade geometries. Previousmechanisms rely merely on the reversible material deformation of composite structures with almost homogeneous material properties. This leads to large actuation forces and an inherent conflict between the requirements of movement and the capacity to carry external loads. To enhance the performance of such systems, current research is directed at natural mechanisms with concentrated compliance and distinct hinge zones with high load-bearing capacity. Here, we provide insights into our biological findings and the development of a deployable structure inspired by the Flexagon model of hindwings of insects in general and the hierarchical structure of the wing cuticle of the shield bug (Graphosoma lineatum). By using technical fibre-reinforced plastics in combination with an elastomer foil, natural principles have been partially transferred into a multi-layered structure with locally adapted stiffness. Initial small prototypes have been produced in a vacuum-assisted hot press and sustain this functionality. Initial theoretical studies on test surfaces outline the advantages of these bio-inspired structures as deployable external shading systems for doubly curved facades.

Abstract

This paper presents results of the investigation of two biological role models, the shield bug (Graphosoma italicum) and the carnivorous Waterwheel plant (Aldrovanda vesiculosa). The aim was to identify biological construction and movement principles as inspiration for technical, deployable systems. The subsequent processes of abstraction and simulation of the movement and the design principles are summarized, followed by results on the mechanical investigations on various combinations of fibers and matrices with regard to taking advantage of the anisotropy of fiber-reinforced plastics (FRPs). With the results gained, it was possible to implement defined flexible bending zones in stiff composite components using one composite material, and thereby to mimic the biological role models. First small-scale demonstrators for adaptive façade shading systems – Flectofold and Flexagon – are proving the functionality.

Abstract

Brücken und Dächer werden oft durch verzweigte Stahlstützen getragen. Diese sind in ihrer Herstellung meist teuer und energieaufwendig. In der Natur gelingt es Pflanzen, ähnlich stabile und häufig noch komplexere Verzweigungen durch natürliche Wachstumsprozesse zu bilden. Sie können mechanischen Belastungen mühelos standhalten, wie zum Beispiel ihrem Eigengewicht, Winddruck, Schneelast oder schweren Früchten. Um den Erfolgsstrategien verzweigter Bäume und Sträucher auf den Grund zu gehen und von ihnen für die Architektur zu lernen, bedarf es nicht nur eines genauen Blicks auf die Form der Verzweigung und ins Innere der Pflanzen. Auch Computermodelle sowie neue Materialien und Methoden für die Herstellung verzweigter Stützstrukturen im Bauwesen sind für solche Übertragungen in die Technik notwendig.

Abstract

In order to sustainably establish carbon fiber reinforced polymer composites (CFRPC) in the market on an industry scale, solutions on how to recycle these new materials have to be developed. Quasi-continuously aligned carbon staple fiber structures in organic sheets made of recycled carbon are one approach which will be dealt with in this article. The process chain as well as the mechanical properties will be presented. Moreover, the specific feature of staple fiber yarns to be able to plastically deform under process temperature, enabling new degrees of deep-drawing of CFRPC organic sheets in the thermoforming process, will be highlighted.

Abstract

Smart and adaptive outer façade shading systems are of high interest in modern architecture. For long lasting and reliable systems, the abandonment of hinges which often fail due to mechanical wear during repetitive use is of particular importance. Drawing inspiration from the hinge-less motion of the underwater snap-trap of the carnivorous waterwheel plant (Aldrovanda vesiculosa), the compliant façade shading device Flectofold was developed. Based on computational simulations of the biological role-model's elastic and reversible motion, the actuation principle of the plant can be identified. The enclosed geometric motion principle is abstracted into a simplified curved-line folding geometry with distinct flexible hinge-zones. The kinematic behaviour is translated into a quantitative kinetic model, using finite element simulation which allows the detailed analyses of the influence of geometric parameters such as curved-fold line radius and various pneumatically driven actuation principles on the motion behaviour, stress concentrations within the hinge-zones, and actuation forces. The information regarding geometric relations and material gradients gained from those computational models are then used to develop novel material combinations for glass fibre reinforced plastics which enabled the fabrication of physical prototypes of the compliant façade shading device Flectofold.

