Niels Modler

Fibre-reinforced composite structures based on thermoplastic matrices with embedded piezoceramic modules

The paper presents recent developments for the integration of piezoceramic modules into fibre-reinforced composite structures based on thermoplastic matrices. An adapted hot pressing technology is conceptualized that allows for material homogeneous integration of the active modules. The main focus of this contribution is on the development of a robust and continuous manufacturing process of such novel active composites as well as on the operational testing of the produced samples. Therefore, selected specimens are manufactured as bending beams and investigated by means of electrical impedance measurements, modal analysis and structural excitation tests. In particular, the functionality of representative specimens is characterized based on frequency as well as spatially resolved deflection measurements. Moreover, the mentioned samples are compared to non-integrated piezoceramic modules and to equivalent passive reinforced composite structures.

Sensitivity analysis for the process integrated online polarization of piezoceramic modules in thermoplastic composites

The use of active composite structures in high-volume applications requires novel robust manufacturing processes as well as specially adapted functional modules. The paper presents actual research results with regard to the process-immanent polarization of novel thermoplastic-compatible piezoceramic modules (TPM) during the consolidation process of active fibre-reinforced thermoplastic composite structures. In particular the influence of varying manufacture process parameters of a hot-press process on the polarization behaviour is investigated. The main principal objective is the purposeful utilization of process parameters for polarization support.

Online Poling of Thermoplastic-Compatible Piezoceramic Modules during the Manufacturing Process of Active Fiber-Reinforced Composites

Due to high specific properties and the ability for the realisation of short cycle times within the production process, the use of fiber-reinforced thermoplastic composites offers a high potential for high volume applications. Furthermore, the layered built-up and the according manufacturing processes of these materials give the possibility to integrate functional elements, like electronic components or piezoelectric sensor/actuator modules. Within the collaborative research center CRC/TRR 39 “Production Technologies for light metal and fiber-reinforced composite-based components with integrated piezoceramic Sensors and Actuators”, the integration of piezoceramic modules into lightweight structures ready for series production is investigated. This paper presents the manufacturing process of active fiber-reinforced thermoplastic composites. Here, the focus is on experimental investigations covering the process-integrated poling of novel piezoceramic modules during the manufacturing of active fiber-reinforced thermoplastic components. Therefore, laboratory and process-oriented tests are performed for the determination of appropriate parameters for the pressing and poling process. The functionality of the embedded and poled TPM is validated by the excitation of an active component structure and the optical measurement of the vibration behaviour using a laser scanning vibrometer.

Numerical evaluation of two‑dimensional micromechanical structures of anisotropic cellular materials: case study for polyurethane rigid foams

This paper deals with evaluating the elastic response of several micromechanical structures used for simulating cellular materials under compression. For this study polyurethane rigid foams were investigated, having three relative densities: 0.085, 0.124 and 0.256. Their microstructure was analysed using SEM images, determining four types of cells that were consequently designed using specialized CAD software: square cells with circular, quadratic and/or hexagonal orifices and hexagonal cells. An interdependent variation of the cells’ geometrical parameters of the proposed structures was determined to obtain geometrical variations at a required relative density. Finite element analysis simulations were performed on the designed microstructural models using a linear elastic material model for the cell struts, resulting in the variation of the elastic modulus of the structure with the variation in cell geometry parameters. The final objective of this work was to determine anisotropic bi-dimensional micromechanical models for the studied cellular material that provides accurate results in compression on both loading directions. The anisotropic models for the proposed cell structures were obtained by generating irregular geometries which provided extra variables for the cell geometry parameters. It was determined that some cell geometries are suitable for simulating lower relative density materials while other cell geometries provide good accordance with experimental data for higher relative density materials.

Intrinsic Lightweight Steel-Composite Hybrids for Structural Components

Multi-Material Design has been identified to be an important enabler for lightweight structures, especially with regards to the goals for the large-scale implementation of e-mobility concepts. A novel 3D-Hybrid technology has been developed to combine the advantages of metal and fibre-reinforced thermoplastics in one structural part. This leads to significant weight reduction in combination with an increase in functionality. Additionally, the amount of single parts can be reduced; these factors combined make the technology competitive with conventional steel-sheet design. Investigations on basic profiles showed the feasibility of the technology in single stage production processes and proved the superior performance of the structure compared to conventional design. Finally, a B-pillar demonstration structure was produced in a highly automated process and investigated in side-impact related component tests.

