5 Werkstofftechnik
Filtern
Dokumenttyp
- Vortrag (52)
- Zeitschriftenartikel (41)
- Posterpräsentation (15)
- Beitrag zu einem Tagungsband (14)
- Dissertation (4)
- Beitrag zu einem Sammelband (2)
- Forschungsdatensatz (2)
- Sonstiges (1)
Sprache
- Englisch (99)
- Deutsch (31)
- Mehrsprachig (1)
Schlagworte
- Fatigue (15)
- Glass fiber reinforced polymers (9)
- Composite (6)
- Environmental stress cracking (6)
- Full Notch Creep Test (6)
- Sandwich (6)
- Wind turbine blades (6)
- Diesel (5)
- Environmental stress cracking (ESC) (5)
- Fracture (5)
- High-density polyethylene (5)
- Mikroplastik (5)
- Polymer matrix composites (5)
- Betriebsfestigkeit (4)
- Environmental Stress Cracking (4)
- Full-Notch Creep Test (FNCT) (4)
- Microplastics (4)
- Non-destructive testing (4)
- PE-HD (4)
- Polymer (4)
- Scarf repairs (4)
- Self-healing (4)
- TED-GC-MS (4)
- Thermomechanics (4)
- X-ray refraction (4)
- Biodiesel (3)
- CFK (3)
- Carbon Fiber Reinforced Plastics (3)
- Carbon fibres (3)
- Composites (3)
- Crack Propagation (3)
- Crack evolution (3)
- Degradation (3)
- Diffraction Enhanced Imaging (3)
- Ermüdung (3)
- Fracture surface analysis (3)
- Full notch creep test (FNCT) (3)
- GFRP (3)
- In situ tensile test (3)
- Infrarotspektroskopie (3)
- Interfacial strength (3)
- Laser scanning microscopy (LSM) (3)
- Lightweight materials (3)
- Luftultraschall (3)
- Mechanical properties (3)
- Polyethylene (3)
- Pulveraktivkohle (3)
- Rotor blade (3)
- Röntgenrefraktion (3)
- Slow crack growth (SCG) (3)
- Temperature (3)
- Thermogravimetrie (3)
- UV-irradiation (3)
- Wind energy (3)
- Wind turbine blade shells (3)
- Windenergie (3)
- Air-coupled ultrasonic testing (2)
- Airborne ultrasonic testing (2)
- Analysis (2)
- Belebtschlamm (2)
- Crack propagation analysis (2)
- Crop protection products (2)
- Cross linking (2)
- Cure process (2)
- Damage (2)
- Dynamic mechanical analysis (DMA) (2)
- Environmental Stress Cracking (ESC) (2)
- Epoxy (2)
- Erneuerbare Energien (2)
- Faser-Kunststoff-Verbunde (2)
- Faserkunststoffverbunde (2)
- Fatigue of sandwich shell structures (2)
- Ferroelectret (2)
- Ferroelektret (2)
- Fiber reinforced polymer (2)
- Fracture Surface Analysis (2)
- GFK (2)
- Interface (2)
- Interfacial shear strength (2)
- Kavitation (2)
- Laminography (2)
- Long-term storage (2)
- Mikrostruktur (2)
- Photon counting detector (2)
- Polyethylen (2)
- Polyethylen hoher Dichte (2)
- Polyethylene, PE-HD (2)
- Polymer Matrix Composites (2)
- Push-out Test (2)
- Recycling (2)
- Residual stresses (2)
- Rissentwicklung (2)
- Rotorblattschalen (2)
- Röntgen-Refraktion (2)
- Röntgenbeugung (2)
- Schädigung (2)
- Sorption (2)
- Spannungsriss (2)
- Synchrotronstrahlung (2)
- Thermoanalyse (2)
- Thermogravimetry (2)
- Thermomechanik (2)
- Thermoplastic (2)
- Thermoset polymers (2)
- Wandler (2)
- Wind turbine (2)
- X-ray computed tomography (CT) (2)
- X-ray laminography (2)
- Abwasser (1)
- Advanced wastewater treatment (1)
- Alterung (1)
- Alumina (1)
- Analyse (1)
- Analytik (1)
- BTEX (1)
- Bacterial attachment (1)
- Bilanzierung (1)
- Biopolymer (1)
- Boden (1)
- Brittle / ductile fracture behavior (1)
- Brittle fracture (1)
- Bruchflächenanalyse (1)
- Bruchflächenauswertung (1)
- C. lap-shear (1)
- CFRP (1)
- Carbon Fibers (1)
- Carbon Fibre (1)
- Carbon fibre-reinforced-plastics (1)
- Carbon nanotubes (1)
- Cavitation (1)
- Cellulose (1)
- Ceramic spring (1)
- Ceramic springs (1)
