Abstract
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.
Highlights
Since their discovery in 1940s, polymeric composites were continuously studied and integrated in multiple applications, including aerospace [1, 2], automotive industry [3,4,5] and wind turbines [6, 7]
Many studies were conducted regarding the properties of glass fibre reinforced polymeric composites and their usage [11, 12], for example Spanu et al [13] conducted a study regarding the compressive properties of GFRP, they obtained many results for the same material as it was characterized by a high degree of inhomogeneity
For the present study two types of epoxy glass fibre reinforced composites (GFRP) were manufactured using the same twill 2x2 E-glass fibre (280 g/m2) and two epoxy systems composed of Resoltech 1050 epoxy resin and Resoltech 1058 hardener, one system was used during its shelf-life and one was used out of its shelf-life
Summary
Since their discovery in 1940s, polymeric composites were continuously studied and integrated in multiple applications, including aerospace [1, 2], automotive industry [3,4,5] and wind turbines [6, 7]. Carbon fibre reinforced polymeric composites (CFRP) are the most used composite materials for advanced applications where high loads are implied, while in applications where lower loads or low signal attenuating properties are implied, the glass fibre reinforced polymeric composites (GFRP) are preferred [8]. Stefanescu et al [16] studied the low velocity impact properties of different hybrid fibre reinforced composite laminates and it was concluded that the best performances were obtained for laminates that have glass fibre external layers. Beside these studies, many researches were conducted in the last decade regarding hybrid fibre reinforced polymeric composites [7, 17, 18], 3D printed fibre reinforced composites [19,20,21], and even self-healing fibre reinforced polymeric composites [22, 23]
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