HYBRID 3D WOVEN STRUCTURES FOR CONCRETE REINFORCEMENT UNDER IMPACT LOADING PART 1: DEVELOPMENT OF A BI-AXIAL CORE DESIGN

Steel reinforced concrete (RC) is extensively used in the construction industry due to its high strength, durability, and versatility. Nonetheless, its resilience under dynamic loads, such as impact, remains particularly low. The research training group DFG GRK 2250 aims to significantly improve the impact energy absorption of existing infrastructures by applying thin layers of an innovative strengthening material composed of a strain hardening cementitious composite and a novel textile reinforcement. This paper investigated methods for manufacturing 3D hybrid woven fabrics with a core incorporating spatial elements in both the weft and warp directions, based on a bi-axial core design. The challenges associated with shaping spatial elements before and during the weaving process were discussed, with the latter proving to be the optimal choice when combined with carbon fiber towpregs. After developing the structural design, selecting the materials for each element, and establishing the fabric binding pattern, a demonstrator was successfully produced using a modified rapier weaving machine

A random finite set approach for dynamic occupancy grid maps

Reliable vehicle environment perception is a basic prerequisite for advanced driver assistant systems and autonomously driving cars. A common environment representation form is an occupancy grid map. It divides the environment into single grid cells and estimates for each cell whether the space it represents is occupied or free, assuming grid cells are independent of each other. The mathematical framework is based on the binary Bayes filter (BBF), which combines sensor measurements from different sensors and potentially from different points in time. Since an occupancy grid map does not employ a concept of individual objects, it is able to represent arbitrarily shaped obstacles. A classical occupancy grid map is not eligible for estimating dynamic environments, because it does not apply a process model. A much-noticed extension to a static occupancy grid map is the Bayesian occupancy filter (BOF). In contrast to a classical occupancy grid, the BOF estimates a velocity distribution for the occupancy of each grid cell based on a histogram filter. Since the BOF is computationally extremely demanding, recent publications suggest to represent the dynamic state of grid cells with particles. This allows to calculate dynamic grid maps in real-time applications with increased grid cell size and resolution. Today, dynamic occupancy grid maps are still a younger research area and not as well-studied as object-tracking approaches are. Up to now, the BOF has been addressed as a research field with little connection to other tracking methods. This work presents a new concept of dynamic grid mapping as an approximation of a random finite set (RFS) filter. A random finite set is a general, probabilistic representation of a random but limited number of objects and their states. The finite set statistics (FISST) describe Bayesian filtering of random finite sets and are basis for a number of multi-object tracking approaches like the probability hypothesis density (PHD) filter. Describing the grid as a random finite set allows transferring advanced concepts from the well-established field of random finite set filtering to the field of dynamic grid mapping. The thesis derives a filter called probability hypothesis density / multi-instance Bernoulli (PHD/MIB) filter, which represents and propagates the dynamic grid map in alternating forms as a PHD and as multiple instances of Bernoulli filters. Additionally, the thesis presents a sequential Monte Carlo (SMC) realization of the PHD/MIB filter and an approximation in the Dempster-Shafer domain called Dempster-Shafer PHD/MIB (DS-PHD/MIB) filter, which requires a smaller number of particles than the original PHD/MIB filter. The thesis describes in detail an efficient, massively parallel implementation of the DS-PHD/MIB filter and outlines the algorithm in pseudo code. Finally, the thesis describes characteristics of the DS-PHD/MIB filter and discusses its advantages and disadvantages compared to object-based tracking approaches using practical application examples. A quantitative evaluation with real-world data shows that the DS-PHD/MIB filter provides consistent state estimation results and that it appropriately models the stochastic multi-object transition process and the stochastic multi-object observation process. Furthermore, the evaluation confirms the real-time capability of the parallelized implementation of the DS-PHD/MIB filter and its usefulness for state estimation of a dynamic vehicle environment.A short version of the thesis has been submitted for publication in The International Journal of Robotics Research and has been made available to the public via arXiv: Nuss, Dominik; Reuter, Stephan; Thom, Markus; Yuan, Ting; Krehl, Gunther; Maile, Michael; Gern, Axel; Dietmayer, Klaus: A random finite set approach for dynamic occupancy grid maps with real-time application. In: ArXiv e-prints, 2016. Available online at http://arxiv.org/abs/1605.02406

Neue Technologie zur direkten Fertigung sphärisch gekrümmter Gewebe

Preformen für komplex gekrümmte Schalenstrukturen für den Einsatz in faserverstärkten Kunstoffen werden aktuell meist mittels sequentiellem Preforming gefertigt, wodurch zeit- und materialaufwändige Prozessschritte notwendig sind. Um diese Arbeitsschritte zu minimieren und den hohen Bedarf seitens der Industrie an dreidimensionalen, schalenförmigen Preformen zu decken, wurde im Rahmen des IGF-Projekts 19805 BR die neuartige Technologie des abzugsfreien Webens entwickelt. Diese ermöglicht das direkte Weben sphärisch gekrümmter Strukturen komplexer Geometrie. Dominik Nuss, Quang Pham, Gerald Hoffmann, Chokri Cherif Institut für Textilmaschinen und Textile Hochleistungswerkstofftechnik (ITM), Technische Universität Dresden, Dresden</p

Opracowanie metod mających na celu poprawę właściwości mechanicznych powleczonych georusztów do zastosowań w budownictwie

This paper presents investigations aiming to improve the impregnation of a coating agent and thus increase the mechanical performance of geogrids, especially grid-like non-crimp fabrics (NCF) consisting of carbon fiber heavy tows (CFHT). The squeezing process is industry standard, but the relationship between the machine setting parameters (squeezing pressure and hardness of squeeze roll surface) and the impact on the tensile strength of grid-like NCF is still unexplored. The setting parameters evaluated lead to an increase in tensile strength of up to 10% compared to grid-like NCF coated without the squeezing process. Additionally the first insights into the coating process supported by ultrasonic vibrations based on CFHT single yarns are provided. It is shown that the tensile strength of treated CFHT can be increased by up to 12%, in comparison to CFHT coated without ultrasonic vibrations.W pracy przedstawiono badania mające na celu poprawę impregnacji środka powlekającego, a tym samym poprawę właściwości mechanicznych georusztów, w szczególności tkanin niekarbikowanych typu siatkowego (NCF) składających się z ciężkich kabli włókien węglowych (CFHT). Proces zgniatania jest standardem branżowym, ale wciąż nie zbadano związku między parametrami nastawczymi maszyny (nacisk ściskania i twardość ściśniętej powierzchni walca) a wytrzymałością na rozciąganie tkanin NCF. Odpowiednio dobrane parametry nastawcze procesu zgniatania skutkują do zwiększeniem wytrzymałości na rozciąganie do 10% w porównaniu z georusztem, który nie został poddany temu procesowi. Ponadto oceniono wpływ procesu powlekania z użyciem ultradźwięków. Stwierdzono, że wytrzymałość na rozciąganie obrobionych kabli (CFHT) można zwiększyć nawet o 12%, w porównaniu z CFHT bez zastosowania obróbki ultradźwiękami