- Certification Standard 22 (1)
- Chemometrics (1)
- Chemometrie (1)
- Chromatography (1)
- Coating (1)
- Composite recycling (1)
- Composite structures (1)
- Composite testing (1)
- Cooling rate (1)
- Crack growth (1)
- Crack opening displacement (1)
- Crack propagation (1)
- Craze-crack mechanism (1)
- Craze–crack mechanism (1)
- Creep (1)
- Critical energy release rate (1)
- Crop protection formulations (1)
- Cryogenic (1)
- Crystal Texture (1)
- D. aging (1)
- D. creep D. viscoelasticity (1)
- Damage evolution (1)
- Damage mechanisms (1)
- Data Management (1)
- Data Structures (1)
- Debonding (1)
- Deformation behavior (1)
- Degradation signatures (1)
- Dentine (1)
- Desorption (1)
- Diesel Fuel (1)
- Digitalisierung (1)
- Distributed fiber optic sensing (1)
- Distributed fiber optic sensors (1)
- Distributed fibre optic sensors (1)
- Dual-energy (1)
- EASA (1)
- Elastic properties (1)
- Electric conductivity (1)
- Enamel (1)
- Epoxidharz (1)
- Epoxy Resin (1)
- Epoxy resin (1)
- FNCT (1)
- Failure mechanisms (1)
- Faser (1)
- Faser-Kunststoff-Verbund (1)
- Faserverstärkte Kunstoffe (1)
- Fatigue Life Evaluation (1)
- Fatigue Testing (1)
- Fatigue of sandwich structures (1)
- Fiber reinforced polymers (1)
- Fiber-matrix interface (1)
- Fiber/matrix bond (1)
- Fibre reinforced plastic (1)
- Fibre/matrix bond (1)
- Fibre/matrix bonding (1)
- Force-distance diagram (1)
- Four-point bending test (1)
- Fourier transform infrared spectroscopy (1)
- Fracture behavior (1)
- Fracture surface (1)
- Fracture surfaces (1)
- Fracture toughness (1)
- Fuel sorption (1)
- Full Notch Creep Test (FNCT) (1)
- Full notch creep test (1)
- Full-Notch Creep Test (1)
- Full-notch creep test (1)
- GC-MS (1)
- General Aviation (1)
- Geometrical factors (1)
- Glas fibre reinforced polymer (1)
- Glasfaserverstärkter Kunststoff (1)
- Glass Fibres (1)
- Glass capillaries (1)
- Glass fiber reinforced polymer (1)
- Glass fiber-epoxy composites (1)
- Glass fibre (1)
- Glass fibre reinforced plastics (1)
- HDPE Soprption (1)
- HDPE Sorption (1)
- High density polyethylene (1)
- High-density polyethylene (PE-HD) (1)
- High-temperature properties (1)
- Hydrogel (1)
- Hydrogen storage (1)
- Hydrothermal Ageging (1)
- Hygrothermal (1)
- Imaging (1)
- Imaging techniques (1)
- Indentation hardness (1)
- Initial attachment (1)
- Interface Strength (1)
- Interfacial Strength (1)
- Intermediate scale (1)
- Internal Surfaces (1)
- Interphase (1)
- Joints/joining (1)
- Keywords: Poly(ether ether ketone) (1)
- Klebung (1)
- Knowledge Representation (1)
- Komponentenprüfung (1)
- Kurzfaser-verstärkte Thermoplaste (1)
- Laminographie (1)
- Laser Scanning Microscopy (LSM) (1)
- Laserscanningmikroskopie (LSM) (1)
- Light curing (1)
- Lightweighting (1)
- Linear elastic fracture mechanics (1)
- Long-term calculation (1)
- Lösungsmittel (1)
- Manufacturing (1)
- Masterschädigungslinie (1)
- Material degradation (1)
- Material failure (1)
- Materialmodell (1)
- Materialwissenschaft (1)
- Matrix (1)
- Matrix residual stress (1)
- Mechanical and thermal testing (1)
- Mechanical deformation (1)
- Microstructural orientation (1)
- NDT (1)
- Nahinfrarotspektroskopie (1)
- Natural (1)
- Near Infrared Spectroscopy (1)
- New standards (1)
- Nondestructive testing (1)
- Normung (1)
- Oberflächenaktive wässrige Medien (1)
- Ontology (1)
- Optical backscatter reflectometry (1)
- Optical criterion (1)
