The present paper was focused on studying the influence of shelf life of an epoxy matrix on the mechanical properties of glass fibre reinforced composites. For the study, two types of the same epoxy system were used, one during its shelf life and one out of its shelf life. The reinforcement used consisted in E-glass fibre fabric. Mechanical investigations were realized in order to compare the materials in terms of loss of mechanical strength and elastic properties. Therefore, three mechanical tests were performed: tensile tests, in-plane shear and open-hole tensile tests. The results showed that the shelf life affects the mechanical properties of the polymeric composite. A decrease of 24% in tensile strength was recorded along with a 28% decrease of the in-plane shear strength and 55% of open-hole tensile strength for the composite manufactured with the out of shelf life epoxy system compared with the other composite. An overall reduction of mechanical strength and elastic properties of the composite material was observed, primarily due to polymeric matrix degradation, which after long periods it could be prone to brittleness and susceptible to delamination and fracture. The thermogravimetric analysis showed that thermal induced changes are happening at a higher speed in the out of shelf life composite, a lower mass loss being registered for new epoxy composite.
Experimental investigation of mechanical properties of glass fibre reinforced composites in different environment