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Tunability of elastic modulus in 3D printed Shape memory polymer. Elastic modulus behavior as a function of programming level.
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Additive manufacturing has revolutionized the entire design cycle across a wide range of industries. The majority of materials utilized in 3D printing result in rather rigid structures with a fixed set of properties. Four-dimensional printing (4D printing) addresses this limitation by relaxing the geometric/properties rigidity over time. The carefu...
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... different sets of programming levels were conducted over a wide range of displacements, up to 10 mm. The tunability of elastic modulus is evident in the stress-strain curves shown in Figure 7. The results clearly highlight a non-linear relation between the elastic modulus and programming level with changes in moduli becoming less noticeable at the higher programming levels (i.e., ∆Lprog > 2mm). ...
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... should be noted that the experiments reported in Figure 7 were collected in a rather random order (0 mm→2 mm→4 mm→3 mm→10 mm→1 mm) in order to assure that any detectible correlations in properties are primarily attributed to different programming levels and not due to cyclic loading. ...
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... strains upon cycling and the programing process which alters the geometry of the multi-cell structure and the modulus of the SMP. The complex interaction between all of these different parameters has surprisingly limited the ability to tune structural stiffness through programing. Even with a simple dogbone configuration, the results shown in Fig. 7 highlight the non-linear modulus reduction with increasing programing levels. In case of the auxetic structure considered is this work, this interaction between geometric induced changes, which would increase the structural stiffness as the structure is transformed from concave to convex, and stretch/programing induced changes, which ...
Citations
... In another work, Yousuf et al. [28] utilize a thermoplastic shape-memory polymer (SMP) to 3D print an array of samples, including dogbone samples for testing and multicell and simple honeycomb structures. This particular polymer, which is suggested for deposition at a temperature of 200 °C, enables the fabrication of structures whose mechanical properties can be adjusted. ...
... Enhanced mechanical stability and environmental adaptability are results of the embedded metal structure, which qualifies the material for use in severe environments. The technology's versatility in flexible electronics and optoelectronic devices is exemplified through its use in resistive transparent strain Thermoplastic SMP FFF The study concludes that repeated programming and cycle loading significantly affect the mechanical properties of 4D printed structures due to residual strain accumulation, with cycle frequency and programming intensity influencing deterioration [28] Carbon/epoxy material -The fatigue resistance of a 24-inch specimen of 4D printed material through 175,000 cycles of three-point deformation is examined. It has been found that the spring constant remained consistent, highlighting the material's exceptional fatigue resistance [29] PLA FFF The fatigue resistance of stents varies with thickness, with 0.2 mm and 0.3 mm stents showing considerable resistance while the 0.4 mm stent exhibits reduced resistance [30] MASM DIW During cyclic endurance tests at 40% compression strain and 50% tensile strain, the 4D printed MASM displayed remarkable fatigue resistance [31] Hydrogel Femtosecond laser direct writing Multiple expansion and contraction cycles are utilized to determine the expansion ratio of the cubic plate to assess the fatigue resistance of the printed hydrogel [32] FTE LS EFD Microscale 3D Printing The resistance change of the sensor is assessed subjected to a strain rate of 60% for 1000 cycles to evaluate fatigue resistance [34] Content courtesy of Springer Nature, terms of use apply. ...
4D printing presents a new direction in additive manufacturing through the incorporation of the time dimension into objects, thereby empowering them to modify their shape, properties, or functioning in stimulus to external influences. It is critical to investigate the fatigue behavior of these materials to comprehend their durability and reliability in the context of repeated stress or environmental changes. However, there has been limited effort to study this phenomenon. The purpose of this literature review is to consolidate the current understanding of the fatigue properties of 4D printed materials and identify areas where research is lacking. The impact of this work is to establish a foundation through a literature review for advancements in material science and manufacturing research that can improve the understanding of the fatigue behavior of 4D printed materials.
... Reasonably architected design materials have novel mechanical behaviours that are difficult to achieve with traditional structures [24,25] With the development of 3D additive manufacturing technologies that have led to fabricate the complex structures possible in the last decade [26]. ...
... 4D printing, combining stimulus-responsive materials and 3D printing processes, offers an unprecedented way to personalize actively deformable and mechanically tunable cellular structures [19][20][21]. 4D printed objects can change their shape or properties over time in response to various external stimuli [22][23][24]. Recently, Bodaghi et al. [25,26] produced dual-material auxetic meta-sandwiches and re-entrant auxetic mechanical metamaterials with reversible energy absorption capability by fused filament fabrication (FFF) 4D printing technique. ...
