scholarly journals Additively Manufactured Absorbable Porous Metal Implants – Processing, Alloying and Corrosion Behavior

2021 ◽  
Vol 8 ◽  
Author(s):  
Holger Jahr ◽  
Yageng Li ◽  
Jie Zhou ◽  
Amir A. Zadpoor ◽  
Kai-Uwe Schröder
Keyword(s):  
Mechanical Properties ◽  
Bone Regeneration ◽  
Structural Integrity ◽  
Bone Cells ◽  
Healing Process ◽  
Regeneration Ability ◽  
Porous Metals ◽  
Geometrical Design ◽  
Metal Implants ◽  
The Impact

Treating large bone defects is still a clinical challenge without perfect solution, mainly due to the unavailability of suitable bone implants. Additively manufactured (AM) absorbable porous metals provide unparalleled opportunities to realize the challenging requirements for bone-mimetic implants. Firstly, multi-scale geometries of such implants can be customized to mimic the micro-architecture and mechanical properties of human bone. The interconnected porous structure additionally increases the surface area to facilitate adhesion and proliferation of bone cells. Finally, their absorption properties are tunable to maintain the structural integrity of the implant throughout the bone healing process, ensuring sufficient loadbearing when needed and full disintegration after their job is done. Such a combination of properties paves the way for complete bone regeneration and remodeling. It is important to thoroughly characterize the biodegradation behavior, mechanical properties, and bone regeneration ability when developing ideal porous absorbable metal implants. We review the state-of-the-art of absorbable porous metals manufactured by selective laser melting (SLM), with a focus on geometrical design, material type, processing, and post-treatment. The impact of the latter aspects on absorption behavior, resulting mechanical properties, and cytocompatibility will also be briefly discussed. In comparison to their solid inert counterparts, AM absorbable porous metals (APMs) have shown many unique properties and hold tremendous potential to further optimize their application-specific performance due to their flexible geometrical design. We further highlight challenges in adopting AM APMs for future Orthopedic solutions.

scholarly journals A novel MRI compatible mouse fracture model to characterize and monitor bone regeneration and tissue composition

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Nina Schmitz ◽  
Melanie Timmen ◽  
Katharina Kostka ◽  
Verena Hoerr ◽  
Christian Schwarz ◽  
...  
Keyword(s):  
Fracture Healing ◽  
Bone Regeneration ◽  
Cell Attachment ◽  
Healing Process ◽  
Living Organism ◽  
Fracture Site ◽  
Tissue Composition ◽  
Metal Implants ◽  
Callus Tissues

Abstract Over the last years, murine in vivo magnetic resonance imaging (MRI) contributed to a new understanding of tissue composition, regeneration and diseases. Due to artefacts generated by the currently used metal implants, MRI is limited in fracture healing research so far. In this study, we investigated a novel MRI-compatible, ceramic intramedullary fracture implant during bone regeneration in mice. Three-point-bending revealed a higher stiffness of the ceramic material compared to the metal implants. Electron microscopy displayed a rough surface of the ceramic implant that was comparable to standard metal devices and allowed cell attachment and growth of osteoblastic cells. MicroCT-imaging illustrated the development of the callus around the fracture site indicating a regular progressing healing process when using the novel implant. In MRI, different callus tissues and the implant could clearly be distinguished from each other without any artefacts. Monitoring fracture healing using MRI-compatible implants will improve our knowledge of callus tissue regeneration by 3D insights longitudinal in the same living organism, which might also help to reduce the consumption of animals for future fracture healing studies, significantly. Finally, this study may be translated into clinical application to improve our knowledge about human bone regeneration.

scholarly journals The impact of fibre processing on the mechanical properties of epoxy matrix composites and wood-based particleboard reinforced with hemp (Cannabis sativa L.) fibre

2022 ◽  
Author(s):  
Albert Hernandez-Estrada ◽  
Jörg Müssig ◽  
Mark Hughes
Keyword(s):  
Mechanical Properties ◽  
Fracture Zone ◽  
Structural Integrity ◽  
Bending Strength ◽  
Cannabis Sativa ◽  
Mechanical Performance ◽  
Epoxy Composites ◽  
Fibre Reinforcement ◽  
Fibre Bundles ◽  
The Impact

