Peter Middendorf

Peter Middendorf
Universität Stuttgart · Institute of Aircraft Design

Professor

About

216
Publications
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1,428
Citations

Publications

Publications (216)
Chapter
Additive manufacturing processes in combination with topology optimization offer great potentials for lightweight design. In this work, the engine mount of a Unmanned Aerial Vehicle (UAV) is topology optimized to minimize weight for a given stiffness. The solutions are carried out taking into account the different material properties of Acrylnitril...
Conference Paper
This paper deals with spread carbon fibre tows fixed by epoxy-based reactive binder that can be used in two-dimensional dry fibre placement (DFP) layups, which show freely selectable fibre orientation of each tow and layer structure. In a second step, the DFP preforms can be draped into a three-dimensional preform, here the bending stiffness has a...
Article
Full-text available
While fiber reinforced polymers in fused filament fabrication (FFF) provide improved tensile properties in bead direction, only low properties can be reached perpendicular to the bead direction. The effects of process parameters on interlayer and bead-to-bead bonding of a short carbon fiber (0.1–0.3 mm) reinforced polyamide were investigated using...
Article
Residual burst pressure of thick composite pressure vessels related to low-velocity impacts is investigated numerically. Different modelling approaches from simple shell to complex 3D solid models with multiple delamination interfaces are compared. Burst pressure without impact is used to estimate the quality of the different approaches, whereby th...
Article
Dry fibers or fabrics do not possess an inherent tack, when compared to prepreg materials. In order to fixate dry fiber fabrics onto tooling geometries, auxiliary binder systems are necessary. These tackifying agents vary in terms of chemical composition and reactivity, processing parameters and appearance. One key aspect for most automated fiber p...
Article
In the coreless filament winding process (CFW) anchor points are wrapped with pre-impregnated fibre bundles (Towpregs) in a defined chronological order. With this process, fibre-polymer composite structures with a very high lightweight potential and very little material consumption can be created for different applications in the automotive, aerona...
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Full-text available
Additive manufacturing of polymers offers great potential for the production of complex structures. In particular, Fused Filament Fabrication (FFF) processes can be used to create functionally integrated components, in addition to easy handling, tool-free production and large material options. By combining a FFF system with a robot, inserts of diff...
Article
This study investigates the influence of reduced graphene oxide (rGO) coated glass fabrics on the strain sensing and the mechanical characteristics of fiber‐reinforced composites. Graphene oxide was applied in two thicknesses (threefold and fivefold coatings) onto a fabric using a padder mangle machine followed by thermal reduction and infused with...
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Full-text available
A suitable functionalization of graphene and its derivatives can further enhance the material properties of nanocomposites. In contrast to chemical functionalization methods that have been extensively researched, functionalization by plasma treatment is relatively unexplored. In this work, we compare the mechanical, thermal and electrical character...
Article
In structural optimization of fiber-reinforced composites, unidirectional design material is normally applied due to its high anisotropy character. Using volume constraints to save weight often results in truss-like frameworks with defined tension and shear loaded areas, while the latter one is often neglected or improperly described with unidirect...
Article
The computational analysis of adhesives within finite element simulations is important for many engineering applications, from automotive structures to civil engineering. The underlying material descriptions are closed, analytically formulated models representing the stress-response of the material for given strains. In this publication, we investi...
Article
This paper looks at a novel foldcore-foam hybrid sandwich structure developed to provide extreme heat resistance. The sandwich consisting of mostly inorganic components is characterized for compressive strength, temperature resistance and thermal conductivity. Foam and foldcore components are both analyzed individually and in combination for compre...
Article
This paper presents novel insights of a numerical bolt representation approach taking into account damage and failure, suitable for large-scale models as in full vehicle crash simulations. Custom-built experimental equipment combined with digital image correlation enables observation of bolt failure behavior and its physical characteristics under t...
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Full-text available
In coreless filament winding, resin-impregnated fibre filaments are wound around anchor points without an additional mould. The final geometry of the produced part results from the interaction of fibres in space and is initially undetermined. Therefore, the success of large-scale coreless wound fibre composite structures for architectural applicati...
