Crashworthiness and energy absorption of UHPFRC-steel composite sandwich structures under impact loading

This study aims to explore the dynamic crushing behaviors of a series of sandwich structures with varying configurations, which are composed of ultra-high performance fiber reinforced concrete (UHPFRC) face sheets and cores of steel and polyurethane (PU) foam. Drop-hammer impact tests were performed on 12 sandwich structure specimens, including four types (traditional frame (TF), ectopic frame (EF), corrugated plate (CP), and horizontal tube (HT)). The force profiles of EF type and HT type, compared with the other types, possessed low peak impact force (PIF) and high plateau force under the same impact energy. Test results indicated that the polyurea sprayed on the UHPFRC face did not affect the crashworthiness. Increases in core thickness can improve mean crushing force (MCF). The crashworthiness of the sandwich structure without the UHPFRC face sheet was weakened. The values of peak crushing force (PCF), MCF, energy absorption (EA), and specific energy absorption (SEA) under dynamic loading were greater than those in quasi-static loading. Finite element (FE) models were developed, validated, used to explore the energy absorption behavior in detail, and proved that EF-type and HTtype structures possess strong energy absorption stability. The multi-objective optimization showed that the HT-F structure is more suitable for practical applications.