- Optical criterion of brittleness (1)
- Optical fibre (1)
- Orientation-dependent microstructure (1)
- PA6.6 (1)
- PE-HD Sorption (1)
- PLS-DA (1)
- PPA (1)
- Packaging (1)
- Permeability (1)
- Phase transformation (1)
- Photocleavable organosilanes (1)
- Photopolymer composites (1)
- Phytolith (1)
- Plasma nanocoatings (1)
- Plasticity (1)
- Polymer Matrix Composite (1)
- Polymer analysis/characterization (1)
- Polymer composite (1)
- Polymer-matrix composites (PMC) (1)
- Polymerwissenschaften (1)
- Polymer–matrix composites (1)
- Polyolefins (1)
- Polypropylene (1)
- Polystyrene (1)
- Powdered activated carbon (1)
- Pull-out (1)
- Pull-out composite materials (1)
- Pultruded fiber rods (1)
- Renewable ernergy (1)
- Repair of sandwich shell structures (1)
- Repair patch (1)
- Rohrprobekörper (1)
- Rotorblatt (1)
- Rotorblätter (1)
- Sailplane Development Panel (1)
- Sandwich structures (1)
- Sandwichstruktur (1)
- Scanning Electron Microscopy (SEM) (1)
- Scanning acoustic microscopy (SAM) (1)
- Scarf joint (1)
- Scarf joint repair (1)
- Scarf joint repairs (1)
- Schalenprüfstand (1)
- Semantic Web Technologies (1)
- Sewage treatment plant (1)
- Short-beam strength (1)
- Single fiber pull-out test (1)
- Slow Crack Growth (SCG) (1)
- Slow crack growth (1)
- Smart materials (1)
- Soil (1)
- Soil sample (1)
- Spar cap design (1)
- Stress intensity factor (1)
- Structural composites (1)
- Structural health monitoring (1)
- Structural health monitoring (SHM) (1)
- Support vector machines (1)
- Surface modification (1)
- Surface treatments (1)
- Swept wavelength interferometry (1)
- Swept wavelength interferometry (SWI) (1)
- Synthesis (1)
- TED (1)
- Test Improvement (1)
- Thermal cycling (1)
- Thermal degradation (1)
- Thermal desorption mass spectrometry (1)
- Thermische Analyse (1)
- Thermo mechanical fatigue (1)
- Thermo-mechanical-loading (1)
- Thermo-mechanics (1)
- Thermoanalysis (1)
- Thermographie (1)
- Thermoplastic matrix (1)
- Thermoplastic prepreg (1)
- Thermoset composition (1)
- Thermosetting resin (1)
- Tooth wear (1)
- Transducers (1)
- Umgebungsbedingter Spannungsriss (1)
- Unidirectional composites (1)
- Verbundwerkstoffe (1)
- Very high cycle fatigue (1)
- Viscoelastic model (1)
- Volatiles from thermosets (1)
- WAXS (1)
- Waste water (1)
- Water Diffusion (1)
- Werkstoffdaten (1)
- Werkstoffprüfung (1)
- Wind turbine blade shell structures (1)
- Windkraft (1)
- Work of adhesion (1)
- X-ray refractography (1)
- ZfP (1)
- Zirconia (1)
- Zug-Druck-Schubprüfung (1)
- multi scale testing (1)
- thermomechanische Beanspruchung (1)
Organisationseinheit der BAM
- 5.3 Polymere Verbundwerkstoffe (131) (entfernen)
Paper des Monats
- ja (1)
Eingeladener Vortrag
- nein (52)
Um den sicheren Betrieb von Windkraftanlagen zu gewährleisten, werden Rotorblätter nach der Fertigung und nach Reparatur mit verschiedenen zerstörungsfreien Verfahren auf Schaden untersucht. Bei der Fertigung von Blattschalen, die in einer Sandwich-Schalenbauweise gefertigt werden, entstehen Imperfektionen, die unter Belastung zu großen Rissen führen können. Zur Prüfung von Blattschalen wird unter anderem Ultraschallprüfung in Kontakttechnik eingesetzt. Um den Wartungsaufwand von Ultraschallanlagen zu reduzieren und um manche Kompositstrukturen vor Koppelmittel zu schützen, wird die Anwendung von Luftultraschall erforscht. Insbesondere große Fortschritte gibt es im Bereich der Entwicklung neuer Wandler.
