Fire behaviour of hybrid filament-wound single and adhesively bonded composites tubes under static pressure

Abstract

The present work aims to experimentally investigate the fire behaviour of water-filled E glass reinforced thermoset resin hybrid filament-wound composites tubes under static pressure. Heretofore, fire endurance tests have been conducted on single and adhesively bonded tubes manufactured by CTRA Company. Furthermore, internal pressure tests until failure have been performed on the burnt single and burnt joined tubes in order to quantify their abilities to contain the fluid after being exposed to heat flux. A comparison between the pressure behaviour of exposed to fire (burnt) and non-exposed tubes (single and joined) was also inspected. The identification of the fire-induced damage mechanisms of the tubes was performed through optical microscopy, Scanning Electron Microscopy (SEM) and X-ray tomographic observations. Finally, the thermal analysis was carried-out on burnt specimens in order to better understand the multiphysical phenomenon taking place during the fire endurance tests. The experimental results have revealed that the combustion process of both single and joined tubes was described in four steps namely tube heating, resin degradation, ignition and flame decay. Moreover, it was found that no leakage was witnessed on the tubes (single and joined) outer surfaces during the fire endurance tests. The comparison between the pressure behaviour of the burnt single tube and the burnt joined one has proved that the single tube is much resistant under internal pressure loading than the burnt joined tube. Finally, the fire-induced damage included matrix cracking and delamination between the tube plies which was noticed from microscopic observations.

Experimental investigation of three-point bending behavior of assembled hybrid composite tubes before and after the fire endurance test

“…Figure 8(a) shows that the heat flow caused the phenomenon of delamination between the folds of the mechanical resistance layer as well as between the anti-corrosion layer (intact area) and the resistance mechanical layer (damaged area). These results are in agreement with the studies of Braiek et al 34 Chang et al 50 which showed that the delamination phenomenon is the result of the difference in thermal expansion between the damaged (hot) layer and the undamaged (cold) layer. This phenomenon is seen in Figure 8a’ and 8-a’‘.

Figure 8.Microscopic observations of the tube after the fire resistance test: (a) The formation of delamination, (b) The formation of carbonized residue, (c) Resin degradation.

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“…Concerning areas that do not have direct contact with fire, the most dominant damaged mode is matrix cracking (Figure 9) caused by the phenomenon of conduction of heat flow from the hot surface to the cold surface. 34

Figure 9.Matrix cracking.

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“…In another work, Gardinier et al 33 showed that delamination depth, as well as char thickness rise in proportion with the increase of the heat flux and the exposure time leading to post-fire flexural compressive and tensile properties reduction for composites materials with localized fire damage. Braiek et al 34 experimentally investigated the fire behavior of water-filled GFRP tubes under static pressure. To this end, fire endurance tests have been performed on single and adhesively bonded GFRP tubes.…”

“…However, the NFT welded tube withstood 1201500 and the DIN welded tube withstood only 100600 as is shown in Figure 5. To better quantify the fire resistance of single GFRP tubes, assembled by both DIN or NFT methods and adhesively bonded tubes, 34 a comparative review of the different holding durations are presented in Table 2. It can be concluded from this table that only the single tubes as well as the adhesively bonded tubes, were able to resist fire under a pressure of 3 bar for 30 min as recommended by the IMO.…”