Chapter
One of the main advantages of additive manufacturing by Fused Filament Fabrication is its wide variety of materials and cost-effective production systems. However, the resolution and tightness of the produced structures are limited. The following article describes a novel approach of the functional integration of stereolithographic produced subcomp...
Article
Robotic fabrication plays an essential role for the construction industry in the pursuit of higher productivity and greater flexibility. Modular robotic systems enable the off-site prefabrication of components for high-performance building systems from wood or fiber composites, while digital planning methods and computational design enable the effi...
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Full-text available
Within the dry fibre placement (DFP) process, spread and pre-bindered carbon fibre rovings are automatically processed into dry textile preforms using 2-D and 3-D laying systems. The aim was to automate existing hand lay-up processes, reducing the complexity, increasing ro-bustness, and facilitating the handling of the DFP technology. Process relia...
Conference Paper
Fused Filament Fabrication (FFF) is becoming increasingly important in the automotive industry as it enables the additive manufacturing (AM) of short fiber reinforced plastic components. AM of composites enables load bearing and highly stiff parts for the use in automotive applications (jigs, fixtures, functional prototypes). During the process, mo...
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Full-text available
In this study, optically transparent glass fiber-reinforced polymers (tGFRPs) were produced using a thermoset matrix and an E-glass fabric. In situ polymerization was combined with liquid composite molding (LCM) techniques both in a resin transfer molding (RTM) mold and a lite-RTM (L-RTM) setup between two glass plates. The RTM specimens were used...
Conference Paper
The substitution of classical constitutive material models with data-driven models supported by machine learning techniques could provide a leap in the modelling of materials. The most notable benefits are a faster description of new materials without a tedious manual parameter identification procedure, lower computational time for simulations due...
Conference Paper
In the field of additive manufacturing, photopolymers are often insufficient for structural application due to their limited mechanical properties. In this study, the reinforcement of stereolithography structures by subsequent infusion of a short carbon fiber filled epoxy resin is studied. For this purpose, infusion under vacuum and pressure castin...
Conference Paper
This paper deals with spread carbon fibre tows with epoxy-based thermoplastic binder that can be used in two-dimensional dry fibre placement (DFP) layups, which show freely selectable fibre orientation of each tow and layer structure. In a second step the DFP preforms can be draped into a three-dimensional preform, here the friction has a significa...
Article
Full-text available
This study evaluates the effect of plasma surface functionalization of reduced graphene oxide particles on the processing characteristics and homogeneity of dispersion of a bisphenol A‐(epichlorhydrin) epoxy matrix and amine‐based hardener with varying weight fractions from 0.00 to 1.50 wt%. It was observed that amine‐functionalized reduced graphen...
Conference Paper
Full-text available
This paper presents a novel virtual process chain capable of evaluating the mechanical properties of foldcores under shear loading. The aim of the method presented in this paper is to find the optimal foldcore geometry with given boundary conditions. This includes the optimization of stiffness and strength, and the evaluation of the anisotropy and...
Conference Paper
Folded sandwich core structures are an emerging technology for lightweight applications. A decisive factor in the mechanical properties of Miura-ori foldcores is the occurrence of deviations from the mathematically designed geometry due to the manufacturing process, called imperfections. To consider these deviations in the structural simulation of...
Article
Purpose During post-processing of stereolithography photopolymers, the limited penetration depth of ultraviolet (UV) light can lead to inhomogeneous cross-linking. This is a major problem in part design for industrial applications as this creates uncertainty regarding the mechanical load capacity. Therefore, this paper aims to present an experiment...
Article
In this paper a systematic experimental and numerical study on mechanical design features to arrest fatigue crack growth in adhesive joints is performed. A material model for fatigue crack growth analysis based on a cohesive zone element formulation is presented together with a methodology to compare design features and to identify and quantify fun...