In diesem Beitrag berichten wir über die Luftultraschallprüfung von Schalen für Rotorblätter. Es wurden typische Sandwichschalenstrukturen hergestellt und mit einem eigenentwickelten Schalenprüfstand unter simulierter Betriebsbeanspruchung belastet. Die in den Schalenprüfkörpern entstandenen Schäden wurden außerhalb des Prüfstandes mit Luftultraschall in Durchschallung untersucht. Es wurden fokussierende Wandler auf Basis von Ferroelektreten entwickelt und für diese Prüfungen eingesetzt. Mit zusätzlicher elektrischer Vorspannung konnte die Empfindlichkeit der Empfänger deutlich erhöht werden. Die nach dem Lastwechsel entstandenen Schäden in den Rotorblattschalen waren eindeutig zu detektieren.
Um den sicheren Betrieb von Windkraftanlagen zu gewährleisten, werden Rotorblätter nach der Fertigung und nach Reparatur mit verschiedenen zerstörungsfreien Verfahren auf Schaden untersucht. Bei der Fertigung von Blattschalen, die in einer Sandwich-Schalenbauweise gefertigt werden, entstehen Imperfektionen, die unter Belastung zu großen Rissen führen können. Zur Prüfung von Blattschalen wird unter anderem Ultraschallprüfung in Kontakttechnik eingesetzt. Um den Wartungsaufwand von Ultraschallanlagen zu reduzieren und um manche Kompositstrukturen vor Koppelmittel zu schützen, wird die Anwendung von Luftultraschall erforscht. Insbesondere große Fortschritte gibt es im Bereich der Entwicklung neuer Wandler.
In diesem Beitrag berichten wir über die Luftultraschallprüfung von Schalen für Rotorblätter. Es wurden typische Sandwichschalenstrukturen hergestellt und mit einem eigenentwickelten Schalenprüfstand unter simulierter Betriebsbeanspruchung belastet. Die in den Schalenprüfkörpern entstandenen Schäden wurden außerhalb des Prüfstandes mit Luftultraschall in Durchschallung untersucht. Es wurden fokussierende Wandler auf Basis von Ferroelektreten entwickelt und für diese Prüfungen eingesetzt. Mit zusätzlicher elektrischer Vorspannung konnte die Empfindlichkeit der Empfänger deutlich erhöht werden. Die nach dem Lastwechsel entstandenen Schäden in den Rotorblattschalen waren eindeutig zu detektieren.
3D structural investigations are described by X-ray laminography studies of sandwich shell segments, made of a PVC foam core, covered by non-crimp fabric glass fibre composite lay-ups processed by vacuum assisted resin infusion of epoxy. The specific scope of this study is to image transversal flaws within the foam core (joints) and of single ply overlaps. Test flaws were purposely implemented in order to simulate typical failure under cyclic load. In a dedicated test rig for shell structures, the flaw evolution/propagation is monitored by thermography and optical 3D inspection of deformation. Due to the unfavourable preconditions for classical computed tomography as of large aspect ratio, the samples were investigated by coplanar translational laminography. Its limited range of observation angles of ± 45°, results in anisotropic artefacts about the normal to the sample surface, but the typical flaws are well visualized in the as-prepared state, in a state of early damage, and in the repaired state.
