Low-Velocity Impact Behavior of 3D-Printed Sandwich Panels with Integrated Composite Face Sheets

Composite panels are made of a core and skins that are typically bonded with adhesive. Traditional adhesive bonding is time-consuming and requires precision, often leading to debonding under varied loading conditions. Additionally, thermal expansion differences between the core, skin, and adhesive cause residual stresses, compromising performance. This research develops a cost-effective method for creating integrated sandwich panels, addressing the effectiveness of such unification under low-velocity impact loading. Using a standard dual-nozzle fused deposition modeling 3D printer with minimal modifications, continuous fibers embedded in a thermoplastic polymer for the skin and a thermoplastic polymer for the core are simultaneously deposited, ensuring material consistency between the core and matrix of the skins, leading to an integrated panel. Integrated samples are compared to pure (fiberless) and adhesive-bonded samples under an 18 J low-velocity impact test. The integrated samples show significant improvements, with maximum impactor acceleration (279.7 m s⁻²) and force per unit mass (83 283 N kg⁻¹), surpassing adhesive-bonded and pure samples by 35 and 110%, respectively. Additionally, integrated samples show significantly less damage, with dent diameters (9.77 mm) and dent depths (1.52 mm) considerably lower. These findings highlight the benefits of this approach in enhancing impact resistance, reducing damage, and improving energy absorption in composite sandwich structures.