Abstract

Although there are several methods for describing the absorption behaviour of textile structures, there is no such one yet for identifying the material and fluid parameters that are necessary for simulating the dynamics of the capillary rise of fluids in textile structures. This contribution describes a parameter identification method for a general model for wicking in capillary systems composed of a porous material and a liquid. The resulting characterisation enables modelling and optimising wicking of fluids in textile structures – not only from a static point of view, but as well from a dynamic one. With such acquired knowledge, it is possible to optimise e.g. the wicking effect or liquid absorption volume in absorber structures by modifying the product’s composition, its construction, and surface finish. The contribution describes the underlying model from a physical-mathematical point of view and shows sample characterisations for vertical and horizontal wicking of sunflower oil in hydro-entangled cotton nonwovens.

Abstract

Pflanzen besitzen weder Muskeln noch „klassische“ lokale Gelenke – und können sich dennoch bewegen. Im Laufe der Evolution sind effiziente Bewegungsmechanismen und ästhetische Bewegungsformen entstanden. Aus diesem „Angebot“ der Botanik schöpfen Architekten und Ingenieure in Zusammenarbeit mit Biomechanikern Inspiration für die Entwicklung neuartiger Verschattungssysteme für moderne Gebäude.

Abstract

Die Natur schafft komplexe, effiziente Strukturen bei minimalem Materialverbrauch. Die dabei verwendeten Bauprinzipien mit intelligentem Einsatz von Materialien und deren spezifischen Eigenschaften lassen sich in die moderne Fertigungstechnik übertragen. Ziel ist, deutlich leichtere, funktionale Bauteile ressourcensparend herzustellen. In diesem Kapitel zeigen wir, wie dieser bionische Transfer durch die Weiterentwicklung von Fertigungsverfahren wie der Fasertechnik (Pultrusion), dem 3D-Druck, der Betonteileherstellung und einer Kombination dieser drei Techniken abläuft.

Abstract

In technical constructions, movements are usually achieved by articulated rigid elements. In such cases, the most common cause for failure is mechanical abrasion. Plants are able to perform reversible movements without employing “true” hinges and possess an anisotropic material structure. Moreover, plants generally mechanically adapted to local stress- and strain-concentrations. By this, plants are of high interest for the field of biomimetic architecture since deployable structures, e-g- common shading systems, usually incorporate “classical” technical hinges. The internal structure of plants resembles fiber reinforced plastics (FRPs) consisting of a shaping matrix enveloping reinforcing fibers. By using FRPs in construction engineering, it is possible to generate anisotropic properties within defined regions so that stiff and elastically deformable areas in one component are achievable. The movement principle of traps of the aquatic, carnivorous plant Aldrovanda vesiculosa (waterwheel plant) serves as inspiration for a bio-inspired shading system, Flectofold.

Abstract

In architecture and construction engineering, a vast number of connections and branched columns in frame structures exist that are exposed to high static and dynamic loads. The manufacture of many of these elaborate structures is both time-consuming and costly. Industry has no solution for cost-effectively producing aesthetic and mechanically stable branched columns. This challenge is addressed by the development of branched structures inspired by branched biological concept generators such as Schefflera arboricola. Here, we present methodological approaches allowing the reconstruction of the outer shape and inner structure of complex branching regions, such as in S. arboricola, by using and combining three-dimensional-image stacking of histological thin sections, micro-computer-tomography (μCT) imaging and laser scanning. Computer-aided design (CAD) and Finite Element (FE) models of such structures can then be produced that not only help to provide a better understanding of the functional morphology and biomechanics of the biological concept generator, but also render the basis for the intended biomimetic transfer to branched columns consisting of a braided hull filled with concrete. The current project results are mainly based on the analysis of S. arboricola branching and the results of a previous research project (SPP 1420) in which biomimetic branched fibre-reinforced plastic (FRP) columns inspired by the branching structure of Dracaena were produced. Currently a biomimetic hull geometry that can be manufactured industrially is developed. Initially, branched FRPs based on triaxial braids with readily adjustable mechanical properties are filled with concrete and thus shall achieve sufficient mechanical properties for application and cost-effective fabrication in the building industry.

