Inverse Analysis of Three-Point Bending Tests for 3D Printed Fibre Reinforced Mortars

This study addresses the mechanical behavior of lattice materials based on flexible thermoplastic polyurethane (TPU) with honeycomb and gyroid architecture fabricated by 3D printing. Tensile, compression, and three-point bending tests were chosen as mechanical testing methods. The honeycomb architecture was found to provide higher values of rigidity (by 30%), strength (by 25%), plasticity (by 18%), and energy absorption (by 42%) of the flexible TPU lattice compared to the gyroid architecture. The strain recovery is better in the case of gyroid architecture (residual strain of 46% vs. 31%). TPUs with honeycomb architecture are characterized by anisotropy of mechanical properties in tensile and three-point bending tests. The obtained results are explained by the peculiarities of the lattice structure at meso- and macroscopic level and by the role of the pore space.

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Development of a Novel X-ray Compatible 3D-Printed Bone Model to Characterize Different K-Wire Fixation Methods in Support of the Treatment of Pediatric Radius Fractures

Polymers ◽

10.3390/polym13234179 ◽

2021 ◽

Vol 13 (23) ◽

pp. 4179

Author(s):

Anna Gabriella Lamberti ◽

Zoltan Ujfalusi ◽

Roland Told ◽

Dániel Hanna ◽

Gergő Józsa ◽

...

Keyword(s):

Standard Deviation ◽

Single Wire ◽

Bending Tests ◽

Parallel Wire ◽

X Ray ◽

Three Point Bending ◽

Fixation Methods ◽

Relative Standard ◽

Wire Fixation ◽

3D Printed

Additive manufacturing technologies are essential in biomedical modeling and prototyping. Polymer-based bone models are widely used in simulating surgical interventions and procedures. Distal forearm fractures are the most common pediatric fractures, in which the Kirschner wire fixation is the most widely used operative method. However, there is still lingering controversy throughout the published literature regarding the number of wires and sites of insertion. This study aims to critically compare the biomechanical stability of different K-wire fixation techniques. Different osteosyntheses were reconstructed on 189 novel standardized bone models, which were created using 3D printing and molding techniques, using PLA and polyurethane materials, and it has been characterized in terms of mechanical behavior and structure. X-ray imaging has also been performed. The validation of the model was successful: the relative standard deviations (RSD = 100 × SD × mean−1, where RSD is relative standard deviation, SD is the standard deviation) of the mechanical parameters varied between 1.1% (10° torsion; 6.52 Nm ± 0.07 Nm) and 5.3% (5° torsion; 4.33 Nm ± 0.23 Nm). The simulated fractures were fixed using two K-wires inserted from radial and dorsal directions (crossed wire fixation) or both from the radial direction, in parallel (parallel wire fixation). Single-wire fixations with shifted exit points were also included. Additionally, three-point bending tests with dorsal and radial load and torsion tests were performed. We measured the maximum force required for a 5 mm displacement of the probe under dorsal and radial loads (means for crossed wire fixation: 249.5 N and 355.9 N; parallel wire fixation: 246.4 N and 308.3 N; single wire fixation: 115.9 N and 166.5 N). We also measured the torque required for 5° and 10° torsion (which varied between 0.15 Nm for 5° and 0.36 Nm for 10° torsion). The crossed wire fixation provided the most stability during the three-point bending tests. Against torsion, both the crossed and parallel wire fixation were superior to the single-wire fixations. The 3D printed model is found to be a reliable, cost-effective tool that can be used to characterize the different fixation methods, and it can be used in further pre-clinical investigations.

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Infill Designs for 3D-Printed Shape-Memory Objects

Technologies ◽

10.3390/technologies9020029 ◽

2021 ◽

Vol 9 (2) ◽

pp. 29

Author(s):

Daniel Koske ◽

Andrea Ehrmann

Keyword(s):

Shape Memory ◽

Low Temperatures ◽

Shape Memory Polymers ◽

Poly Lactic Acid ◽

Protective Equipment ◽

Bending Tests ◽

Three Point Bending ◽

Long Time ◽

3D Printed ◽

Recovery Cycles

Shape-memory polymers (SMPs) can be deformed, cooled down, keeping their new shape for a long time, and recovered into their original shape after being heated above the glass or melting temperature again. Some SMPs, such as poly(lactic acid) (PLA), can be 3D printed, enabling a combination of 3D-printed shapes and 2D-printed, 3D-deformed ones. While deformation at high temperatures can be used, e.g., to fit orthoses to patients, SMPs used in protective equipment, bumpers, etc., are deformed at low temperatures, possibly causing irreversible breaks. Here, we compare different typical infill patterns, offered by common slicing software, with self-designed infill structures. Three-point bending tests were performed until maximum deflection as well as until the maximum force was reached, and then the samples were recovered in a warm water bath and tested again. The results show a severe influence of the infill pattern as well as the printing orientation on the amount of broken bonds and thus the mechanical properties after up to ten test/recovery cycles.

