In this manuscript, the energy absorption behavior of the empty aluminum and ALPORAS foam-filled square tubes is investigated through experimental and numerical routes. The experimental method is conducted by an axial impact test apparatus. To discover more details about crushing behavior, LS DYNA software is used for numerical simulation of the tests. The results of both methods are in satisfactory compliance. As a novelty, the crash performance of tubes filled with different foam densities is investigated. To examine the foam density effect on energy absorption of the tube, multi-layer foams with three different densities have been applied. It has been proven that filling the tubes with gradient foam improves the crash characteristics of the tubes. Numerical results revealed that tubes filled with gradient foam filler can absorb more energy than empty and tubes filled with different individual foams of lower weight. In numerical simulations, the required foam parameters are estimated from existing formulas. Compression test results of foam with different densities are implemented for calibrating these formulas.