Abstract: To investigate the effects of face sheet thickness on the impact resistance and residual compressive strength of composite foam sandwich panels, carbon fiber/PET foam specimens with face sheet thicknesses of 0.9 mm, 1.8 mm, and 2.7 mm were prepared. Drop-weight impact tests and subsequent compression after impact (CAI) tests were conducted at four impact energy levels: 5, 15, 25, and 35 J. The results indicated that face sheet thickness significantly influenced the impact response and damage modes, with thicker face sheets exhibiting superior impact resistance. Impact-induced damage reduced the residual compressive strength, and the magnitude of this reduction increased with higher impact energy. Specifically, as the impact energy increased from 5 J to 35 J, the compressive strength of the 2.7 mm specimens decreased from 28.25 MPa to 21.19 MPa. Furthermore, a model mapping the normalized residual compressive strength to impact energy was established. The critical damage threshold energies (E_th) for the three thicknesses were identified as 0.160 J, 1.433 J, and 2.465 J, respectively, indicating that increased face sheet thickness enhances structural damage tolerance. Finally, by introducing a thickness correction term K(t), a prediction model for normalized residual compressive strength incorporating thickness effects was proposed, yielding a good fit with the experimental data. This study provides a theoretical basis for the design optimization and safety assessment of composite foam sandwich structures under impact loading conditions.