Bio-based composites with passive control layers were investigated by means of a comprehensive set of experiments. The structure, composed of an exterior layer of PLA/Flax and an inserted rubber layer, were manufactured using 3D printing technology. Tensile tests on PLA/Flax and rubber specimens revealed that it exhibited higher stiffness, whereas rubber demonstrated superior elongation. Additionally, three-point bending tests were conducted on 3D-printed composites with varying viscoelastic layer thicknesses (VL) to assess their bending performance. However, the composite with a single 1-mm thick viscoelastic layer (V 1 t 1 ) showed optimal deflection and stiffness compared to counterparts with different viscoelastic layers. Furthermore, resonance vibration experiments were performed to investigate dynamic parameters such as frequencies and modal loss factors. Based on the experiments, it was determined that V 1 t 1 was the composite that offered the optimal compromise between mechanical and vibration behavior due to its excellent damping characteristics.