27 research outputs found
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Poly(ethylene terephthalate) glycol/carbon black composites for 4D printing
This research introduces PETG-CB (poly(ethylene terephthalate) glycol modified with carbon black) composites, a new class of shape memory polymers 4D printed using the Fused Deposition Modeling (FDM) method. Nanocomposites with varying concentrations of CB (0.5 %, 1 %, and 3 % by weight) are developed to enhance the functional performance of PETG in 4D printing applications. Comprehensive characterization at the micro- and macro-scale, including dynamic thermal mechanical analysis (DMTA), scanning electron microscopy (SEM), and mechanical testing, is employed to assess the viscoelastic behavior, microstructural integrity, and mechanical strength under thermal stimulation. Experimental results reveal that CB addition significantly alters the glass transition temperature and improves mechanical properties, with the 1 % CB composite demonstrating optimal tensile strength and enhanced shape memory effects. SEM analysis confirms a uniform distribution of CB particles, contributing to the improved mechanical properties and printability of the nanocomposites. The shape memory tests show excellent recovery rates above 97 %, with faster recovery observed in composites with higher CB content. These findings highlight the potential of PETG-CB composites in applications requiring rapid response and high mechanical performance, making them promising materials for future advancements in the 4D printing technology
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A new strategy for achieving shape memory effects in 4D printed two-layer composite structures
In this study, a new strategy and design for achieving a shape memory effect (SME) and 4D printed two-layer composite structures is unveiled, thanks to fused deposition modeling (FDM) biomaterial printing of commercial filaments, which do not have an SME. We used ABS and PCL as two well-known thermoplastics, and TPU as elastomer filaments that were printed in a two-layer structure. The thermoplastic layer plays the role of constraint for the elastomeric layer. A rubber-to-glass transition of the thermoplastic layer acts as a switching phenomenon that provides the capability of stabilizing the temporary shape, as well as storing the deformation stress for the subsequent recovery of the permanent shape by phase changing the thermoplastic layer in the opposite direction. The results show that ABS–TPU had fixity and recovery ratios above 90%. The PCL–TPU composite structure also demonstrated complete recovery, but its fixity was 77.42%. The difference in the SME of the two composite structures is related to the transition for each thermoplastic and programming temperature. Additionally, in the early cycles, the shape-memory performance decreased, and in the fourth and fifth cycles, it almost stabilized. The scanning electron microscopy (SEM) photographs illustrated superior interfacial bonding and part integrity in the case of multi-material 3D printing
Versatile algorithms for the computation of 2-point spatial correlations in quantifying material structure
Application of full set of two point correlation functions from a pair of 2D cut sections for 3D porous media reconstruction
Three dimensional reconstruction of porous media using limited statistical information has attracted a great interestin Earth sciences and petroleum engineering. In this study, a fast and reliable method for 3D reconstruction is proposed based on approximation of correlation functionsand phase recovery algorithm using one and two perpendicular cut sections. In the proposed method, initially, full set of two point correlation functions (TPCFs) are extracted from the cut sections. Afterwards, the TPCF vectors are decomposed and then averaged to improve the accuracy of the 3D-TPCFs approximation and improve the capabilities of the reconstruction procedure. To demonstrate the ability of the proposed method to deal with both connectivity and anisotropic issues existed in 3D reconstruction literature, Berea sandstone and a synthetic representative volume element (RVE) are used. Eventually, the reconstruction results of Berea sandstone and the synthetic RVEs are examined based on tortuosityvalues, autocorrelation function and also porositydistribution in comparison with their corresponding original RVEs. Evaluation of tortuosity values in the original and reconstructed RVEs for both Berea sandstone and the synthetic RVE reveals that for every axis of interest, there is a satisfactory agreement between the original and reconstructed RVEs realized using those two cut sections that contain the direction of interest as their common axis. This point indicates that the proposed approach which used two perpendicular cut sections provides more reliable and robust 3D reconstruction RVEs
Computational Elucidation of Elastic Percolation Threshold in Isotropic and Anisotropic Microstructures with Voronoi Tessellation
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Advancing sustainable shape memory polymers through 4D printing of polylactic acid-polybutylene adipate terephthalate blends
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