Abstract

A pultrusion process for producing spatial continuous fiber reinforced plastic profiles with uv-curing resins has been developed. Instead of using a rigid steel die, a uv-transparent flexible die has been used which allows a broad variety of bending radii. This development was driven by the need for concrete armory following the flux of force for the use in porous gradient concrete. The usage of fibers other than transparent glass fibers like carbon- and basalt fibers in combination with uv-resins was made possible through the utilization of peroxides. For material characterization purpose straight profiles made of glass and basaltfibers were produced. Subsequently a process to produce spatial profiles was developed.

Abstract

The transformation of biological paradigms into building construction involves the transfer of structure and system-defining properties from biological role models to construction-specific and innovative non-construction-specific systems and processes. The challenge of manufacturing biomimetic and bio-inspired structures includes the provision of methods and procedures that allow the mapping of biological features on a production-related description. The methodological approach requires the validation and verification of existing production methods at the small scale (model, elementary cell) in order to transfer findings to the production of components at the construction scale. Additionally, the biological features that cannot be reproduced by existing methods require further adjustment or the development of new methods for appropriate transfer. A basic condition for the further development of such production procedures is the possibility of manufacturing complex structures based on biological strategies concerning resource and energy consumption, waste production and greenhouse gas emissions.

Abstract

This paper introduces a novel type of pneumatic actuator, namely the pneumatic textile actuator (PTA). Although the operating principle is similar to pneumatic artificial muscles, design, fabrication and properties of PTAs show significant differences. PTAs consist of double-layered textiles, fabricated in one piece using the Jacquard weaving technology. By filling the chamber between the two layers with pressurised air, one obtains a low-weight, high-power pneumatic actuator at very low cost. The paper first describes the design, fabrication and properties of PTAs in general. Then, the characteristics of a specific PTA are determined experimentally. Moreover, we derive a mathematical model of the dynamic behaviour of the PTA. The model forms the basis for a motion control algorithm, combining flatness-based feedforward and linear feedback control. Finally, the performance of the controller is evaluated experimentally. The results indicate that PTAs are well suited for motion control tasks requiring small displacements but high forces and minimum actuator weight.

Abstract

Plant movements can inspire deployable systems for architectural purposes which can be regarded as ideal solutions combining resilient bio-inspired functionality with elegant natural motion. Here, we first give a concise overview of various compliant mechanisms existing in technics and in plants. Then we describe two case studies from our current joint research project among biologists, architects, construction engineers and materials scientists where the aesthetic movements of such role models from the plant kingdom are analysed, abstracted and implemented in bioinspired technical structures for sustainable architecture. Both examples are based on fast snapping movements of traps of carnivorous plants. The Waterwheel plant (Aldrovanda vesiculosa) captures prey underwater and the Venus flytrap (Dionaea muscipula) snaps in the air. We present results on the motion principles gained by quantitative biomechanical and functional-morphological analyses as well as their simulation and abstraction by using e.g. Finite Element Methods. The Aldrovanda mechanism was successfully translated into a similarly aesthetic and functional technical structure, named Flectofold, which exists in a prototype state. The Flectofold can be used as a façade shading element for complex curved surfaces as existing in modern architecture.