Motivation:
> Zunehmender Einsatz von Pulveraktivkohle (PAK) zur
Spurenstoffelimination in kommunalen Kläranlagen
> Bisher keine analytische Methode zur Quantifizierung von PAK in
Belebungsbecken, bzw. in Gegenwart von Belebtschlamm
> Anwendung der Thermogravimetrischen Analyse (TGA) zur
Feststoffcharakterisierung auf Umweltfragestellungen
Ergebnisse:
> Quantifizierung von PAK in Belebtschlamm ist möglich und kann
über unterschiedliche zweistufige TGA-Methoden erfolgen
> Zersetzungsgasanalyse zeigt veränderte und verzögerte
Freisetzung aliphatischer Produkte des Belebtschlamms
Advanced wastewater treatment with powdered activated carbon (PAC) leads to a spread of PAC into different purification stages of wastewater treatment plants (WWTP) due to recirculation and filter back-wash. Currently, no methods for quantification of PAC in activated sludge are available. In this study, PAC containing activated sludge from four WWTP were examined by two-step thermogravimetric analysis (TGA) with heating up to 600°C in N2 and subsequently in synthetic air. Direct quantification of PAC according to temperature specific weight losses was possible for one WWTP. Quantification by combining specific mass losses was found to be an alternative direct method, with a detection limit of 1.2% PAC in dry sample mass.
Additionally, evolved gas analysis (EGA) by infrared-spectroscopy (FTIR) during TGA revealed interaction mechanisms between PAC and activated sludge. Aliphatic compounds from activated sludge were identified as major substances influenced by PAC. In derivative thermogravimetry (DTG), a typical double peak at approximately 300°C was found to be related to carbonylic species with increased evolution of acetic acid in aged activated sludge. TGA and EGA are promising tools to understand, control and optimise the application of PAC in advanced wastewater treatment.
The presence, fate and effects of microplastics (MP) in terrestrial systems are largely unknown. The few existing studies investigated either agricultural or industrial sites. Several techniques were used for analysis, primarly spectroscopic methods such as FTIR or Raman. Sample pretreatments like density separations are common to reduce matrix. A lack of harmonised and standardised sampling instructions for microplastic investigations in the terrestrial area was identified as particular critical, because different studies are barely comparable.
The aim of the project is to develop a proposal for a harmonized procedure for sampling, sample preparation and the detection of microplastics in terrestrial matrices for total content determination. By detecting specific degradation products the thermal extraction desorption gas chromatography mass spectrometry (TED-GC-MS) allows a direct determination of mass content of MP in environmental samples.
As the well-known damage mechanisms slow crack growth (SCG) and environmental stress cracking (ESC) are the major causes for possible failure of polyolefin-based materials, especially for PE-HD, they are highly relevant and need to be considered thoroughly. Furthermore, due to slight but perceptible differences in damaging effect, a differentiation between SCG and ESC is expedient. SCG appears in “inert” or “neutral” media without a decisive influence of the surrounding medium whereas ESC occurs in “active” media, which influence the failure behavior and time to failure crucially.
To characterize the inherent resistance of the material against those damage mechanisms, the well-established Full-Notch Creep Test (FNCT) is used. In this study, the FNCT – usually applied according to ISO 16770 [3] using a few universal model liquid media and mainly for pipe materials – is extended by investigations with appropriate parameters of selected relevant PE-HD container materials also in real media, such as the topical fuels diesel and biodiesel. The investigations were performed using a novel FNCT-device with 12 individual sub-stations, each equipped with individual electronic stress and temperature control and continuous online monitoring of the specimen elongation.
