بررسي رفتار استحكامي و سازوكار شكل گيري ترك در الياف شيشه‌ي نوع E تحت شرايط خوردگي

A STUDY ON THE STRENGTH BEHAVIOR AND CRACK FORMATION MECHANISM IN E-GLASS FIBER UNDER CORROSION CONDITIONS

در تحقيق حاضر رفتار استحكامي و سازوكار شكل‌‌گيري ترك در الياف شيشه‌ي E در محيط اسيد سولفوريك بررسي شده است. به‌منظور بررسي تغييرات خواص استحكامي الياف، نمونه‌هايي از نخ شيشه‌ي نوع E در محيط اسيد سولفوريك غوطه ور شده و كاهش استحكام و سفتي و همچنين كرنش شكست با افزايش زمان غوطه وري بررسي شده است. به‌منظور بررسي سازوكار خوردگي شيشه، آزمايش XRF بر روي نمونه‌هاي نخ شيشه‌ي سالم و خورده‌شده صورت گرفت. همچنين نمونه‌هاي فوق تحت آناليز SEM و آناليز عنصري EDX قرار گرفتند. نتايج افت استحكام و مدول كششي الياف شيشه برحسب زمان غوطه وري در اسيد و همچنين افت كرنش شكست الياف شيشه را نشان مي‌دهد. اين پديده به‌دليل خروج يون هاي آلومينيوم و كلسيم از ساختار شيشه است. با افزايش زمان غوطه‌وري در اسيد ترك‌هاي طولي و مارپيچ در سطح الياف شكل مي گيرد كه ناشي از تخليه‌ي يوني نخ شيشه است.

In this study, the strength behavior and crack formation mechanisms of E-glass fiber exposed to a sulfuric acid environment for different immersion times were investigated. In order to study strength degradation, E-glass fibers were immersed in sulfuric acid. The strength reduction, stiffness and fracture strain of fibers versus immersion times was studied. The corrosion mechanism of E-glass fiber exposed to acid was examined by a quantitative X-Ray Fluorescence (XRF) method. The results showed that the corrosion of E-glass fiber was accompanied by removal of Al, Ca and Fe ions from the fibers. Moreover, intact and degraded fibers were examined by Scanning Electron Microscope (SEM) and Energy Dispersive x-ray Microanalysis (EDX) methods to show the relation between the reaction of E-glass fiber elements and the acid environment. The ion-depletion-depth model was used to study the fracture process. The results showed that by increasing the immersion time in acid, the spiral stress, induced due to the shrinkage of the E-glass fiber surface, caused axial cracks in the fibers. Different points of the fibers in which cracks were generated were examined by the EDX method. The results were used to explain the role of Al, Ca and Fe ions in the creation of surface cracks on E-glass fibers subjected to sulfuric acid for different immersion times. By increasing the immersion time of the glass fiber in sulfuric acid, the magnitude of strength of the glass fiber was reduced. Strength degradation was caused by depletion of Al and Ca ions of the glass fiber. Moreover, this degradation depends on fiber fabrication, type and concentration of acid, and immersion time. After 192 h exposure time, based on the results of EDX, it could be seen that the depletion of Fe ions and their replacement with the hydrogen of acid caused micro-crack initiation on the glass fiber surface, where Fe ions were leached out. According to the ion-depletion-depth-model, by increasing immersion time, the crack formation mechanism was caused by the ion depletion of the E-glass fiber.