The design and multi-objective optimization of auxetic sandwich panels (ASPs) are performed to enhance the blastworthiness of armored fighting vehicles (AFVs). Various metastructures in the form of four auxetic geometries are proposed as the sandwich core: re-entrant honeycomb (REH), double-arrow honeycomb (DAH), star honeycomb (SH), and tetra-chiral honeycomb (CH). This paper employs a combination of finite element and machine learning methodologies to evaluate blastworthiness performance. Optimization is carried out using the nondominated sorting genetic algorithm II (NSGA-II) method. The optimization results show significant improvements in blastworthiness performance, with notable reductions in permanent displacement and enhancements in specific energy absorption (SEA). Global sensitivity analysis using SHapley Additive exPlanations (SHAP) reveals that cell thickness is the most critical factor affecting blastworthiness performance, followed by the number of cells and corner angle or radius for CH. The application of optimized ASP on AFVs shows promising results, with no failure occurring in the occupant floor. Furthermore, AFVs equipped with the optimized ASP DAH significantly reduce maximum displacement and acceleration by 39.00% and 43.56%, respectively, and enhance SEA by 48.30% compared to optimized aluminum foam sandwich panels. This study concludes that ASPs have potential applications in broader engineering fields.

A ballistic resistance of hard ceramic combined with aluminum foam sandwich (CAFS) constructions was investigated in this paper. This combination plate is constructed by a front faceplate (FFP), ceramic plates, an aluminum foam (Al-foam) panel, and a rear faceplate (RFP). The material used for the FFP and RFP was heat-treated mild steel with the thicknesses are 5 mm and 3.5 mm, respectively. The ceramic materials to be evaluated are B ₄ C, SiC, and Al ₂ O ₃ . Al-foams were fabricated by varying the stabilizer weight ratio of MgO and Al ₂ O ₃ . The Al-foams have a porosity of 79.93%–82.57%, a pore diameter of 2.51–2.82 mm, the relative density of 0.17–0.24, and plateau stress of 3.88–6.63 MPa. Ballistic tests were carried out only for aluminum foam sandwich (AFS) construction without ceramics to evaluate the manufacturing effect and to obtain a baseline ballistic plate to be improved. Ballistic tests are conducted by using 5.56 × 45 mm bullet with 50 m shooting range and bullet speed of 929–958 m/s. To validate the damage mode and energy absorption capability of the AFS, a numerical model is constructed. The numerical studies were conducted to investigate the damage mode and energy absorption capabilities of each part. The simulation has a good agreement with the experiment result on the damage mode. This model then to be used to study the effect of the additional hard ceramic layer. An interaction between hard ceramic and AFS is also investigated to get a new insight of the energy absorption mechanism during bullet penetration. A new finding shows that ceramic presses the Al-foam to solidify so that it can increase the energy absorbed by the Al-foam. The ceramic is impacted by a bullet pushing the Al-foam so that it undergoes solidification which leads to increasing absorbed energy.

Natural fibers contained in bamboo are beneficial to renewable, biodegradable, abundant availability, and cheap which could be a potential substitute of synthetic materials. Tensile strength of this material is important requirements in various structural application. In this research, fiber fabrication process optimization of three types of local bamboo namely Gombong (Gigantochloapseudoarundinacea), HaurHejo (Bambusatuldoides), and Tali (Gigantochloa apus) was investigated. These fibers were processed by creating a variety of the NaOH concentrations of 4 % and 6 %, immersion times of 1, 2, and 3 hours, and immersion temperatures of 25 °C and 60 °C. The process parameters and its level variations of bamboo fiber fabrication were optimized using Taguchi method. Then the contribution of each process parameter was observed using the analysis of variance (ANOVA). From Taguchi method, the optimal parameter for highest tensile strength was obtained from Tali bamboo, indicated by 4 % NaOH, 2 hours immersion time, and 60 °C immersion temperature. Meanwhile, the ANOVA revealed that the contributions for each parameter are 70 % for bamboo type, 7 % for NaOH concentration, 4 % for immersion time, and 17 % for immersion temperature with error contribution of 2 %. By using these data, it could be concluded that bamboo type selection is a critical parameter to obtain bamboo with high tensile strength. While NaOH concentration, immersion time, and immersion temperature are not critical parameters which gave flexibility in the selection process. FTIR analysis was carried in order to observe chemical bonding in bamboos. The results of FTIR on the bamboo fibers were indicated Tali bamboo has larger lignin levels decreasing than HaurHejo and Gombong, this indicates in higher tensile strength for Tali bamboo fiber.

Design and multi-objective optimization of auxetic sandwich panels (ASPs) are performed to enhance the blastworthiness of armored fighting vehicles (AFVs). Various metastructures in the form of four auxetic geometries are proposed as the sandwich core: re-entrant honeycomb (REH), double-arrow honeycomb (DAH), star honeycomb (SH), and tetra-chiral honeycomb (CH). This paper employs a combination of finite element (FE) and machine learning (ML) methodologies to evaluate blastworthiness performance. Optimization is carried out using the non-dominated sorting genetic algorithm II (NSGA-II) method. The optimization results show significant improvements in blastworthiness performance, with notable reductions in permanent displacement and enhancements in specific energy absorption (SEA). Global sensitivity analysis (GSA) using SHapley Additive exPlanations (SHAP) reveals that cell thickness is the most critical factor affecting blastworthiness performance, followed by the number of cells and corner angle or radius for CH. The application of optimized ASP on AFVs shows promising results, with no failure occurring in the occupant floor. Furthermore, AFVs equipped with the optimized ASP DAH significantly reduce maximum displacement and acceleration by 39.00% and 43.56%, respectively, and enhance SEA by 48.30% compared to optimized aluminum foam sandwich panels (AFSPs). This study concludes that ASPs have potential applications in broader engineering fields.