Study on energy absorption characteristics of EFFC-filled thin-walled metallic square tube rigid-flexible coupled body

To enhance the impact resistance of mine roadway support systems, this study designed an externally installed energy-absorbing device for unit-type hydraulic supports, consisting of foam-filled metal tubes. The device integrates Enriched Fiber Foamed Concrete (EFFC) into thin-walled square metal tubes, forming a lightweight rigid-flexible composite. Simulation and low-speed loading experiments were conducted to optimize energy absorption performance through three key parameters: EFFC material properties, thin-walled square tubes with induced defects, and EFFC-filled tube configurations. Compression tests on EFFC specimens revealed density-dependent deformation mechanisms, identifying 500 kg/m³ as the optimal filling density. Comparative experiments on five types of defect-induced EFFC-filled tubes demonstrated superior energy absorption and load characteristics relative to unfilled tubes. Key findings reveal a maximum load reduction of 29% in the composite compared to bare tubes, energy absorption capacity exceeding the sum of unfilled tubes and EFFC by up to 94.5%, and a 21% improvement in load fluctuation coefficient indicating reduced impact propensity. This cost-effective composite design provides a viable solution for anti-impact support equipment in coal mines, balancing high energy absorption with structural stability.