A challenge for developing acoustic metamaterials (AMMs) is considering the application of broadband muffling and load bearing capacity simultaneously. In this paper, a honeycomb based graded AMM muffler is proposed, which can widen the attenuation band and improve the structural stiffness without any external device by means of integrated design. Firstly, the acoustic and mechanical characteristics of the muffler unit cell are theoretically and numerically studied, and the graded muffler is designed based on these characteristics. The numerical results show that the graded muffler widens the attenuation bandwidth of the unit cell, and the simulation also shows that the graded muffler has greater stiffness than the uniform one. The stiffness driven muffler provides new possibilities for the design of advanced metamaterial with simultaneous sound insulation and load bearing performances.

Investment casting combined with the additive manufacturing technology enables production of the thin-walled elements, that are geometrically complex, precise and can be easy commercialized. This paper presents design of aluminium alloy honeycombs, which are characterized with light structure, internal parallel oriented channels and suitable stiffness. Based on 3D printed pattern the mould was prepared from standard ceramic material subjected subsequently to appropriate heat treatment. Into created mould cavity with intricate and susceptible structure molten AC 44200 aluminium alloy was poured under low pressure. Properly designed gating system and selected process parameters enabled to limit the shrinkage voids, porosities and misruns. Compression examination performed in two directions showed different mechanisms of cell deformation. Characteristic plateau region of stress-strain curves allowed to determine absorbed energy per unit volume, which was 485 or 402 J/mm3 depending on load direction. Elaborated technology will be applied for the production of honeycomb based elements designated for energy absorption capability.

In this paper were conducted virtual tests to assess the impact of geometry changes on the response of metallic hexagonal honeycomb structures to applied loadings. The lateral compressive stress state was taken into consideration. The material properties used to build numerical models were assessed in laboratory tests of aluminium alloy 7075. The modelling at meso-scale level allow to comprehensive study of honeycomb internal structure. The changes of honeycomb geometry elements such as: fillets radius of the cell edges in the vicinity of hexagonal vertexes, wall thickness were considered. The computations were conducted by using finite element method with application of the ABAQUS finite element method environment. Elaborated numerical models allowed to demonstrate sensitivity of honeycomb structures damage process response to geometry element changes. They are a proper tools to perform optimization of the honeycomb structures. They will be also helpful in designing process of modern constructions build up of the considered composite constituents in various branches of industry. Moreover, the obtained results can be used as a guide for engineers. Conducted virtual tests lead to conclusion that simplification of the models of internal honeycomb structure which have become commonplace among both engineers and scientist can lead to inaccurate results.

This paper is focused on investigating the mechanisms associated with different failure modes of copper (C101) sandwich panels with honeycomb cores of different heights subjected to flexural loading. Honeycomb core is made up of copper strips which were formed to required shapes using Dies fabricated by Electric Discharge Wire cut machining technique. All the joints in the sandwich panel were established through Brazing technique. Three-point bending test was conducted as per ASTM standard C-393. It was observed that increase in height of the core resulted in panels with higher strength to weight ratio. It also exhibited higher stiffness to weight ratio and very high strain energy absorption ability. An increase in flexural strength was reported with a maximum of 43% improvement for 10.9 mm core compared to 6.9 mm core. Further, 81.75% increase in absorbed strain energy was reported for 10.9 mm thick panel compared to 6.9 mm. The Optical and scanning electron microscope (SEM) analysis confirmed the establishment of good bonding between the filler and the substrate. Energy-dispersive Spectroscopic (EDS) analysis revealed the presence of Cu, Al, Zn, SiO2 and CaCO3 in the substrate. Further it also revealed the presence of Cu, CaCO3 and GaP in the filler material. The failure mode map was constructed which can be used for predicting different types of failures more likely to occur for specific parameters of copper sandwich panel. The dominant failures occurred during testing was in good agreement with the prediction done through failure mode map. The appreciable results in the proposed research may be supportive in construction of cooling system. The structure development and process control are convenient in mass production in automobile industries.