scholarly journals Viscoelastic Behaviour of Flexible Thermoplastic Polyurethane Additively Manufactured Parts: Influence of Inner-Structure Design Factors

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2365
Author(s):  
Fernández Pelayo ◽  
David Blanco ◽  
Pedro Fernández ◽  
Javier González ◽  
Natalia Beltrán
Keyword(s):  
Additive Manufacturing ◽  
Mechanical Behaviour ◽  
Flexible Electronics ◽  
Thermoplastic Polyurethane ◽  
Relaxation Modulus ◽  
Maxwell Model ◽  
Material Model ◽  
Structure Design ◽  
Material Extrusion ◽  
Design Factors

Material extrusion based additive manufacturing is used to make three dimensional parts by means of layer-upon-layer deposition. There is a growing variety of polymers that can be processed with material extrusion. Thermoplastic polyurethanes allow manufacturing flexible parts that can be used in soft robotics, wearables and flexible electronics applications. Moreover, these flexible materials also present a certain degree of viscoelasticity. One of the main drawbacks of material extrusion is that decisions related to specific manufacturing configurations, such as the inner-structure design, shall affect the final mechanical behaviour of the flexible part. In this study, the influence of inner-structure design factors upon the viscoelastic relaxation modulus, E(t), of polyurethane parts is firstly analysed. The obtained results indicate that wall thickness has a higher influence upon E(t) than other inner-design factors. Moreover, an inadequate combination of those factors could reduce E(t) to a small fraction of that expected for an equivalent moulded part. Next, a viscoelastic material model is proposed and implemented using finite element modelling. This model is based on a generalized Maxwell model and contemplates the inner-structure design. The results show the viability of this approach to model the mechanical behaviour of parts manufactured with material extrusion additive manufacturing.

scholarly journals Study of the interlayer adhesion and warping during material extrusion-based additive manufacturing of a carbon nanotube/biobased thermoplastic polyurethane nanocomposite

Polymer ◽  
2021 ◽  
pp. 123734
Author(s):  
María Virginia Candal ◽  
Itxaso Calafel ◽  
Mercedes Fernández ◽  
Nora Aranburu ◽  
Roberto Hernández Aguirresarobe ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Additive Manufacturing ◽  
Thermoplastic Polyurethane ◽  
Material Extrusion

scholarly journals Biofunctional Glycol-Modified Polyethylene Terephthalate and Thermoplastic Polyurethane Implants by Extrusion-Based Additive Manufacturing for Medical 3D Maxillofacial Defect Reconstruction

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1751
Author(s):  
Matthias Katschnig ◽  
Juergen Wallner ◽  
Thomas Janics ◽  
Christoph Burgstaller ◽  
Wolfgang Zemann ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Material Selection ◽  
Ex Vivo ◽  
Thermoplastic Polyurethane ◽  
Patient Specific ◽  
Ex Vivo Model ◽  
Manufacturing Method ◽  
Material Extrusion ◽  
Defect Reconstruction ◽  
Standard Implant

This work addresses the topic of extrusion-based additive manufacturing (filament-based material extrusion) of patient-specific biofunctional maxillofacial implants. The technical approach was chosen to overcome the shortcomings of medically established fabrication processes such as a limited availability of materials or long manufacturing times. The goal of the work was a successful fabrication of basic implants for defect reconstruction. The underlying vision is the implants’ clinic-internal and operation-accompanying application. Following a literature search, a material selection was conducted. Digitally prepared three-dimensional (3D) models dealing with two representative mandible bone defects were printed based on the material selection. An ex-vivo model of the implant environment evaluated dimensional and fitting traits of the implants. Glycol-modified PET (PETG) and thermoplastic polyurethane (TPU) were finally selected. These plastics had high cell acceptance, good mechanical properties, and optimal printability. The subsequent fabrication process yielded two different implant strategies: the standard implant made of PETG with a build-up rate of approximately 10 g/h, and the biofunctional performance implant with a TPU shell and a PETG core with a build-up rate of approximately 4 g/h. The standard implant is meant to be intraoperatively applied, as the print time is below three hours even for larger skull defects. Standard implants proved to be well fitting, mechanically stable and cleanly printed. In addition, the hybrid implant showed particularly cell-friendly behavior due to the chemical constitution of the TPU shell and great impact stability because of the crack-absorbing TPU/PETG combination. This biofunctional constellation could be used in specific reconstructive patient cases and is suitable for pre-operative manufacturing based on radiological image scans of the defect. In summary, filament-based material extrusion has been identified as a suitable manufacturing method for personalized implants in the maxillofacial area. A further clinical and mechanical study is recommended.