The properties of functionally graded (FG) cellular structures vary spatially, and the varying properties can meet the requirements of different working environments. In this study, we fabricated FG cellular structures with shape memory effect by 4D printing and evaluated the compressive performance and shape memory behavior of these structures with temperature through experimental analysis and finite element simulations. The results show that the maximum energy absorption gradually decreases but the compressive modulus gradually increases with increasing gradient parameters. Moreover, the finite element simulations also show that the compressive deformation mode of the structure shifts from uniform to non-uniform deformation with increasing gradient parameters. The compressive modulus and compressive strength of 4D printed FG structures decrease with increasing temperature due to the influence of the shape memory polymer, and they exhibit outstanding shape recovery capability under high-temperature stimulus. The proposed 4D printed FG structures with such responsiveness to stimulus shed light on the design of intelligent energy-absorbing devices that meet specific functional requirements.
... And the impacts of angles and thickness on auxeticity of STL structures are investigated based on verified numerical simulations. It is of significance to provide a new perspective and theoretical basis for the multi-directional auxetic structures [61][62][63]. The proposed starshaped tubes possess the potential in civil engineering [64,65]. ...
... MEX technology is composed of three subclasses: i) pellet-based MEX (it is possible to use big area systems to extrude reinforced composites materials [1][2]), ii) liquidbased MEX (generally custom-made machines are used to extrude ink materials [3][4]), and iii) filament-based MEX (the most widespread technology, used to extrude a wide range of materials having different mechanical and electrical properties). The latter, has become popular for several advantages such as i) the possibility to extrude stiff and soft materials in the same printing cycle to create bio-inspired structures [5][6][7], ii) the possibility to fabricate smart objects equipped with 3D printed sensors [8][9], [10][11][12], iii) possibility to extrude energetic materials [12] , iv) possibility to fabricate auxetic structures [13][14][15], v) possibility to fabricate energy harvesting devices like batteries [16]. Filament-based MEX has been successfully employed in the soft robotics domain to fabricate different kinds of soft robots capable to perform several tasks such as grasping, jumping, crawling [17][18][19]. ...
Additive Manufacturing (AM) technologies have been extensively used for the fabrication of several soft robotics devices mostly based on pneumatic actuation systems and Shape Memory Materials (SMMs). Electromagnetic (EM)-based soft robots are still underexploited and results in several benefits such as cost-effectiveness, portability, no need of cooling systems and fast actuation. In the present research paper, a soft EM device has been fabricated using Material Extrusion (MEX) technology. The main contribution of this study is the vibration reduction of additively manufactured soft EM robots: the vibration has been reduced of 16% by using a joint composed of soft ribs. A Design of Experiment (DoE) approach has been used and rib orientation, thickness, and spacing has been studied. The reduction in vibration of soft EM robots, lays the foundation for the usage of MEX technology to fabricate this new appealing class of robots.KeywordsAdditive manufacturingsoft roboticselectromagnetic devicesmaterial extrusion
... The significant advances in additive manufacturing (AM) techniques of the last years have enabled the fabrication of mechanical metamaterials with an ever-increasing level of accuracy, attracting growing multidisciplinary interest and spanning different technological fields. Mechanical metamaterials have been the subject of numerous studies for their unconventional response to external actions (e.g., [1][2][3][4][5][6][7][8]), which makes them interesting for applications (e.g., [9,10]). A substantial part of the literature focused on the design and analysis of bistable/multistable structures and metamaterials, and it was amply demonstrated that mechanical instabilities can be exploited to store and release energy in order to obtain energy-trapping devices [11,12], stable propagation of solitary waves [13,14], actuators and soft robots [15,16]. ...
Recent developments in the quality and accuracy of additive manufacturing have drawn particular attention to metamaterials characterised by a multistable response to achieve exceptional mechanical properties. This work focuses on the design, fabrication, testing, and simulation of tensegrity-like lattice chains accomplishing a multistable behaviour. The chains are composed of chiral tensegrity-like units featuring a highly nonlinear bistable response with compression-twisting coupling. Different chains are designed by exploiting the chirality of the units and realised by the inverted stereolithography technique. Their mechanical response is experimentally characterised, demonstrating the attainment of the desired multistable behaviour. A predictive semi-analytical model is derived to reconstruct the multistable energy landscape and force-vs.-displacement curve of the whole chain. The presented chains may constitute a flexible platform for programmable materials, potentially extending to modular chains also based on other types of tensegrity-like units.
... In 1987, Lakes 1 first reported on the development of man-made negative Poisson's ratio materials, and since then, research works in auxetic structures have continued to evolve alongside advancements in additive manufacturing technology. [8][9][10][11][12][13][14] As an artificial porous material, auxetic cellular materials offer several advantages over traditional materials, including lightweightness, high energy absorption, and sound insulation properties. 5 Currently, auxetic materials find applications in various fields such as textile materials, 15 smart sensors, 16,17 protective mats, 18 and vibration dampers. ...