Article
Our research aims to develop a shear forming envelope for the preforming of textiles, a critical step in the manufacture of fibre-reinforced composite materials. This paper demonstrates the progress towards this aim by conducting picture frame tests to empirically determine the locking angle of non-crimp fabrics with different fibre orientations. W...
Conference Paper
For the production of automotive interior parts, there is a high demand regarding the surface quality combined with large production rates. These requirements can potentially be achieved by using Stereolithography (SL). This work concerns the dimensional limitations of depth of cure during UV-post-curing of parts made of urethane acrylates by Digi...
Article
In this study, the electromechanical properties and strain monitoring behavior of graphene-coated glass fiber reinforced epoxy (GGFRE) composites were investigated. Glass fabrics were first coated with 2 wt% graphene dispersions using a blade coating method and composites of these graphene-coated glass fabrics were manufactured using vacuum resin i...
Article
The out-of-plane permeability of two glass fibre fabrics was measured by 26 institutions using silicone oil as a test fluid. Participants in this study were free to select the test procedure, specimen dimensions and data analysis method, provided that testing was carried out at three target fibre volume fractions, 46 %, 50 % and 54 %. While results...
Article
In this work, the influence of milled and chopped carbon and glass fibers on the curing behavior and accuracy of the acrylic-based photopolymer LOCTITE 3D 3860 was investigated. The analysis was performed using working curves and optical methods. A comparison between the two fiber types showed that using glass fibers leads to increased volume effic...
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Full-text available
Simulations at microscopic scale are subject of research in many fields of continuous fiber reinforced materials. They allow the virtual characterization with clearly defined boundary conditions and the investigation of effects that cannot easily be observed in experimental tests, such as crack initiation. While the influence of differently detaile...
Conference Paper
One of the main advantages of additive manufacturing by Fused Filament Fabrication is its wide variety of materials and cost-effective production systems. However, the resolution and tightness of the produced structures are limited. The following article describes a novel approach of the functional integration of stereolithographic produced subcomp...
Conference Paper
In order to implement individual component variants within a large injection molding series, the in situ joining of additively manufactured subcomponents is investigated in the present study. To determine the maximum tensile strength of the joining area geometry, halved tensile specimen are first produced from thermoplastic polyamide 6 (PA6) using...
Conference Paper
The production efficiency of stereolithographic manufacturing processes (SLA) is limited by the typical layer-based manufacturing process and a static exposure strategy. The smallest geometry to be realized on the part determines the global printing accuracy and usually leads to long manufacturing times. Using two-photon polymerization (2PP), the p...
Article
In Liquid Composite Molding (LCM) processes, a fabric reinforcement is placed in a closed cavity and resin is injected into the mold. Almost all reinforcements are dual scale containing fiber tows, which fill at a different rate than the region in between the fiber tows. Simulation of LCM processes can help identify regions that fail to fill. Howev...
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Full-text available
At present, the simulation cannot satisfactorily reproduce the actual vibration behavior of short-fiber reinforced plastics. This is because the required linear-viscoelastic material properties, in particular damping, are often not usable in the desired frequency range of up to 10 kHz. For this purpose, a newly reconsidered test method as an altern...
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Full-text available
This paper investigates the manufacture of biaxial carbon fiber braids and the influence that different machine settings have on variability of the textile architecture produced. In parallel, numerical simulations of the braiding process with these different machine settings have been conducted. For these studies yarn tension and process speed are...
Article
Composite materials have brought new development and sizing possibilities for structural components in transportation systems. Their high specific material properties are enabling weight reduction while increasing structural performance. On the downside, composite materials are generally related to high material and manufacturing costs and increase...
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Full-text available
Under normal conditions, the cross-sections of reinforced concrete in classic skeleton construction systems are often only partially loaded. This contributes to non-sustainable construction solutions due to an excess of material use. Novel cross-disciplinary workflows linking architects, engineers, material scientists and manufacturers could o�er a...
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This paper reports the results of an international benchmark exercise on the measurement of fibre bed compaction behaviour. The aim was to identify aspects of the test method critical to obtain reliable results and to arrive at a recommended test procedure for fibre bed compaction measurements. A glass fibre 2/2 twill weave and a biaxial (±45°) gla...
