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Computed tomography of impact damage in high-pressure vessels

Politechnika Wroclawska (WRUT) presented a poster at Materiały Polimerowe Pomerania-Plast 2016 (Miedzyzdroje, Poland). Their poster has been awarded as the most innovative product/technology.

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Participation to WHEC 2016

Partners of the project participated to the conference WHEC 2016. The coordinator, Dr. F. Nony (CEA) presented the project. The presentation can be seen here; video are available here.

New publication - Acoustic emission testing of composite overwrapped pressure vessels

The consortium published an article titled: "AE TESTING OF COPVs SUBJECTED TO MECHANICAL IMPACTS"

To reduce greenhouse gas emission as targeted in the European Energy Roadmap 2050, hydrogen energy is one among the main clean energies that have to be increased. Currently, the most adequate technology meeting the needs for hydrogen storage (lightweight, high lifetime at high pressure) is composite overwrapped pressure vessels (COPVs). These cylinders are exposed to damage occurring from mechanical impacts (drop of cylinder, drop of objects, etc.). External impacts can affect performance, even if the damage was barely visible. A complementary technique, to Visual Testing, is therefore necessary to assess the remaining performance after impact, and thus the residual lifespan.

Abstract can be downloaded here.

Presentation by NTNU at BPS2016

NTNU attended Baltic Polymer Symposium 2016 (BPS2016).
They presented fatigue modelling related work from HyPactor.

Carbon fiber composites are utilized in various applications and in some cases, such as composite overwrapped pressure vessels (COPVs), the sustained and cyclic loading are predominantly tensile. The COPVs may be exposed to low-velocity impact damage reducing their short and long-terra residual strength. Currently, no modeling approach for assessing the long-terra performance of damaged COPVs under cyclic loads has become universally accepted by the community. In this work, a finite element (FE) based analysis is proposed for modeling the reduced fatigue life prognosis after impact. The fatigue modeling aspect is focused on, damage is simply represented by notches or holes. [...]

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New publication from NTNU

sensitivity of the burst performance of impact damaged pressure vessels to material strength properties
sensitivity of the burst performance of impact damaged pressure vessels to material strength properties

“The sensitivity of the burst performance of impact damaged pressure vessels to material strength properties” publication by K. Lasn, N. P. Vedvik and A. T. Echtermeyer (NTNU).

This numerical study is carried out to improve the understanding of short-term residual strength of impacted composite pressure vessels. The relationship between the impact, created damage and residual strength is predicted by finite element (FE) analysis. The burst predictions depend largely on the strength properties used in the material models. However, it is typically not possible to measure all laminate properties on filament wound structures. Reasonable testing efforts are concentrated on critical properties, while obtaining other less sensitive parameters from e.g. literature. A parametric FE model is hereby employed to identify the critical strength properties, focusing on the cylindrical section of the pressure vessel. The model simulates an impactor strike on an empty vessel, which is subsequently pressurized until burst. Monte Carlo Simulations (MCS) are employed to investigate the correlations between strength related material parameters and the burst pressure. The simulations indicate the fracture toughness of the composite, hoop layer tensile strength and the yield stress of the PE liner as the most influential parameters for current vessel and impact configurations. In addition, the conservative variation in strength parameters is shown to have a rather moderate effect (COV ca. 7%) on residual burst pressures.

This publication is also available in open access.