One vs. two piece customized implants to reconstruct mandibular continuity defects: A preliminary study in pig cadavers

OBJECTIVES The reconstruction of mandibular continuity defects by bridging plates often leads to complications. Customized mandibular implants might be an alternative option. In the present study, the stability at the bone-implant-interface of customized two-piece implants was compared to one-piece implants. METHODS Thirty pig mandibles were randomly divided into three groups. One group (A) was left untreated and served as reference. In groups B and C, a continuity defect was created in the left mandibular side. The defects were reconstructed by customized pure titanium implants, manufactured using the LaserCUSING(®) technology. Group B received a one-piece implant; in group C a two-piece implant was inserted to reconstruct the continuity defect. The bonding strength was examined statically and dynamically under standardized conditions. Digital Image Correlation was used for distortion measurement. Different dynamic measurements were performed for orientation purposes. RESULTS The highest bonding strength was measured for the reference group. The two-piece implant showed an increased bonding strength when compared to the one-piece design. In all pig mandibles treated with individual implants a fracture occurred on the non-operated side. This indicates a high primary stability of the bone-implant-interface. CONCLUSION The two-piece individual mandibular implant manufactured by LaserCUSING(®) technology should be further analyzed in future studies.

Compliant Structures in Book Handling Applications

This paper describes an overview regarding the compliant structures used in library automation context, more precisely in books handling applications. As libraries provide a huge content of printed materials, the automation of books handling becomes a must. In the same point of view, a large amount of routine and repetitive activities will be reduced in the workplace of shelves and in service point. Also, this article presents an innovative design approach in designing library book handling gripper mechanisms. This article proposes one CAD gripper model designed in Solid Works software. The parallel gripper prototype is still in manufacturing process using light-weight glass-fiber reinforced for the material. The CAD model for the gripper and FEM simulation is presented.

Cyclic Test of Textile-Reinforced Composites in Compliant Hinge Mechanisms

The use of so-called compliant elements with specifically adjustable compliances offers the possibility to transmit motions just by structural deformations. This paper makes a contribution to the efficient cyclic test of textile-reinforced compliant structures by developing a novel kinematictest stand realizing pure bending.

[Computation and experimental examination of an implant structure made by a fibre-reinforced building method for the bypass of continuity defects of the mandible].