Especially, mechanical stress and temperature were varied systematically during FNCT and time to failure values, time-dependent elongation data as well as detailed fracture surface analysis by laser scanning microscopy (LSM) were combined for the first time (Fig. 1). Particularly, the fracture surface analysis provides a sound basis to characterize failure behavior, mainly regarding the balance between brittle crack propagation and ductile deformation. Therefore, fracture surface analysis is an essential tool for a decent assessment of SCG and ESC by FNCT measurements.
Tooth wear induced by abrasive particles is a key process affecting dental function and life expectancy in mammals. Abrasive particles may be plant endogenous opal phytoliths, exogene wind-blown quartz dust or rain borne mineral particles ingested by mammals. Nano-indentation hardness of abrasive particles and dental tissues is a significant yet not fully established parameter of this tribological system. We provide consistent nano-indentation hardness data for some of the major antagonists in the dental tribosystem (tooth enamel, tooth dentine and opaline phytoliths from silica controlled cultivation). All indentation data were gathered from native tissues under stable and controlled conditions and thus maximize comparability to natural systems. Here we show that native (hydrated) wild boar enamel exceeds any hardness measures known for dry herbivore tooth enamel by at least 3 GPa. The native tooth enamel is not necessarily softer then environmental quartz grit, although there is little overlap. The native hardness of the tooth enamel exceeds that of any silica phytolith hardness recently published. Further, we find that native reed phytoliths equal native suine dentine in hardness, but does not exceed native suine enamel. We also find that native suine enamel is significantly harder than dry enamel and dry phytoliths are harder than native phytoliths. Our data challenge the claim that the culprit of tooth wear may be the food we chew, but suggest instead that wear may relates more to exogenous than endogenous abrasives.
A shell test bench was developed at BAM 5.3 which allows for static and fatigue testing of curved fiber-reinforced plastic (FRP) structures, during which in-situ the damage state can be non-destructively inspected by thermography and strain-field measurement techniques. Sandwich shell specimens with typical wind turbine blade manufacturing defects were designed and tested. The tested imperfections show a fairly significant reduction (up to 90%) of the shell test specimens‘ lifetime, depending on the type of imperfection. Using the in-situ NDT methods incorporated in the shell test bench, the location and cycle time of the initial defects and the damage evolution was investigated.
A shell test bench was developed at BAM 5.3 which allows for static and fatigue testing of curved fiber-reinforced plastic (FRP) structures, during which in-situ the damage state can be non-destructively inspected by thermography and strain-field measurement techniques. Sandwich shell specimens with typical wind turbine blade manufacturing defects were designed and tested. The tested imperfections show a fairly significant reduction (up to 90%) of the shell test specimens‘ lifetime, depending on the type of imperfection. Using the in-situ NDT methods incorporated in the shell test bench, the location and cycle time of the initial defects and the damage evolution was investigated.
The described investigation of carbon-fibre-reinforced plastics (CFRP) documents that damage evolution can be observed by means of X-ray refractography. Comparative investigations with synchrotron technique on CFRP and grey-scale analysis on glass fibre-reinforced-plastics (GFRP) confirm these results. Moreover it was found that the fracture mechanical properties of the matrix system influence damage nucleation and propagation in the laminate during static and fatigue loads. Single-step fatigue tests were carried out on Laminates with RIM135 and LY556 matrix systems made from non-crimped fabric (NCF) or twill weave in different fibre orientations. The damage to the LY556 laminates was characterized by laminate cracks growing rapidly over the whole specimen width, whereas the damage on the RIM135 laminates was characterized by an earlier onset of micro-cracking followed by laminate cracks. The specimens were fatigued up to 108 (very high cycle fatigue (VHCF) regime) load cycles. S-N-curves of damage initiation were drawn and boundaries were identified for endurance within the VHCF regime. A phenomenology based model focusing on matrix stress was applied to reproduce the first inter-fibre failure (IFF) under static and fatigue loads.
Fiber-reinforced-polymers (FRPs) are in current research focus in the lightweight construction industry, because of their extraordinary characteristics (stiffness and strength-to-density relation). The structure of polymer matrix and the interaction with reinforcement are crucial for optimization of the mechanical and thermal properties of FRPs. Due to the macromolecular chain structure, the mechanical properties of a polymer strongly vary with temperature: Below the glass transition, the chain segments of a polymer are “frozen”. Regarding fracture, the total changed energy during fracture if only dissipates for the generation of the new surfaces. However, in the region of the glass transition, the polymer chain segments start to get “unfrozen”, and the energy is not only required for generating new surfaces, but also for irreversibly deformation. This irreversible deformation is affected by the global temperature and the local temperature near the crack tip, which is affected by the local strain rate and crack propagation velocity.