Article
Commercial development of gaseous hydrogen storage in fuel cell electric vehicles is inevitably subjected to reliable and cost-effective design of composite pressure vessels. In this context, certainty in the design process is sought, which is determined by how well the vessel's mechanical response is understood, but more importantly to which accur...
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Full-text available
This paper investigates the possibility of producing an equivalent structural behaviour of two components each consisting of a different material. This is achieved through the implementation of structural optimizations. It is assumed that the initial structure is produced by conventional injection moulding and the structure to be optimized is 3D pr...
Article
In this paper a new virtual process chain is presented that allows a fast mechanical characterization of foldcores under flatwise compression. The aim is to find the best possible folded configuration with limited overall geometry dimensions providing highest mechanical properties for strength and stiffness under compressive loading. For this purpo...
Article
In this paper, both location and energy of impacts on an anisotropic carbon fiber reinforced plate (CFRP) are detected with the help of deep learning. We introduce sparse low-cost sensor array integration in CFRP plates that allows for structural monitoring of lightweight structures. Using a resin transfer moulding process microelectromechanical sy...
Article
Fiber Reinforced Polymers (FRPs) are increasingly popular building materials, mainly because of their high strength to weight ratio. Despite these beneficial properties, these composites are often fabricated in standardized mass production. This research aims to eliminate costly molds in order to simplify the fabrication and allow for a higher degr...
Conference Paper
The use of compliant hinges as integral elements of origami-based and origami-inspired structures can provide significant benefits compared to other hinge concepts, namely ease of integration , durability and tunable stiffness, range and target positioning of the hinge. So far, mostly classical straight-crease constructions have been used for the a...
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Full-text available
In Selective Laser Sintering, fibres are strongly orientated during the powder recoating process. This effect leads to an additional increase of anisotropy in the final printed parts. This study investigates the influence of process parameter variation on the mechanical properties and the fibre orientation. A full factorial design of experiment was...
Conference Paper
This study presents basic strategies for transfer of LS-DYNA® material card parameters from 2D- to 3D-discretizaion without extensive recalibration. The responses of a material card, calibrated on two-dimensional shell elements, are shown on single-element tests with different element formulations, on multi-element patches and on coupons. From this...
Conference Paper
Full-text available
At present, the simulation cannot satisfactorily reproduce the actual vibration behavior of short-fiber reinforced plastics. This is because the required viscoelastic material data, in particular damping, is often not available. For this purpose, a new experimental method was developed which can characterize the exact stiffness and damping of the m...
Article
During the autoclave manufacturing of sandwich components, several defects may arise. A typical defect in the use of honeycombs is core crush. The occurrence of this defect depends, among other things, on the angle of the honeycomb chamfer. To design this angle, the friction between honeycomb and prepreg must be known. Due to the low rigidity of No...
Article
Test and simulation of low-velocity impact and residual strength of composite structures is usually limited to relatively thin laminates. However, numerous applications in the aerospace and automotive industry exist, such as high-lift devices and pressure vessels that have thick laminates with notably different damage mechanisms to thin laminate. T...
Chapter
Disbond-arrest features for adhesively bonded composite joints, which present an enabling technology for integral design solutions.
Chapter
Zur Validierung der integrierten Funktionen wurden funktionale Tests an Komponenten des LeiFu-Unterbodens durchgeführt. Hierbei wurden exemplarisch das Crashverhalten, das NVH-Verhalten, die thermische Isolation bzw. Abstrahlung sowie integrierte elektrische als auch sensorische Funktionen experimentell validiert. Des Weiteren erfolgt in Kap. 8 die...
Chapter
Bei der Entwicklung funktionsintegrierter Bauteile aus Faserverbundkunststoffen sind, neben den technischen Herausforderungen, auch die wirtschaftlichen Rahmenbedingungen von großem Interesse. Im Rahmen des Projekts LeiFu wurden die Herstellkosten verschiedener Komponentengruppen berechnet. Inhalt der Bewertung Leichtbaukosten ist eine Analyse der...
