The following study investigates the dynamic response and mechanical elastic properties of four different composite materials: flax fiber with epoxy resin, carbon fiber with epoxy resin, and two types of glass fiber composites — one with an inorganic resin and the other with a 30% organic resin component. The primary objective is to characterize the elastic moduli and damping coefficients of these composites at varying temperatures. Utilizing the impulse excitation method, the natural frequencies of the composites were measured and analyzed according to the ASTM E1876-21 standard to evaluate the longitudinal modulus E1 and the shear modulus G12. To enhance the accuracy of these evaluations, the coefficients of thermal expansion (CTEs) in three directions were also evaluated by directly measuring strains of each composite during a typical thermal expansion.