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Investigation of the Deformation Twins on the Bending Cross Section of TA2 Titanium Sheet

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.837.41 ◽

2020 ◽

Vol 837 ◽

pp. 41-45

Author(s):

Shuai Sun ◽

Kai Hua Liu

Keyword(s):

Electron Backscatter Diffraction ◽

Testing Machine ◽

Pure Titanium ◽

Titanium Sheet ◽

Bending Tests ◽

Three Point Bending ◽

Deformation Twins ◽

Ebsd Technique ◽

Backscatter Diffraction ◽

Deformation Area

In order to determine the evolution features of deformation twins for TA2 commercial pure titanium (cp-TA2), the TA2 samples were bent under different bending angles in three-point bending tests via a universal testing machine. The electron backscatter diffraction (EBSD) technique was applied to identify the grain boundaries (GBs) and twin boundaries (TBs) in the bending areas. The results reveal that the type of deformation area would effect the evolution of different deformation twins. It is inferred that the state of stress would promote the multiplication of the same type of deformation twins.

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A Study of the Flexural Behavior of Fiber-Reinforced Concretes Exposed to Moderate Temperatures

Materials ◽

10.3390/ma14133522 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3522

Author(s):

Marta Caballero-Jorna ◽

Marta Roig-Flores ◽

Pedro Serna

Keyword(s):

Steel Fiber ◽

Flexural Behavior ◽

Polypropylene Fibers ◽

Fiber Reinforced ◽

Insulation System ◽

Bending Tests ◽

Synthetic Fibers ◽

Three Point Bending ◽

Lower Performance ◽

Cracked Specimens

The use of synthetic fibers in fiber-reinforced concretes (FRCs) is often avoided due to the mistrust of lower performance at changing temperatures. This work examines the effect of moderate temperatures on the flexural strengths of FRCs. Two types of polypropylene fibers were tested, and one steel fiber was employed as a reference. Three-point bending tests were carried out following an adapted methodology based on the standard EN 14651. This adapted procedure included an insulation system that allowed the assessment of FRC flexural behavior after being exposed for two months at temperatures of 5, 20, 35 and 50 °C. In addition, the interaction of temperature with a pre-cracked state was also analyzed. To do this, several specimens were pre-cracked to 0.5 mm after 28 days and conditioned in their respective temperature until testing. The findings suggest that this range of moderate temperatures did not degrade the behavior of FRCs to a great extent since the analysis of variances showed that temperature is not always a significant factor; however, it did have an influence on the pre-cracked specimens at 35 and 50 °C.

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Utilization of Dacite as Alternative Aggregate in Asphalt Mixture

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.509.209 ◽

2012 ◽

Vol 509 ◽

pp. 209-214

Author(s):

Shao Peng Wu ◽

Pan Pan ◽

Ming Yu Chen

Keyword(s):

Asphalt Mixture ◽

Asphalt Mixtures ◽

Major Objective ◽

Widespread Application ◽

Bending Tests ◽

Three Point Bending ◽

Large Numbers ◽

Asphalt Content ◽

The Cost ◽

Cost Of Construction

With the widespread application of asphalt mixture, current demand from transportation managers for construction and maintenance of their pavement network consumes large numbers of aggregates. If agencies excessively favor to some certain kinds of excellent aggregates, the cost of construction could be considerably expensive. The major objective of this study is to determine the feasibility of utilizing dacite in asphalt mixtures. By means of Marshall, freeze-thaw, rutting and three-point bending tests, the performances of dacite and basalt asphalt mixture are compared. The results of the testing illustrate that dacite asphalt mixture is more susceptible to gradation and asphalt content than basalt asphalt mixture. Meanwhile it is showed that the performances of dacite asphalt mixture can be improved greatly with the involvement of additives including active mineral powder and cement. Furthermore, it is validated that dacite can be used as alternative aggregate in asphalt mixture.

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