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This paper aims to investigate experimentally and using finite element analysis the performance of using three-dimensional printing technology to produce a composite sandwich panel that is made of the high-flexible core as well as with high stiffness upper and lower surfaces made of a glass fiber reinforced composite filament. There are many advantages of using sandwich structures in many applications, especially the aerospace field, where the high stiffness to strength and the lightweight is the most preferred in such applications. The conventional manufacturing methods that are used to produce sandwich panels are limited to particular core geometry, whereas manufacturing a composite core is not possible by these traditional production methods. So by using additive manufacturing technology, it becomes more applicable to design a combination of different geometries and materials to achieve properties that have never been made before, especially combining flexibility and high energy absorption keeping high strength to failure. A central deflection to a length of 0.26 is observed within the elastic zone, a remarkable ratio in beams that reflects the three-dimensional printed sandwich beams’ capability with a highly flexible core to absorb energy that would open doors for many industrial applications that is attributed to the lowest flexural rigidity (167E-3Pa · m4) of the sandwich by using the TriHex infill pattern. In contrast, the Gyroid infill structure could afford the highest central load (0.264 kN). At the peak load applied on the sandwich beam, a maximum error of 5.4% is estimated by finite element analysis lower than the experimental values.

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It is necessary to improve the machinability of difficult-to-cut materials such as hardened steel, nickel-based alloys, and titanium alloys as these materials offer superior properties such as chemical stability, corrosion resistance, and high strength to weight ratio, making them indispensable for many applications. Machining with self-propelled rotary tools (SPRT) is considered one of the promising techniques used to provide proper tool life even under dry conditions. In this work, an attempt has been performed to analyze, model, and optimize the machining process of AISI 4140 hardened steel using self-propelled rotary tools. Experimental analysis has been offered to (a) compare the fixed and rotary tools performance and (b) study the effect of the inclination angle on the surface quality and tool wear. Moreover, the current study implemented some artificial intelligence-based approaches (i.e., genetic programming and NSGA-II) to model and optimize the machining process of AISI 4140 hardened steel with self-propelled rotary tools. The feed rate, cutting velocity, and inclination angle were the selected design variables, while the tool wear, surface roughness, and material removal rate (MRR) were the studied outputs. The optimal surface roughness was obtained at a cutting speed of 240 m/min, an inclination angle of 20°, and a feed rate of 0.1 mm/rev. In addition, the minimum flank tool wear was observed at a cutting speed of 70 m/min, an inclination angle of 10°, and a feed rate of 0.15 mm/rev. Moreover, different weights have been assigned for the three studied outputs to offer different optimized solutions based on the designer’s interest (equal-weighted, finishing, and productivity scenarios). It should be stated that the findings of the current work offer valuable recommendations to select the optimized cutting conditions when machining hardened steel AISI 4140 within the selected ranges.