The use of metamaterial structures with auxeticity can result in exceptional mechanical properties, such as high energy absorption and fracture resistance. However, traditional design approaches rely heavily on researchers' subjective experiences, while existing inverse design methods limit design possibilities by ignoring generative diversity. In this study, we report a deep-learning-based inverse design approach for 3D auxetic unit cells that overcomes these limitations by providing diverse and accurately conditioned design options. We construct a dataset of symmetric 3D auxetic unit cells and apply an elastic modulus optimization network to generate diversified spatial topological structures with negative Poisson's ratios and optimized stiffness. The resulting 3D unit cells exhibit improved mechanical properties, as confirmed by finite element simulations and experiments. Our approach offers better coverage of the design space and generates optimized 3D unit cells with rich and diverse properties.
... Advanced research on 3DP dynamic shape-shifting has recently received attention as the next significant advance in AM methods [12]. In contrast to typical 3D-printed components, which are frequently stiff and static [13], 4DP is the next generation technology because of the merged dynamic behaviors inside the Smart Material (SM) [2]. 4DP dynamic structures with changeable shape modifications have attracted industrial interest, since they can provide advanced features such as self-assembly, self-repair, and self-adaptability [14]. ...
In a variety of industries, Additive Manufacturing has revolutionized the whole design–fabrication cycle. Traditional 3D printing is typically employed to produce static components, which are not able to fulfill dynamic structural requirements and are inappropriate for applications such as soft grippers, self-assembly systems, and smart actuators. To address this limitation, an innovative technology has emerged, known as “4D printing”. It processes smart materials by using 3D printing for fabricating smart structures that can be reconfigured by applying different inputs, such as heat, humidity, magnetism, electricity, light, etc. At present, 4D printing is still a growing technology, and it presents numerous challenges regarding materials, design, simulation, fabrication processes, applied strategies, and reversibility. In this work a critical review of 4D printing technologies, materials, and applications is provided.
... Additive manufacturing techniques have become ubiquitous in the engineering and industrial scenes. The growing dependence on them stems from their proven utility in fabricating components with very complex 3D geometries and from a wide range of materials [1][2][3][4][5][6]. Moreover, they eliminate the need for subtractive processes or molds, which allows them, particularly in nonmass production cases involving complex shapes, to deliver a simpler, faster, less expensive, and more sustainable manufacturing solution [7]. ...
... The properties of 3D-printed components can differ from those of their constituting filaments, as 3D printing processes can introduce defects, voids, and different types of heterogeneities [1,37]. This motivated investigating the mechanical properties of parts 3D printed using the reinforced filaments fabricated in this work. ...
Low-cost desktop-sized fused deposition modeling (FDM) printers have been widely embraced by small to large-scale institutions and individuals. To further enhance their utility and increase the range of materials that they can process, this work proposes a low-cost solution that adapts to low-cost desktop-sized extruders and enables them to fabricate filaments comprising a wide range of nonorganic reinforcing particles. This solution will fill a gap in the field, as low-cost fabrication techniques for reinforced filaments have been lacking. In the proposed solution, particles are heated and deposited on thermoplastic pellets to form a coating. Coated pellets are subsequently extruded using a low-cost desktop single-screw extruder. The effectiveness of the process is demonstrated by fabricating polylactic acid (PLA) filaments reinforced with two types of reinforcements, namely, dune sand and silicon carbide. Filaments’ stiffness and strength were measured, and their microstructure along their lateral and longitudinal directions were investigated. Improvements in tensile strength (up to 8%) and stiffness (up to 4.5%) were observed, but at low reinforcement levels (less than 2 wt%). Results showed that the proposed process could be used to fabricate filaments with multiple types of particles. The produced filaments were successfully used to fabricate 3D parts using a commercial desktop FDM printer.
... The significant advances in additive manufacturing (AM) techniques of the last years have enabled the fabrication of mechanical metamaterials with an ever-increasing level of accuracy, attracting growing multidisciplinary interest and spanning different technological fields. Mechanical metamaterials have been the subject of numerous studies for their 5 unconventional response to external actions (e.g., [1][2][3][4][5][6][7][8]), which makes them interesting for applications (e.g., [9,10]). A substantial part of the literature focused on the design and analysis of bistable/multistable structures and metamaterials, and it was amply demonstrated that mechanical instabilities can be exploited to store and release energy in order to obtain energy-trapping devices [11,12], stable propagation of solitary waves [13,14], 10 actuators and soft robots [15,16]. ...
