Material jetting (MJ) technology is an additive manufacturing method that selectively cures liquid photopolymer to build functional parts. The use of MJ technology has increased in popularity and been adapted by different industries, ranging from biomedicine and dentistry to manufacturing and aviation, thanks to its advantages in printing parts with high dimensional accuracy and low surface roughness. To better understand the MJ technology, it is essential to address the capabilities, applications and the usage areas of MJ. Additionally, the comparison of MJ with alternative methods and its limitations need to be explained. Moreover, the parameters influencing the dimensional accuracy and mechanical properties of MJ printed parts should be stated. This paper aims to review these critical aspects of MJ manufacturing altogether to provide an overall insight into the state of the art of MJ.

In the present study, a comparative compression investigation of anti-tetrachiral and modified re-entrant lattices was conducted in-plane direction using experimental and numerical analyses. Lattice structures were manufactured using fused deposition modelling 3D printing technology and crushed at quasi-static condition. Nonlinear finite element (FE) models of both structures were established, and the FE results were systematically compared with the experimental results. The onset of densification phases of both structures was determined numerically. Results indicate that deformation modes strongly affect the force-deflection response of both designs. In this manner, failure locations and buckling deformation in the tests were identified to find a relation with theory and to modify geometries. The anti-tetrachiral design exhibits higher specific energy absorption than modified re-entrant hexagonal lattices. Beyond the auxetic characteristics, deformation mechanism of the anti-tetrachiral lattices provides an opportunity to construct excellent crush absorption in-plane direction thanks to its high shear strength stem from its unique deformation mechanism.

Crash box structures are used for mitigating the transfer of impact sourced loads to the vehicle cabinet to prevent injuries and casualties. They are designed in the shape of tubes, and during loading, they can be depleted as sacrificial structures. For increasing energy absorption capability, particular types of fillers can be used in crash boxes. In the present study, the outcome of two particular filling structures on the energy absorption capability of crash boxes is investigated experimentally and numerically. As filling materials, PolyJet printed polymer re-entrant and anti-tetrachiral structures are utilized to investigate the effect of two main auxetic mechanisms of re-entrant and chiral. The crash boxes made of empty, re-entrant and anti-tetrachiral filled AA6063 square tubes are crushed experimentally under quasi-static conditions and numerical models are validated. Specific energy absorption (SEA) and crush force efficiency (CFE) are obtained for comparison to select the best configuration. The comparison of the SEA value of the anti-tetrachiral and re-entrant lattices filled tubes over the empty tube shows 28.5% and 20.6% improvements, respectively, while a similar trend in CFE with improvements of 50.6% and 40.27% for lattices are experienced, in the same sequence.

In this study, the cyclic compression and crush behavior of chiral auxetic lattice structures produced from titanium alloy (Ti6Al4V) metallic powder using electron beam melting (EBM) additive manufacturing technology is investigated numerically and experimentally. For material characterization and understanding the material behavior of EBM printed parts, tensile and three-point flexural tests were conducted. Log signals produced during the EBM process were investigated to confirm the stability of process and the health of the produced parts. Furthermore, a compressive cyclic load profile was applied to the EBM printed chiral units having two different thicknesses to track their Poisson’s ratios and displacement limits under large displacements in the absence of degradation, permanent deformations and failures. Chiral units were also crushed to investigate the effect of failure and deformation mechanisms on the energy absorption characteristics. Moreover, a surface roughness study was conducted due to high surface roughness of EBM printed parts, and an equation is offered to define load-carrying effective areas to prevent misleading cross-section measurements. In compliance with the equation and tensile test results, a constitutive equation was formed and used after a selection and calibration process to verify the numerical model for optimum topology design and mechanical performance forecasting using a non-linear computational model with failure analysis. As a result, the cyclic compression and crush numerical analyses of EBM printed Ti6Al4V chiral cells were validated with the experimental results. It was shown that the constitutive equation of EBM printed as-built parts was extracted accurately considering the build orientation and surface roughness profile. Besides, the cyclic compressive and crush behavior of chiral units were investigated. The regions of the chiral units prone to prematurely fail under crush loads were determined, and deformation modes were investigated to increase the energy absorption abilities.

This study aimed to determine the effects of design parameters, including the liquid/solid ratio (L/S), Na₂SiO₃/NaOH weight ratio, and curing temperature, on class F fly ash-based geopolymer composites. For this purpose, two disparate sources of fly ash were supplied from Çatalağzı (FA) and İsken Sugözü (FB) Thermal Power Plants in Turkey. Two different L/S ratios of 0.2 and 0.4 were used. The Na₂SiO₃/NaOH ratios in the alkaline solutions were 1, 1.5, 2, 2.5, and 3 by weight for each type of geopolymer mixture. Then, 40 different mixes were cured at two specific temperatures (70 °C and 100 °C) for 24 h and then preserved at room temperature until testing. Thereafter, the physical water absorption properties, apparent porosity, and bulk density were examined at 28 days on the hardened mortars. Additionally, compressive and flexural tests were applied to the geopolymers at 7, 28, and 90 days. It was found that the highest compressive strength was 60.1 MPa for the geopolymer manufactured with an L/S of 0.2 and Na₂SiO₃/NaOH ratio of 2. Moreover, the best thermal curing temperature for obtaining optimal strength characteristics was 100 °C for the FB.

Our research investigated the energy absorption characteristics of chiral auxetic lattices filled cylindrical composite tubes subjected to a uniaxial and lateral quasi-static load. The lattice structures were manufactured using a 3D printing technique. Carbon fiber composite tubes without filler material were initially subjected to uniaxial and lateral quasi-static crushing load. The same types of experiment were then performed on chiral lattices and chiral lattices filled composite tubes. For the different cases, the load–displacements curves were analyzed and the specific energy absorption (SEA) values were compared. The SEA capability for the axial quasi-static crushing of the chiral lattices filled composite tubes decreased in comparison with the hollow composite design. However, the most significant result was that the average SEA value in the case of lateral loading increased dramatically in comparison with the hollow composite configuration.