Hence, in this research project, the irreversible deformation of neat and reinforced polymers will be controlled by changing the global temperature as well as the local temperature. With using different fracture experiments, the amount of energy required for creating new surfaces and for the irreversible deformation will be separated. The fracture tests include the conventional tensile test, the macroscopic peel test and the single fiber peel – off test.
Different imaging techniques were employed to monitor Full Notch Creep Test (FNCT) experiments addressing environmental stress cracking in more detail. The FNCT is a well-established test method to assess slow crack growth and environmental stress cracking of polymer materials, especially polyethylene. The standard test procedure, as specified in ISO 16770, provides a simple comparative measure of the resistance to crack growth of a certain material based on the overall time to failure when loaded with a well-defined mechanical stress and immersed in a liquid medium promoting crack propagation.
Destructive techniques which require a direct view on the free fracture surface, such as light microscopy and laser scanning microscopy, are compared to non-destructive techniques, i.e. scanning acoustic microscopy and xray micro computed tomography. All methods allow the determination of an effective crack length. Based on a series of FNCT specimens progressively damaged for varied Durations under standard test conditions, the estimation of crack propagation rates is also enabled. Despite systematic deviations related to the respective Imaging techniques, this nevertheless provides a valuable tool for the detailed evaluation of the FNCT and its further development.
Common air-coupled transducers for non-destructive testing consist of a piezocomposite material and several matching layers. Better acoustical matching to air is achieved by transducers based on charged cellular polypropylene (PP). This material has about hundred times lower acoustic impedance than any piezocomposite, having about the same piezoelectric coefficient. The piezoelectric properties of cellular PP are caused by the polarization of air cells. Alternatively, a ferroelectret receiver can be understood as a capacitive microphone with internal polarization creating permanent internal voltage. The sensitivity of the receiver can be increased by applying additional bias voltage. We present an ultrasonic receiver based on cellular PP including a high-voltage module providing bias voltage up to 2 kV. The application of bias voltage increased the signal by 12 to 15 dB with only 1 dB increase of the noise.
This receiver was combined with a cellular PP transmitter in through transmission to inspect several test specimens consisting of glass-fiber-reinforced polymer face sheets and a porous closed-cell PVC core. These test specimens were inspected before and after load. Fatigue cracks in the porous PVC core and some fatigue damage in the face sheets were detected. These test specimens were originally developed to emulate a rotor blade segment of a wind power plant. Similar composite materials are used in lightweight aircrafts for the general aviation. The other inspected test specimen was a composite consisted of glass-fiber-reinforced polymer face sheets and a wooden core. The structure of the wooden core could be detected only with cellular PP transducers, while commercial air-coupled transducers lacked the necessary sensitivity. Measured on a 4-mm thick carbon-fiber-reinforced polymer plate, cellular PP transducers with additional bias voltage achieved a 32 dB higher signal-to-noise ratio than commercial air-coupled transducers.
Common air-coupled transducers for non-destructive testing consist of a piezocomposite material and several matching layers. Better acoustical matching to air is achieved by transducers based on charged cellular polypropylene (PP). This material has about hundred times lower acoustic impedance than any piezocomposite, having about the same piezoelectric coefficient. The piezoelectric properties of cellular PP are caused by the polarization of air cells. Alternatively, a ferroelectret receiver can be understood as a capacitive microphone with internal polarization creating permanent internal voltage. The sensitivity of the receiver can be increased by applying additional bias voltage. We present an ultrasonic receiver based on cellular PP including a high-voltage module providing bias voltage up to 2 kV. The application of bias voltage increased the signal by 12 to 15 dB with only 1 dB increase of the noise.
