Estudo do comportamento de diferentes materiais de cobertura frente à chuva de granizo, a partir do impacto de uma esfera de aço

Abstract

Recent climate changes have increased the incidence of rain and hail storms, which can damage homes, buildings, factories, plantations, automobiles, among others. Thus, the study of roofing materials has become extremely necessary in regard of resistance to impact by hail. The simulation of hail is complex because of its specific morphology, therefore many simulation studies have been made using steel balls and ice balls. In Brazil, the standard ABNT NBR 15575-5 - Annex C describes a test method to verify the roofing material's resistance to hail damage, stones and others by using steel balls. In this work the occurrence of damage in different types of roofing materials in relation to the free drop of a steel ball with an inch diameter was analysed according to the standard. In addition, the coefficient of restitution for the materials was measured to correlate the result with the ability of the material to resist the impact. The coefficient of restitution is measured according to adaptations of the standard NBR 13818 - Annex Q. The coefficient of restitution values were related to the amount of absorbed and/or returned energy by the material and with the susceptibility to damage from a dropping rigid body. Ceramic tiles were performed on a three-point bending test. The results showed that the impact of solid particles, such as hail, can cause cosmetic effects on covering materials depending on the incident energy. Furthermore, the impact of solid particles gives rise to fissures or similar defects in ceramic and fiber cement tiles, and may lead the tiles to a functional failure (loss of tightness). Considering the ceramic tiles, the results of the mechanical test suggest reduction of mechanical strength. However, this verification of any reduction in the mechanical strength of the ceramic tiles requires further experimental evidence.