Influence of acidic solutions on the strain distribution in glasspolyester composite pipes subjected to internal pressure

Abstract

The basic subject of this paper was the determination of the strain distribution in glass-polyester composite pipes subjected to internal pressure. Firstly, the test was performed on virgin pipe segments (without the influence of acidic solution) to determine the original properties of the examined composite pipes. Subsequently, the pipes were subjected to the influence of 25% acidic solution. Phosphoric and nitric acid were chosen, because of their frequent use in chemical industry, either as reactants or as products. The pipes were made by 'filament winding' method, with the angles of the glass fibers reinforcement [90°]2[±55°]4[90°]4. The tests were performed by subjecting the polymer composite pipes to internal pressure; the strain values were determined by strain gages in three directions: 0°, 90° and ± 45° with respect to the pipe axis. The tests were performed until the leakage occurred, up to the pressure value of approximately 100 bar, i.e. until the occurrence of the first cracks. Also, the micromechanical analysis on fracture surfaces was done by Scanning Electron Microscopy (SEM), which provided the knowledge about models and mechanisms of fracture due to the applied loading.

Cilj ovog rada je određivanje raspodele deformacija kod staklo-poliestar kompozitnih cevi koje su istaložene dejstvu unutrašnjeg pritiska. Prethodno su izvršena ispitivanja na netretiranim cevima u cilju određivanja originalnih svojstava. Zatim su cevi tretirane 25%-im rastvorom kiselina. Upotrebljene su fosforna i azotna kiselina zbog njihove česte upotrebe u hemijskoj industriji. Cevi su izrađene metodom namotavanja ('filament winding'), pri čemu su uglovi namotavanja staklenih vlakana [90 ]2[±55°]4[90°]4. Vrednosti deformacija usled delovanja unutrašnjeg pritiska su registrovane mernim trakama postavljenim u tri pravca: 0°, 90° i ± 45° u odnosu na osu cevi. Ispitivanja su izvođena do pojave procurivanja pri vrednosti pritiska od 100 bar, tj. do pojave prvih prslina. Prikazana je i mikromehanička analiza izvedena na prelomnim površinama pomoću skenirajućeg elektronskog mikroskopa (SEM) čime su dobijena saznanja o modelima i mehanizmima loma usled dejstva primenjenog opterećenja.