The main aim of this article is the analysis of the deformation process of regular cell structures under quasi-static load conditions. The methodology used in the presented investigations included a manufacturability study, strength tests of the base material as well as experimental and numerical compression tests of developed regular cellular structures. A regular honeycomb and four variants with gradually changing topologies of different relative density values have been successfully designed and produced in the TPU-Polyflex flexible thermoplastic polyurethane material using the Fused Filament Fabrication (FFF) 3D printing technique. Based on the results of performed technological studies, the most productive and accurate 3D printing parameters for the thermoplastic polyurethane filament were defined. It has been found that the 3D printed Polyflex material is characterised by a very high flexibility (elongation up to 380%) and a non-linear stress-strain relationship. A detailed analysis of the compression process of the structure specimens revealed that buckling and bending were the main mechanisms responsible for the deformation of developed structures. The Finite Element (FE) method and Ls Dyna software were used to conduct computer simulations reflecting the mechanical response of the structural specimens subjected to a quasi-static compression load. The hyperelastic properties of the TPU material were described with the Simplified Rubber Material (SRM) constitutive model. The proposed FE models, as well as assumed initial boundary conditions, were successfully validated. The results obtained from computer simulations agreed well with the data from the experimental compression tests. A linear relationship was found between the relative density and the maximum strain energy value.

The mechanical behavior of titanium alloys has been mostly studied in quasi-static conditions when the strain rate does not exceed 10 s⁻¹, while the studies performed in dynamic settings specifically for Ti-based composites are limited. Such data are critical to prevent the “strength margin” approach, which is used to assure the part performance under dynamic conditions in the absence of relevant data. The purpose of this study was to obtain data on the mechanical behavior of Ti-based composites under dynamic condition. The Metal Matrix Composites (MMC) on the base of the alloy Ti-6Al-4V (wt.%) were made using Blended Elemental Powder Metallurgy with different amounts of reinforcing particles: 5, 10, and 20% of TiC or 5, 10% (vol.) of TiB. Composites were studied at high strain rate compression ~1–3 × 10³·s⁻¹ using the split Hopkinson pressure bar. Mechanical behavior was analyzed considering strain rate, phase composition, microstructure, and strain energy (SE). It is shown that for the strain rates up to 1920 s⁻¹, the strength and SE of MMC with 5% TiC are substantially higher compared to particles free alloy. The particles TiC localize the plastic deformation at the micro level, and fracturing occurs mainly by crushing particles and their aggregates. TiB MMCs have a finer grain structure and different mechanical behavior. MMC with 5 and 10% TiB do not break down at strain rates up to almost 3000 s⁻¹; and 10% MMC surpasses other materials in the SE at strain rates exceeding 2200 s⁻¹. The deformation mechanism of MMCs was evaluated.

The goal of the present work is a systematic study on an influence of a strain rate on the mechanical response and microstructure evolution of the selected titanium-based materials, i.e., commercial pure titanium, Ti-6Al-4V alloy with lamellar and globular microstructures produced via a conventional cast and wrought technology, as well as Ti-6Al-4V fabricated using blended elemental powder metallurgy (BEPM). The quasi-static and high-strain-rate compression tests using the split Hopkinson pressure bar (SHPB) technique were performed and microstructures of the specimens were characterized before and after compression testing. The strain rate effect was analyzed from the viewpoint of its influence on the stress–strain response, including the strain energy, and a microstructure of the samples after compressive loading. It was found out that the Ti-6Al-4V with a globular microstructure is characterized by high strength and high plasticity (ensuring the highest strain energy) in comparison to alloy with a lamellar microstructure, whereas Ti6-Al-4V obtained with BEPM reveals the highest plastic flow stress with good plasticity at the same time. The microstructure observations reveal that a principal difference in high-strain-rate behavior of the tested materials could be explained by the nature of the boundaries between the structural components through which plastic deformation is transmitted: α/α boundaries prevail in the globular microstructure, while α/β boundaries prevail in the lamellar microstructure. The Ti-6Al-4V alloy obtained with BEPM due to a finer microstructure has a significantly better balance of strength and plasticity as compared with conventional Ti-6Al-4V alloy with a similar type of the lamellar microstructure.

An experimental and numerical study on three flat specimen geometries for characterization of the dynamic shear behavior of metals with the use of the compression Split Hopkinson Pressure Bar (SHPB) technique is presented in the paper. The aim of the work is to determine for which specimen shape the most equilibrium state of stress is achieved, and the stress state in the shear zone is closest to simple shear during dynamic deformation. The high strain rate tests were performed on a Ti-6Al-4V titanium alloy, which was deformed with shear strain rate from 9200 to 12,700 s⁻¹. The obtained results indicate that the specimen geometry marked as D2S (double-shear version 2 specimen) with double shear zones guarantees high quality of the obtained experimental data.

This paper presents experimental and numerical results of the mechanical response of body-centered cubic (BCC) lattice structures manufactured with the fused filament fabrication (FFF) method using polyethylene terephthalate glycol (PETG) material. The BCC structures were subjected to uniaxial compression tests using a universal strength machine with three different values of deformation velocities. Moreover, dog-bone specimens were manufactured in three orientations to identify the PETG mechanical properties, which were supplemented with the literature data of PETG tested under compression. Then, the mechanical properties were correlated in the LS-Dyna code using a visco-plastic material model, which was used to numerically reproduce the experimental uniaxial tensile test conditions. The compression tests of BCC were simulated, and the results of experiments and numerical simulations were compared with satisfactory agreement. It was demonstrated that the properties of the 3D printed PETG varied, depending on both the printing direction and the type of applied load condition (compression/tension). Furthermore, the results also show that for the strut-based lattice structures manufactured with the FFF method and PETG material, it is mandatory to consider the above remark while simulating this type of mechanical behavior in a structure. Additionally, the influence of element type and cross section of the struts was also analyzed in this work. Results presented in the paper confirmed that the BCC lattice structures were effective in terms of energy absorption capacity, and they demonstrated long-range plateau deformation force plots.