Zusammenfassung Eine Unterkieferteilresektion muss nicht selten im Rahmen der chirurgischen Entfernung von Tumoren im Unterkiefer-, Mundboden- und Zungenbereich bzw. mit Substanzverlust einhergehenden Unterkieferfrakturen, gutartigen Knochenläsionen und ausgedehnten, schwer zu beherrschenden Knochengewebsentzündungen durchgeführt werden. Die primäre Rekonstruktion des Unterkiefers ist nach einer Teilresektion mit Kontinuitätsverlust vorwiegend aus funktionellen und auch aus ästhetischen Gründen notwendig. Derzeit werden die Unterkieferkontinuitätsdefekte häufig mit metallischen Rekonstruktionsplatten überbrückt, um die mastikatorische Funktion des Unterkiefers temporär oder endgültig wieder herzustellen. Funktionelle sowie ästhetische Nachteile ergeben sich bei der Anwendung derartiger Platten durch einen hohen Steifigkeitssprung zwischen Rekonstruktionsplatte und Knochen sowie deren wenig individuell gestaltetes Design. Der Einsatz von biokompatiblem, kohlenstofffaserverstärktem Polyetheretherketon (CF-PEEK) erlaubt die Entwicklung einer dem Unterkiefer kontur- und steifigkeitsangepassten Tragstruktur. Für die beanspruchungsgerechte Auslegung und den Test einer CF-PEEK-Tragbandage bieten sich die Finite-Elemente-Methode sowie die Anwendung optischer Methoden wie etwa das Grauwertkorrelationsverfahren an. Das Deformationsverhalten wurde für verschiedenartige Osteosynthesekonfigurationen an einem Modellkiefer vergleichend untersucht. Die Berechnungen und Tests des defektüberbrückten Modellkiefers zeigen beim Einsatz der neuartigen CF-PEEK-Tragbandage im Vergleich zur Verwendung herkömmlicher Titan-Osteosyntheseplatten ein dem natürlichen Unterkiefer wesentlich besser angepasstes mechanisches Verhalten. Abstract A partial resection of the lower jaw often has to be carried out in the context of the surgical removal of tumours in the lower jaw, mouth and tongue-floor space and lower jaw fractures with loss of substance, benign bone lesions and extensive difficult inflammation of bone tissue, respectively. The primary reconstruction of the lower jaw after partial resection with loss of continuity is mainly important for functional and aesthetic reasons. The defects of lower jaw continuity are often bridged with metal plates to reconstruct the masticatory function of the lower jaw, temporarily or permanently. Functional as well as aesthetic disadvantages arise in the case of the application of such plates as a result of a high stiffness jump between reconstruction plate and bone and their insufficiently individual design. The employment of biocompatible, carbon-fibre-reinforced Polyetheretherketon (CF-PEEK) permits the development of a geometry- and stiffness-adapted carrying structure for the mandible. For the demand-adapted dimensioning and the test of a CF-PEEK bandage, the application of optical methods, such as the grey value correlation method, is suited as well as numeric methods, such as the finite element method. In an initial analysis of deformation behaviour, the various osteosynthesis configurations are comparatively investigated on a model jaw. The calculations and tests of the lower jaw model show that the use of the new CF-PEEK bandage compared to the use of conventional titanium osteosynthesis plates shows a mechanical behaviour which is much better adapted to the natural lower jaw.A partial resection of the lower jaw often has to be carried out in the context of the surgical removal of tumours in the lower jaw, mouth and tongue-floor space and lower jaw fractures with loss of substance, benign bone lesions and extensive difficult inflammation of bone tissue, respectively. The primary reconstruction of the lower jaw after partial resection with loss of continuity is mainly important for functional and aesthetic reasons. The defects of lower jaw continuity are often bridged with metal plates to reconstruct the masticatory function of the lower jaw, temporarily or permanently. Functional as well as aesthetic disadvantages arise in the case of the application of such plates as a result of a high stiffness jump between reconstruction plate and bone and their insufficiently individual design. The employment of biocompatible, carbon-fibre-reinforced Polyetheretherketon (CF-PEEK) permits the development of a geometry- and stiffness-adapted carrying structure for the mandible. For the demand-adapted dimensioning and the test of a CF-PEEK bandage, the application of optical methods, such as the grey value correlation method, is suited as well as numeric methods, such as the finite element method. In an initial analysis of deformation behaviour, the various osteosynthesis configurations are comparatively investigated on a model jaw. The calculations and tests of the lower jaw model show that the use of the new CF-PEEK bandage compared to the use of conventional titanium osteosynthesis plates shows a mechanical behaviour which is much better adapted to the natural lower jaw.

An Approach for a Mathematical Description of Human Root Canals by Means of Elementary Parameters

Introduction Root canal geometry is an important factor for instrumentation and preparation of the canals. Curvature, length, shape, and ramifications need to be evaluated in advance to enhance the success of the treatment. Therefore, the present study aimed to design and realize a method for analyzing the geometric characteristics of human root canals. Methods Two extracted human lower molars were radiographed in the occlusal direction using micro–computed tomographic imaging. The 3‐dimensional geometry of the root canals, calculated by a self‐implemented image evaluation algorithm, was described by 3 different mathematical models: the elliptical model, the 1‐circle model, and the 3‐circle model. Results The different applied mathematical models obtained similar geometric properties depending on the parametric model used. Considering more complex root canals, the differences of the results increase because of the different adaptability and the better approximation of the geometry. Conclusions With the presented approach, it is possible to estimate and compare the geometry of natural root canals. Therefore, the deviation of the canal can be assessed, which is important for the choice of taper of root canal instruments. Root canals with a nearly elliptical cross section are reasonably approximated by the elliptical model, whereas the 3‐circle model obtains a good agreement for curved shapes.