Filtern
Dokumenttyp
- Vortrag (18)
- Zeitschriftenartikel (9)
- Beitrag zu einem Tagungsband (6)
- Posterpräsentation (2)
- Forschungsbericht (1)
Schlagworte
- Composite (10)
- Composite cylinder (7)
- Cylinder (7)
- Regulations (5)
- Probabilistic (4)
- GTR 13 (3)
- Hydrogen (3)
- Pressure (3)
- Slow burst test (3)
- Statistics (3)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (18)
Hydrogen is an attractive energy carrier that requires high effort for safe storage. For ensuring safety, they must undergo a challenging approval process. Relevant standards and regulations for composite cylinders used for the transport of hydrogen and for its onboard storage are currently based on deterministic (e.g. ISO 11119-3) or semi-probabilistic (UN GTR No. 13) criteria. This paper analysis the properties of such methods with respect to the evaluation of load cycle strength. Their characteristics are compared with the probabilistic approach of the BAM. Based on Monte-Carlo simulations, the available design range (mean value and scatter of strength criteria) of current concepts was exemplarily estimated. The aspect of small sample sizes is analysed and discussed with respect to the evaluation procedures.
Ein statistischer Bewertungsansatz für Technologien oder Produkte erfordert die Festlegung definierter Grenzwerte für die Mindestzuverlässigkeit, um die Wahrscheinlichkeit eines kritischen Versagens auf einem akzeptablen Niveau bewerten zu können. Dabei gestaltet sich sowohl die Definition akzeptierter Technologierisiken als auch die Ermittlung der tatsächlichen Risiken auf der Basis von Eintrittswahrscheinlichkeit und der Konsequenz eines Versagens stets komplex. Am Beispiel des statistischen Ansatzes der BAM zur Sicherheitsbeurteilung von Composite-Druckgefäßen wird das definierte Sicherheitsniveau und die zu erwartenden Konsequenzen ermittelt und bestehenden Akzeptanzgrenzen gegenübergestellt.
The application range of CPV (composite pressure vessels)
is multifaceted. But also the failure forms and the spectrum of measurement methods is manifold. On various, at BAM observed effects, it is shown why the micromechanical analysis of the composites is of such great interest for the prediction of aging effects of CPVs.
The application of composite pressure vessels is of great interest due to tremendous weight saving. Nevertheless, ageing of CFRP (carbon fiber reinforced plastic) composites pressure vessels underlies complex interactions between metallic liner and composite and is not fully understood yet. One main challenge is the application of appropriate testing methods for detecting the influences of pressure cycles and creep behavior on the material. This contribution presents results achieved by using conventional eddy current testing (ET) and high frequency ET. Here, we could show that also conventional ET with low frequencies are useable to investigate pressure vessels of different material combinations like aluminum-CFRP and synthetics-CFRP.
The use of composite pressure vessels instead of conventional vessels made of steel or aluminum grew strongly over the last decade. The reason for this trend is the tremendous weight saving in case of composite vessels. However, the long-time behavior is not fully understood for filling and discharging cycles and creep strength and their influence on the CFRP coating (carbon fiber reinforced plastics) and the internal liner (steel, aluminum, or plastics). The CFRP ensures the pressure resistance while the inner liner is used as container for liquid or gas. To overcome the missing knowledge of ageing BAM started an internal project to investigate degradation of these material systems. Therefore, applicable testing methods like eddy current testing are needed. Normally, high-frequency eddy current testing (HF-ET, f > 10 MHz) is deployed for CFRP due to its low conductivity of the fiber, which is in the order of 0.01 MS/s, and the capacitive coupling between the fibers. Nevertheless, in some cases conventional ET can be applied. We show a concise summary of studies on the application of conventional ET of composite pressure vessels.
Composite materials show a degradation of properties depending on Service life. This creates the necessity to find tailored methods to determine strength and residual strength of composite cylinders. The determination can be done e.g. by load cycles tests. The result needs a Statistical assessment for the precise description of strength. Especially the Statistical assessment of load cycle strength properties has a high uncertainty. It is unclear if a Log-Normal distribution, a WEIBULL distribution or others, describe the scatter behaviour of residual strength properties correctly. Distribution functions aim at approximating the frequency of occurrence of residual load cycle strength for high survival rates. An assumption has to be found and confirmed to prevent overestimation of reliability.