Experimental and numerical investigations of hybrid-fibre engineered cementitious composite panels under contact explosions

In this study, the blast response of hybrid-fibre engineered cementitious composite (HFECC) panels with 1.75% polyvinyl alcohol and 0.58% steel fibres (by volume) is experimentally and numerically evaluated for the first time. For blast testing, HFECC and normal reinforced concrete (NRC) panels were tested under contact explosions generated by Plastic Explosive 4 (PE4) on a demolition range. The crater diameter, spalling diameter and fragment size were measured and compared. The averaged crater and spalling diameters of the NRC panels were 173.55 mm and 272.87 mm, respectively, while those of the HFECC panels were 91.16 mm and 178.93 mm, respectively. The fragment size of the HFECC panels was larger than 19 mm, whereas the fragments of the NRC panels had a wide size distribution ranging from < 1.7 mm to > 19 mm. An effective finite element model is also developed to reproduce the responses of the HFECC and NRC panels under blast loads. In the numerical model, a dynamic increase factor formula newly developed by the authors is incorporated to describe the rate sensitivity of HFECC in tension. A particle-based approach is employed, for the first time, to explicitly model the blast load applied on the concrete panels. The efficiency and accuracy of the numerical model are validated by comparing the numerical prediction with the experimental data. The validated model is then used to explore the blast resistance of a reinforced HFECC panel. It is found that the crater and spalling diameters obtained for the reinforced HFECC panel are decreased by 53.6% and 41.1% compared with those of the NRC panel. The damage distribution in the reinforced HFECC panel becomes less localised with the increase of the ductility of HFECC. The numerical results also show that the blast resistance of the distal surface relies more on the ductility of the matrix than that of the proximal surface.