## 5 Conclusions  
The main contribution of this paper is to present a new core topology that can be applied as an inner core layer for metallic or composite sandwich structures. This study investigated the effectiveness of two different core sandwich structure topologies (folded and ribbon) for blast load attenuation.  
Figure 12: Facing sheets mid-span deflection and energy dissipation For RCSP components with variation in (**a**) core thickness, (**b**) the angle of corrugation and (**c**) core height.  
The dynamic behavior of the novel sandwich structure RCSP was investigated under air blast loading by employing a nonlinear explicit finite element simulation. The numerical model has been validated using the experimental field blast test for trapezoidal- and triangular-corrugated core sandwich panels. A good agreement was achieved by the numerical models for predicting the deformation/failure patterns for the field-tested panels with a maximum deviation of 11.93% for the back-plate defection. ANSYS/Autodyn was utilized to investigate the performance of the proposed structure under the same experimental test conditions. The blast performance of the investigated topologies was assessed in terms of the front-plate deflection, back-plate deflection, and energy dissipation. The results reveal that the ribbon core has a comparable blast resistance relative to the traditional corrugated core sandwich structures. The sandwich panel can suffer a larger impulse utilizing less amount of material compared with the traditional corrugated cores by about 64% for the TZRC and 56.9% for TRC. A parametric study was conducted to investigate the effect of design parameters on the blast performance of the novel core configuration, and the following was observed:  
* The back-plate deflection decreases with increasing front-plate thickness due to the increased stiffness. When using a front sheet with 2.6 mm thickness, the deflection decreases by an average 70% for the rear face sheet.
* The back-plate thickness has a negligible effect on the front-layer deflection however, the back-plate deflection decreases upon increasing the back-plate thickness.
* The sandwich panel with the thinner front-face plate could improve the energy-absorbing capabilities of the structure. However, under large blast loading, tearing damage may take place on the thinner front face.
* Increasing the core thickness has a negative impact on the blast behavior of the structure and also increasing the angle of corrugation more than 45\({}^{\circ}\) reduces the efficiency of the structure under the impact of blast loading.  
To conclude, the newly proposed ribbon core panels have shown superior blast performance than the traditional folded cores. The parametric study provides guidelines for designing the ribbon core sandwich structures according to the required protection level.  
Conceptualization, A.A.I. and M.A.; Methodology, A.A.I. and M.A.; Software, M.A.; Validation, M.A.; Formal Analysis, A.A.I. and M.A.; Investigation, A.A.I. and M.A.; Resources, A.A.I. and M.A.; Data Curation, A.A.I. and M.A.; Writing--Original Draft Preparation, A.A.I. and M.A.; Writing--Review and Editing, A.A.I. and M.A.; Supervision, A.A.I. All authors have read and agreed to the published version of the manuscript. This research received no external funding and the APC was provided by the University of Idaho Open Access Publishing Fund.  
No acknowledgment is needed.  
The authors declare no conflict of interest.