Abstract

Structural health monitoring is an important research topic in the field of fiber reinforced plastics (FRP). An effective way to detect defects or overloads in these FRP has still not been found. One way to monitor the actual state of FRP components is via integrated sensors. Integrating current standard sensors negatively affects the flux of force. Therefore investigations about integration methods of sensors in FRP components have been made. The integration of an optical fiber sensor into FRP profiles via a pultrusion process was investigated. It could be shown that the pultrusion process is suitable method for the integration of fiber optic sensors for strain measurements. Another investigated sensor principle was the integration of piezoelectric polyvinylidene fluoride (PVDF) fibers via a vacuum assisted process. The PVDF fibers were integrated into 3-point bending specimen and the piezoelectric effect was tested with and without polarization. The investigation showed that it is possible to measure the piezoelectric effect of PVDF fibers integrated into a 3-point bending test specimen. It could also be shown that carbon fibers can be used as textile electrodes for the measurement of the generated charge on the PVDF surface.

Abstract

In many areas of fiber composite technology there is a great need for a solution of how to manufacture nodal elements and/or ramifications with an optimized force flow process and by machine, i.e. economically. Examples are hubs of wind power plants, branch points in framework constructions in the building industry and air and space travel, the automotive industry, ramified vein prostheses in medical technology, or the connecting nodes of bicycle frames. Motivated by this, the potential of plant ramifications as a model for new compound fiber constructions was investigated. Ramified species with pronounced fiber matrix structure served, inter alia, as biological models. The PBG Freiburg examined tree-formed monocotyledons of the genera Dracaena and Freycinetia 1, the BTU Dresden column cacti of the genera Pilsocereus and Myrtillocactus 2. The plants exhibit Y-shaped and T-shaped ramifications, whose angles resemble those of the ramified technical construction units that are to be optimised bionically. As the investigations confirm, the ramifications, which are nearly completely unexplored, are characterised by very interesting mechanical characteristics, like e.g. good-natured breaking behavior and good oscillation damping caused by high energy absorption, as well as a high lightweight construction potential. The results demonstrate the high potential for a successful technical transfer of the results of the proposed project.In this paper, three different types of braided branches are represented. Firstly, the aforementioned nature-inspired Y-junctions are shown. Secondly, a type of branch with a special braiding technique that allows branches with asymmetric design of the arms and a braiding technique for the automated production of loop connections is presented.

Abstract

Carbon fiber reinforced plastic (CFRP) was integrated with steel fibers in order to improve the toughness and to enhance the structural integrity during crash. An epoxy system with internal mold release was chosen as the matrix system. The surface modification of steel fibers was done by sandblasting and twisting in order to improve the fiber-matrix adhesion through mechanical interlocking mechanism. The pull-out test of surface modified steel fiber doubled the adhesive strength. The steel fiber integration increased the maximum bending stress of the composites up to 20% whereas the elongation at break reduced to 2.3%. The energy dissipation factor of the steel fiber integrated CFRPs was also reduced compared to CFRPs without steel fiber. An increase in fracture toughness was observed for the CFRPs with steel fibers that amounts to 17 J.

Abstract

The following work was focused on the analysis of adaptable pressurized sandwich components. The investigations were carried out to study the influence of internal pressure on mechanical characteristics. The bonding quality between core material and outer layers is of particular importance. For analyzing the bonding quality peel tests were conducted. In order to investigate the influence of the internal pressure and also of a bonding technique on bending properties four-point bending tests were carried out. In addition, the pressure characteristics were studied with compression tests during which a compression die was pressed into the component. After the compression tests, the rebound properties of pressurized and standard components were observed and compared.

Abstract

Fiber reinforced plastics, due to their good mechanical properties and simultaneously low density, are very attractive for many uses. They are also gaining more importance in the civil engineering applications. Bio composites based on sustainable raw materials are becoming much more attractive, especially in construction industry, due to their recyclability and eco balance benefits. In this paper, a method to develop a façade profile from regenerated viscose filament and bio resin system (PTP®) using pultrusion process is discussed. The PTP® resin system from Bio-Composites And More GmbH comprises of 60% epoxidized vegetable oil. The pultrusion process is optimized to reach 60 cm/min speed from the initial speed of 4 cm/min by modifying the resin mixture. Though the production speeds are below the industrial standards, economic production scale could be still reached.