In this groundbreaking study, Polyethylene Terephthalate Glycol (PETG)-Fe3O4 nanocomposites were ... more In this groundbreaking study, Polyethylene Terephthalate Glycol (PETG)-Fe3O4 nanocomposites were developed for 4D printing, incorporating iron oxide (Fe3O4) nanoparticles into PETG matrix. The research contribution lies in its innovative approach to enhancing the shape memory effect (SME) through thermo-magnetic responsiveness, positioning PETG-Fe3O4 as a revolutionary material in smart additive manufacturing. The composites were synthesized using a melt mixing method, followed by 3D printing into specimens for comprehensive evaluation through dynamic mechanical thermal analysis (DMTA), scanning electron microscopy (SEM), and uniaxial tensile tests. The findings revealed that the incorporation of Fe3O4 nanoparticles significantly boosts the composites’ storage modulus and glass transition temperature, indicative of improved stiffness and thermal properties. Notably, the 15 % Fe3O4 composite emerged as the optimal blend, exhibiting the highest tensile strength and a favourable balance between mechanical integrity and flexibility. A key result was the enhanced SME under both thermal and magnetic stimuli, with recovery efficiency and speed escalating with nanoparticle concentration. This advancement underscores the potential of PETG-Fe3O4 nanocomposites in fabricating smart structures capable of environmental adaptability, paving the way for impacts in biomedical, aerospace, and robotic devices. Through this work, a new paradigm in material functionality for 4D printing has been established, demonstrating the viability of magnetic nanoparticle integration for added smart capabilities.
One of the major challenges in 4D printed Shape Memory Polymers (SMPs) is their slow response to ... more One of the major challenges in 4D printed Shape Memory Polymers (SMPs) is their slow response to thermal stimuli. Synthetic carbon fillers have been introduced to address this issue; however, their use comes with environmental concerns. On the other hand, Polylactic Acid (PLA) is commonly used for 3D/4D printing of SMPs, but it requires softening to achieve large deformations. This research paper introduces a sustainable solution through blending PLA with Polybutylene Adipate Terephthalate (PBAT) that not only addresses these challenges but also possesses environmental eco-friendliness due to PBAT's high biodegradability rate. PBAT with weight percentages of 15 %, 30 %, and 45 % is utilized to soften PLA, and their composites are successfully 4D printed. Mechanical properties, shape memory effects, morphology, and thermal behaviors are comprehensively investigated. The results show that blending PLA with 45 % PBAT weight results in excellent features such as 220 % elongation and 93 % shape recovery in just a few seconds. The other two PLA-PBAT blends achieve complete shape recovery in less than 8 s. The PLA-PBAT contains 15 % PBAT, in addition to high strength (40 MPa), has 17 % elongation. This, coupled with the low melting temperature of PBAT, drives the high shape recovery rate. Scanning electron microscopy images finally confirm the high printability of all three blends, with the PLA-PBAT composite containing 30 % PBAT exhibiting the best quality in layer interfaces and the least porosity.
In this article, the mechanical properties, microstructure, forming limit diagram (FLD) and aniso... more In this article, the mechanical properties, microstructure, forming limit diagram (FLD) and anisotropy of dual phase Mg-7Li-1Zn alloy have been evaluated by a uniaxial tensile test at three directions, scanning electron microscopy (SEM), optical microscopy (OM) and hemispherical punch test at ambient temperature. The optical microscopy images showed that the microstructure of as-cast LZ71 alloy possesses a dual phase microstructure such as β-Li matrix with bodycentered cubic (BCC) structure and a partitioned α-Mg phase with hexagonal closest packed (HCP) structure in lath shape. After rolling process, the α-Mg phase has been elongated and arranged in the rolling direction and anisotropy at different directions increased, but after full annealing, microstructure arranged more uniform and changed from elongated to the uniform structure which this is the factor that reflects the reduction of anisotropy. FLD shows the limiting surface strains that sheet metal can endure before the start of localized necking and fracture at different deformation modes in tension-tension and tension-compression loading paths. The FLD of Mg-7Li-1Zn showed that this material has desirable formability due to the BCC structure with high slip system in the ambient temperature. Also, the results of the tensile test matched with the Preprint of: Davood Rahmatabadi, Ramin Hashemi, Moslem tayyebi and Abbas Bayati. (2019). Investigation of mechanical properties, formability, and anisotropy of dual phase Mg-7Li-1Zn. Materials Research Express.
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