Tony Weber

Concrete Under High Strain Rates: Local Material and Global Structure Response to Impact Loading

Impact experiments are presented in this work. In order to analyse the behaviour of concrete under high strain rates, an impact mass is dropped from the maximum height of 9 m onto square concrete slabs with a side length of 1 m. Slabs of different concrete strengths are tested, thus the behaviour of standard concrete slabs is compared to the one of high performance concrete (HPC) and ultra high performance concrete (UHPC). Furthermore, the influence of subsequent fabric reinforcement is analysed. Different measurement techniques are used during the test procedure to study the relation of local damage and global structure behaviour. For instance, photogrammetry is used for monitoring the vertical displacement during the deflection of the concrete specimen. Beside measurement technique, stamping cone and damage effects due to the impact load are evaluated. Comparing the concrete specimen with or without additional fabric reinforcement, enormous differences in resistance to impact load and in penetration of the impactor are seen.

Investigation of Concrete Slabs under Impact Load

The behaviour of concrete slabs under dynamic load such as rock fall or vehicle impact isinvestigated in this work. The aim of this study is to enlarge the knowledge concerning thesubsequent reinforcing of concrete slabs and its inuence on their behaviour under impact load.Therefore, the results of the drop tower experiments with standard concrete, high performanceconcrete (HPC) and ultra-high performance concrete (UHPC) are compared and interpreted.The analysis of the test results focuses on the qualitative evaluation of the protective e ectand on the quantitative evaluation of measurement results. Regarding the protective e ect, theinuence of the additional steel stirrup reinforcement is rather small. In contrast, the subsequentfabric reinforcement prevents the perforation of the concrete slabs. The behaviour of steel fabricand carbon fabric is compared. Although particular di erences in fracture behaviour are seen,both types of fabric reinforcement obviate total punch-through and, hence, vastly enhance theprotective performance. Comparing the stamping cones and analysing the extent of damage, theprotective capacity of di erent concrete slabs is evaluated. Within the quantitative evaluationof the measurement results, the evolution of strains and strain rates is being considered. Onthe top side of the concrete slabs, the strain is measured as tensile strain in the rst spellafter load application, turning into compressive strain later on. The evolution of strains andstrain rates indicates wave propagation. Beside the strain results, special attention is paid tothe correlation of di erent measurement techniques. The results of strain gauges, accelerometer,load cells and photogrammetry are contextualised and therefore show the change from the localmaterial behaviour to the global structure response in temporal sequence.

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.

Experimental Investigations on Integrated Conductor Paths in Fiber-Reinforced Thermoplastic Composite Structures

By the benefit of functional integration the advantages of fiber reinforced plastics (FRP) as construction material can be increased due to the possibilities of integrating sensors and actuators. In Regard to the layer-by-layer definition of the wall thickness, this class of material offers a high potential for the integration of additional smart elements within the stacking and forming process. In addition to the actual integration methods of sensors or actuators, the electrical signal transmission and contacting is of great importance for smart structures. Various approaches can be followed. On the one hand, the conductor path can be defined by means of a wire and, on the other hand, the definition of conductor paths can be accomplished by functionalized films (by means of printing technology). Within this paper, experimental investigations are intended to demonstrate the suitability of screen-printed conductor paths for the press-technical transformation of FRP structures. In addition to the variation of the screen printing material and the film material, for a material-homogeneous integration, an evaluation of a corresponding selection of materials takes place with respect to the stresses derived from the deformation-technical boundary conditions.

Multiscale characterization and testing of function-integrative fiber-reinforced composites

Abstract Smart fiber-reinforced composites, such as long fiber or textile-reinforced polymers are often functionalized by integration of piezoelectric transducers to realize sensory and actuatory tasks like condition and structural heath monitoring, energy harvesting or active vibration damping. Each of these tasks is connected with specific requirements with regard to the electromechanical behavior of the composite structure. In this chapter, several qualitative and quantitative methods including nondestructive, optical, electrical, and mechanical testing for the characterization of smart fiber-reinforced composites are described. Beyond their functionality and electromechanical performance, structural integrity and quality assurance are focused. By example of case studies, characterization of long fiber-reinforced thermoset and textile-reinforced thermoplastic polymers with specific test setup and results are shown. Novel developments in the field of sensor and actuator development and manufacture as well as integration of these functional elements into fiber-reinforced composites are presented.

Experimental and Numerical Studies on Integration Thermoplastic Composite Compatible Piezoelectric Ceramics for Actuatory Application of Cylindrical Hollow Structures

Regarding the economical use of fiber-reinforced plastics (FRP) as a construction material for structural components whose additional value caused not only in their high specific mechanical properties. Due to the layerwise structure definition of continuous fiber reinforced composites the corresponding production technologies offers a high potential for integration of additional functional elements. Past efforts to the integration of functions in fiber-reinforced composites usual provide in front of a passive use of the piezoelectric effect (eg. structural-health monitoring). Through efficient and structurally defined using of piezoceramic actuators, the planar structure topology of cylindrical hollow FRP profiles can be actively influenced. Based on experimental studies on the definition of basic concepts for the integration of thermoplastic compatible piezoceramic modules (TPM) in fiber composite tubular segments, this paper deals with the understanding and performance capabilities of such actuarical hollow frp structures. The selective excitation and manipulation of the vibration behavior of such rotationally symmetric structures serves for generation of wave effects with radial translational characteristic. The performed experimental studies on the structural behavior of active piezo integral pipe segments are abstracted and compared by means of numerical simulations using multi-physical elements.