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Full-text available
This paper presents the application of printed strain sensors during the characterization of textile forming mechanisms. Using the example of trellis shearing, these sensors are applied to a fabric and shearing is performed in a picture-frame based shearing test rig. As the textile shears, opposite corners of the cruciform specimen start to move ap...
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Full-text available
Fiber-reinforced plastics parts produced in medium or large quantities can be manufactured by forming flat textile fabrics to a component contour. Due to the stiffness of fibrous semi-finished products, forming of complex geometries with an uncut fabric is not always possible. Various effects in the fabric structure can occur, that affect the funct...
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Full-text available
The friction between carbon filaments has a big impact on the deformation of dry yarns. Therefore, to simulate the deformation of yarns on a microscopic level, it is very important to obtain the true friction coefficient at different boundary conditions. The stiffness properties of the yarns change when other parameters, such as the fiber volume co...
Article
de Sandwichkonstruktionen kommen im Leichtbau, vor allem im Flugzeugbau, im Transportwesen, dem Bauwesen oder auch im Möbelbau zum Einsatz. Sie sind aufgrund des geringen Flächengewichts und der Vielfältigkeit flexibel einsetzbar. Sandwichkonstruktionen bestehen typischerweise aus zwei Deckschichten, die im Verbund mit einer leichten Kernschicht St...
Chapter
Für die Digitalisierung der Fertigungstechnologien und die Anknüpfung an die Industrie 4.0 ist eine korrekte Abbildung der Prozesssimulationen mit zugehöriger CAM-Schnittstelle unumgänglich. Hierbei ist es wichtig, das reale Verhalten der Werkstoffe und der Maschinen abzubilden, da der nahtlose Übergang von der Simulation zu den Produktionsmaschine...
Chapter
Das Projekt DigitPro – „Ganzheitlicher digitaler Prototyp im Leichtbau für die Großserienproduktion“ wurde im Rahmen der ARENA2036 als eines der ersten Startprojekte des neuen Forschungscampus ins Leben gerufen. Das Projekt startete im Juli 2013 und endete im Juni 2018.
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Der Forschungscampus ARENA2036 ist ein neuer, langfristiger Projektansatz, der vom deutschen Bundesministerium für Bildung und Forschung (BMBF; Forschungscampus ARENA2036) finanziert wird. Er ist einer der neun großen wissenschaftlichen Campi in Deutschland und ist der einzige, der direkt in die Hauptphase (Phase 1) gestartet ist. Die ARENA2036 bef...
Chapter
Wie bereits in der Einleitung des Buches beschrieben, verbindet die im Digitalen Prototyp integrierte CAM-Schnittstelle die Simulationen mit der realen Fertigung. Die Motivation für die Umsetzung einer CAM-Schnittstelle liegt neben der Reduzierung manueller Fertigungstätigkeiten vor allem auch in der Generierung gleicher Ausgangszustände für Simula...
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Zusammenfassend kann nach fünf Jahren Projektlaufzeit und dem erfolgreichen Abschließen der ersten Förderphase ein positives Resümee gezogen werden. Projektinhalte wurden umgesetzt, erfüllt und eine erste lauffähige Version des Digitalen Prototyp programmiert. Es konnte gezeigt werden, dass durch den Einsatz eines Digitalen Prototyp und neuer Softw...
Book
Der Forschungscampus ARENA2036 ist ein neuer, langfristiger Projektansatz, der vom deutschen Bundesministerium für Bildung und Forschung (BMBF; Forschungscampus ARENA2036) finanziert wird. Er ist einer der neun großen wissenschaftlichen Campi in Deutschland und ist der einzige, der direkt in die Hauptphase (Phase 1) gestartet ist. Die ARENA2036 bef...
Article
Full-text available
Through-thickness stitching, in the form of tufting, has been shown to be a potentially successful method of improving resistance to delamination. Tufting is a single-sided stitching technique that involves the insertion of a yarn through a fabric, in the z-direction. However, further research into the development of a tailored tufting yarn could y...