Strain and Age Effects on Behavior of a Concrete Pavement Joint Sealant Material

1996 ◽  
Vol 1529 (1) ◽  
pp. 95-100
Author(s):  
Ashok Gurjar ◽  
Dan G. Zollinger ◽  
Tianxi Tang
Keyword(s):  
Master Curve ◽  
Superposition Principle ◽  
Relaxation Modulus ◽  
Maxwell Model ◽  
Material Model ◽  
Concrete Pavement ◽  
Age Effects ◽  
Joint Analysis ◽  
Generalized Maxwell Model ◽  
Sealant Material

A one-part self-leveling silicone joint sealant material was experimentally investigated in the laboratory. It was found that strain and age had apparent effects on the relaxation modulus of the material. Relaxation tests were conducted under different strain levels. The test samples were exposed to ultraviolet radiation and moisture for artificial aging before testing. For this largely deformable material, finite strain formulas were used in analysis of experimental data. Strain and age effects were successfully normalized in the relaxation master curve by using the superposition principle. On the basis of the master curve, a material model of the generalized Maxwell model in parallel type was constructed. The real time was scaled to the reduced time by time-strain shift and time-age shift factors so as to characterize the strain and age effects. This model is mathematically simple and can be easily applied in finite element programs for concrete pavement joint analysis.

Multi-material model for the simulation of powder bed fusion additive manufacturing

2021 ◽  
Vol 194 ◽  
pp. 110415
Author(s):  
Vera E. Küng ◽  
Robert Scherr ◽  
Matthias Markl ◽  
Carolin Körner
Keyword(s):  
Additive Manufacturing ◽  
Material Model ◽  
Powder Bed Fusion ◽  
Powder Bed

A study on additive manufacturing build parameters as bonded joint design factors

2021 ◽  
pp. 1-30
Author(s):  
L. Bergonzi ◽  
A. Pirondi ◽  
F. Moroni ◽  
M. Frascio ◽  
M. Avalle
Keyword(s):  
Additive Manufacturing ◽  
Joint Design ◽  
Bonded Joint ◽  
Design Factors

EXPERIMENTAL RESEARCH ON VISCOELASTICITY PROPERTY OF DIFFERENT LAYERS PERIODONTAL LIGAMENT UNDER COMPRESSION

2021 ◽  
pp. 2150050
Author(s):  
JINLAI ZHOU ◽  
YANG SONG ◽  
CHENGUANG XU ◽  
CHUNQIU ZHANG ◽  
XUE SHI
Keyword(s):  
Elastic Modulus ◽  
Periodontal Ligament ◽  
Creep Compliance ◽  
Relaxation Modulus ◽  
Maxwell Model ◽  
Kelvin Model ◽  
Generalized Maxwell Model ◽  
Relaxation Stress ◽  
Generalized Kelvin Model ◽  
Fitting Accuracy

The periodontal ligament (PDL) exhibits different material mechanical properties along the long axis of the teeth. To explore the creep and the relaxation effects of dissimilar layers of PDL, this paper took the central incisors of porcine mandibular as experimental subjects and divided them perpendicular to the teeth axis into five layers. Creep experiments and relaxation experiments on five layers were conducted to obtain the creep compliance and relaxation modulus at different layers. Linear elastic model, generalized Kelvin model, and generalized Maxwell model were used to describe the major characteristics of the PDL: Instantaneous elasticity, creep and relaxation. Fitting accuracy of three-parameter, five-parameter, and seven-parameter of the model was compared, and the constitutive equations of different layers were established by the least square method. The results presented that the creep strain and the relaxation stress of PDL were exponentially correlated with time under different loading conditions. Different layers showed a significant effect on the creep strain and relaxation stress of PDL. Along the long axis of the teeth, the changing rule of the creep compliance and relaxation modulus of each layer showed quite the contrary, and the instantaneous elastic modulus first decreased to the minimum, then increased to the maximum. Higher instantaneous elastic modulus led to lower creep compliance and higher relaxation modulus. The generalized Kelvin model and the generalized Maxwell model well characterized the creep and relaxation properties of PDL. Fitting accuracy increased with the number of model parameters. The relaxation time of PDL was about one order of magnitude shorter than the creep retardation time, which indicated that the relaxation effect lasted shorter than the creep effect.

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