The initiation and progression of damage in composite overwrapped pressure vessels subjected to contact loads

Abstract

In order to investigate the residual strength of composite overwrapped pressure vessels subjected to impact loads, an extensive experimental study has been performed. The vessels are loaded up to different mechanical work levels (quasi-static) or with various impact energies (dynamic). After loading, the emerged damage in the pressure vessel is examined using computed tomography scans. The tests of vessels up to various energies enable us to visualize the initiation and progressive growth of damage. The overall influence of the damage is subsequently quantified by means of a burst pressure test. Accordingly, the reduction of burst pressure can be used to evaluate the global severity of the observed damage in the computed tomography scan. From the experiments, it is concluded that the first failure mechanisms, that is, delaminations, do not cause a meaningful reduction of the burst pressure. Shear bands, on the other hand, which are formed thereafter, do induce a significant decrease of the residual strength.

The influence of the internal pressure on the residual strength of composite-overwrapped pressure vessels subjected to external contact loading

“…The results for quasi-statically tested unpressurized vessels presented in [2] are included to validate the experimental setup, and to enable a comparison of the results between pressurized vessels and unpressurized ones. The tests are summarized in Table 2 and are normalized using the same factors as the pressurized vessels in Table 1.…”

“…The studied pressure vessel is identical to the one presented in [2]. It is a commercial type IV pressure vessel with an inner volume of 36 liters and is schematically shown in Fig.…”

“…External contact loading was applied in a similar manner as in previous studies [2,12]: The pressure vessel is locally loaded at its center using a cubic-shaped indenter, which is translated slowly. The indenter has external dimensions of 100 × 100 mm and the contact edges are rounded with a 5 mm radius to prevent local cutting of the vessel's surface.…”

“…After external contact loading, the internal pressure was released and the pressure vessels were subsequently studied using computed tomography (CT) using the same setup as used in [2]. The scans were performed at the Institute of Lightweight Engineering and Polymer Technology, Technical University of Dresden.…”

“…To further improve the safety of pressure vessel use, its damage tolerance under impact conditions needs to be well understood. Therefore, we previously performed an experimental study of unpressurized pressure vessels under impact conditions [2]. It was shown that the main failure mechanism consists of delamination initiation which does not noticeably affect the residual burst pressure, followed by shear band growth which does induce a significant reduction of the burst pressure.…”