1. Introduction In recent years, natural fibres, either extracted from plants, such as jute, flax, hemp, or of mineral origin, such as basalt, are increasingly proposed as a non- toxic and more easily recyclable alternative to glass fibres as a result of stricter environmental require- ments. More specifically, the higher density of basalt fibres (about 2700 kg/m 3 ) is widely compen- sated by their higher modulus, excellent heat resist- ance, good resistance to chemical attack and to wear and low water absorption [1]. This suggests not only the possibility to apply them as a replacement for glass fibres, which has been the object of a pre- vious study [2], but also the idea of making hybrids, able to combine, possibly with a positive global effect, the properties of both materials. As a matter of fact, hybridisation of basalt fibres has been attempted with ceramic fibres, to provide improved hot wear resistance to friction materials [3], and with high tensile strength fibres, such as carbon [4] and Kevlar [5]. In these cases, basalt provides a suf- ficient resistance, in particular to impact, even supe- rior to that obtained by a possible substitution with glass fibres, coupled in particular with a substantial reduction in costs, with respect to carbon and Kevlar fibres. In the case of basalt/Nylon fibres hybrid lam- inates, low tensile modulus of Nylon is improved by adding basalt fibres, whilst nylon provides some more impact resistance [6]. In contrast, basalt hybridisation with glass fibres would imply using two fibres, which are chemically not very different: continuous basalt fibre has a not very different content in silica and alumina from glass fibres and also a comparable, if not superior, tensile strength [7]. A significant difference is their behaviour under corrosion: for basalt fibres, resist- ance to acids is much higher than that to alkalis, whilst for glass fibres resistance to acids is nearly 449 Post-impact mechanical characterisation of E-glass/basalt woven fabric interply hybrid laminates I. M. De Rosa, F. Marra, G. Pulci, C. Santulli * , F. Sarasini, J. Tirillò, M. Valente Sapienza – Università di Roma, Department of Chemical Engineering Materials Environment, Via Eudossiana 18 - 00184 Rome, Italy Received 22 September 2010; accepted in revised form 4 December 2010 Abstract. Post-impact properties of different configurations (symmetrical and non-symmetrical) of hybrid laminates including E-glass and basalt fibre composites, all with volume fraction of fibres equal to 0.38±0.02 and manufactured by RTM, have been studied. With this aim, interlaminar shear strength tests and four-point flexural tests of laminates impacted with different energies (0, 7.5, 15 and 22.5 J) have been performed. Acoustic emission (AE) localisation and AE evolution with applied flexural stress was studied to support impact damage characterisation, provided by SEM and transient ther- mography. The results indicate that a symmetrical configuration including E-glass fibre laminate as a core for basalt fibre laminate skins presents the most favourable degradation pattern, whilst intercalation of layers may bring to further improvement of the laminate properties, but also to more extended and complex damage patterns. Keywords: polymer composites, mechanical properties, basalt fibres, acoustic emission, post-impact degradation eXPRESS Polymer Letters Vol.5, No.5 (2011) 449–459 Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2011.43 * Corresponding author, e-mail: carlo.santulli@uniroma1.it © BME-PT