Dynamic behaviour of composites reinforced with needles from fir trees Alexandru Ioan Rădoi, Cosmin Mihai Miriţoiu, Mihaela Bogdan, Marius Marinel Stănescu, Dumitru Bolcu and Ionuţ Geonea MATEC Web Conf., 343 (2021) 01001 Published online: 04 August 2021 DOI: 10.1051/matecconf/202134301001