This receiver was combined with a cellular PP transmitter in through transmission to inspect several test specimens consisting of glass-fiber-reinforced polymer face sheets and a porous closed-cell PVC core. These test specimens were inspected before and after load. Fatigue cracks in the porous PVC core and some fatigue damage in the face sheets were detected. These test specimens were originally developed to emulate a rotor blade segment of a wind power plant. Similar composite materials are used in lightweight aircrafts for the general aviation. The other inspected test specimen was a composite consisted of glass-fiber-reinforced polymer face sheets and a wooden core. The structure of the wooden core could be detected only with cellular PP transducers, while commercial air-coupled transducers lacked the necessary sensitivity. Measured on a 4-mm thick carbon-fiber-reinforced polymer plate, cellular PP transducers with additional bias voltage achieved a 32 dB higher signal-to-noise ratio than commercial air-coupled transducers.
Glass-fibre-reinforced plastics (GFRP) are commonly used for the construction of pressure vessels and tanks for example in automotive and aerospace industries. Especially for pressure vessels used for the storage of natural gas or hydrogen with operation pressures up to 700 bar, an early material fatigue detection is of great interest. Measuring the distributed strain profile of GFRP structures helps to understand and detect material fatigue. In this article, we demonstrate the great potential of swept wavelength interferometry (SWI) based distributed strain sensing for the monitoring of pressure vessels made from GFRP. A resin transfer molding (RTM) process was used to manufacture GFRP-tube specimens. Commercial optical fibres with polyimid coating were glued to the surface externally in circumferential and axial direction. A cyclic load of up to 150 bar was applied to the samples using a servo-hydraulic test bench. Comparing the loaded and unloaded test conditions, we determined up to 2 % elongation in circumferential direction. We demonstrate reliable distributed strain measurements with sub-centimetre spatial resolution. By monitoring these high-resolution strain profiles, we were able to detect local material degradation that manifested itself as localized strain changes. Crucially, the material Degradation could be detected already after 75 % of dat the fatigue life before a crack appeared that led to leakage.
The first documentation of fuel biodeterioration dates back to the late 19th century. However, extensive studies concerning the microbial fuel contamination started in 1980’s. Polymeric fuel storage tanks containing diesel and biodiesel provide environmental conditions for microbial growth. Several studies demonstrated that bacteria, which were found in contaminated fuel systems, can use fuels as macronutrient; but such bacteria can also cause microbiologically influenced corrosion and fouling.
The aim of this study is to investigate the initial attachment behavior of bacteria, isolated from a diesel contamination, on neat and photooxidized high-density polyethylene (PE-HD). Two common PE-HD’s, less- and biodiesel-stabilized, were radiated to UV light representing a tank exposed to sunlight. The effect of photooxidiation on PE-HD’s surface were characterized chemically by Fourier-transform infrared spectroscopy (FTIR). The attached bacteria Pseudomonas aeruginosa and Bacillus subtilis on the polymer surface were evaluated by fluorescence microscopy and colony-forming unit tests (CFU).
PE-HD as a polymeric fuel storage tank material: Photooxidation, fuel sorption and long-term storage
(2018)
High-density polyethylene (PE-HD) is a commodity thermoplastic polymer which is typically used for packing of dangerous goods. Its good resistance against photooxidation, fuels, chemicals and other environmental factors in addition to low production costs makes PE-HD attractive for fuel storage applications. Typical engine fuels stored in polymer tanks are petrol, diesel and biodiesel that receives increasing attention as proper alternative to fossil fuels. One of the major problems with biodiesel is its susceptibility to oxidize due to its chemical composition of unsaturated fatty acids which also can cause polymer degradation.
The aim of this study is to investigate the influence of different environmental factors, UV radiation and commonly stored fuels, on the mechanical, physical and chemical properties of two types of PE-HD polymers (stabilized and non-stabilized). The influence on the mechanical properties was tested by Charpy and tensile tests, chemical and physical properties were evaluated by Fourier-transform infrared spectroscopy (FTIR) and by dynamical mechanical analysis (DMA) tests. Samples were characterized after varying exposure time of UV radiation and after fully and partially immersion in biodiesel. In addition, similar experiments were conducted using diesel for comparison.