Comparison between basalt fiber and glass fiber reinforced vinylester composites: post impact behaviour

Due to the ever-increasing application of polymer composites in several industrial fields and the environmental requirements for reinforcements in polymer matrices, the reinforcement potential of newer fibres is currently investigated. During the last decade, the possible use of basalt fibres as reinforcing material for polymers has been studied extensively. Basalt fibres are produced by melt-spinning from naturally existing basalt rocks which are volcanic and effusive rocks saturated with 45-52 wt% SiO2. Due to its origin, basalt fibre shows excellent properties: high Young’s modulus, excellent heat resistance, good insulation properties (acoustic and thermal) and good damping characteristics. Impact resistance of composite materials is an important area of research. Fibre reinforced polymer composites (FRP) typically show poor resistance to impact events. Moreover, uncertainties about the dominant mechanisms of damage make it difficult to assess the effect of impact on the performance and residual strength of FRPs. This situation is compounded by the fact that often the damage produced is not visible. It is therefore essential to understand the impact behaviour of composites to properly design and use them. The primary focus of this research has been aimed at investigating the response to low velocity impact of two different laminates, namely a glass and a basalt woven fabric reinforced vinylester composites. The specimens were manufactured by Resin Transfer Moulding (RTM), using 14 layers of glass and basalt fibres and keeping constant the laminate thickness (3 mm). Plain woven glass and basalt fabrics were used as reinforcement with the same fibre areal weight (220 g/m2) for comparison purposes. An epoxy based vinylester resin was used as matrix material. All laminates were impacted at various levels of energy (from 5 to 15 Joules) using an hemispherical drop weight striker and then subjected to post impact three-point bending tests. Moreover, non-impacted specimens were tested in flexure for comparison purposes. The trend of flexural properties (strength and modulus) as a function of impact energy along with scanning electron microscopy observations allowed us to assess the difference in performance between the two types of laminates.