AbstractThis work investigated the impact that the processing of hemp (C. sativa L.) fibre has on the mechanical properties of unidirectional fibre-reinforced epoxy resin composites loaded in axial tension, and particleboard reinforced with aligned fibre bundles applied to one surface of the panel. For this purpose, mechanically processed (decorticated) and un-processed hemp fibre bundles, obtained from retted and un-retted hemp stems, were utilised. The results clearly show the impact of fibre reinforcement in both materials. Epoxy composites reinforced with processed hemp exhibited 3.3 times greater tensile strength when compared to the un-reinforced polymer, while for the particleboards, the bending strength obtained in those reinforced with processed hemp was 1.7 times greater than the un-reinforced particleboards. Moreover, whether the fibre bundles were processed or un-processed also affected the mechanical performance, especially in the epoxy composites. For example, the un-processed fibre-reinforced epoxy composites exhibited 49% greater work of fracture than the composites reinforced with processed hemp. In the wood-based particleboards, however, the difference was not significant. Additionally, observations of the fracture zone of the specimens showed different failure characteristics depending on whether the composites were reinforced with processed or un-processed hemp. Both epoxy composites and wood-based particleboards reinforced with un-processed hemp exhibited fibre reinforcement apparently able to retain structural integrity after the composite’s failure. On the other hand, when processed hemp was used as reinforcement, fibre bundles showed a clear cut across the specimen, with the fibre-reinforcement mainly failing at the composite's fracture zone.

Polylactide/polycaprolactone asymmetric membranes for guided bone regeneration

e-Polymers ◽  
2016 ◽  
Vol 16 (5) ◽  
pp. 351-358 ◽  
Author(s):  
Patrycja Domalik-Pyzik ◽  
Anna Morawska-Chochół ◽  
Jan Chłopek ◽  
Izabella Rajzer ◽  
Agata Wrona ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bone Regeneration ◽  
Freeze Drying ◽  
Bone Cells ◽  
Water Environment ◽  
Guided Bone Regeneration ◽  
Tissue Growth ◽  
Drying Methods ◽  
Asymmetric Membranes ◽  
Resorbable Polymers

AbstractThe aim of this work was to develop bioresorbable, asymmetric membranes for guided bone regeneration (GBR). Two resorbable polymers – polylactide (PLA) and polycaprolactone (PCL) were used in fabrication process. Two different manufacturing methods were applied: electrospinning in the case of PLA and freeze-drying of PCL. Mechanical properties, stability in a water environment and biocompatibility of fabricated membranes were evaluated. Microstructure [scanning electron microscopy (SEM)] of the membranes was assessed in terms of level of porosity, as well as size and shape of the pores. Study showed that combination of electrospinning and freeze-drying methods allows biocompatible PLA/PCL bi-phasic materials of appropriate mechanical properties and diverse microstructure to be produced, that should on the one hand prevent soft tissue growth, and on the other hand be a suitable scaffold for the growth of bone cells.

NUMERICAL SIMULATION OF APPARENT DENSITY EVOLUTION OF TRABECULAR BONE UNDER FATIGUE LOADING: EFFECT OF BONE INITIAL PROPERTIES

2019 ◽  
Vol 19 (05) ◽  
pp. 1950041
Author(s):  
ABDELWAHED BARKAOUI ◽  
RABEB BEN KAHLA ◽  
TAREK MERZOUKI ◽  
RIDHA HAMBLI
Keyword(s):  
Mechanical Properties ◽  
Cyclic Loading ◽  
Trabecular Bone ◽  
Structural Integrity ◽  
Numerical Study ◽  
Fatigue Loading ◽  
Mechanical Stimuli ◽  
Mineral Density ◽  
Normal Loading ◽  
The Impact

Bone remodeling is a physiological phenomenon coupling resorption and formation processes that are mainly mediated by osteoclasts and osteoblasts, in response to mechanical stimuli transduced by osteocytes to biochemical signals activating the bone multicellular unit. Under normal loading conditions, bone resorption and formation are balanced by a homeostasis process. When bone is subjected to overstress, microdamaging occurs, which induces a modification of the structural integrity and microarchitecture. This has drawn significant attention to the mechanical properties of bone. In this context, the current study has been carried out with the aim of numerically investigating the impact of the mechanical properties on the remodeling process of the trabecular bone under cyclic loading, highlighting the effects of different values of the mineral density and the Young’s modulus. This was performed using a mechanobiological model, coupling mechanical and biological approaches, allowing to numerically simulate the effect of the selected parameters for a 20-year-period of cyclic loading for 2D and 3D models of a human femur head. The current work is an explorative numerical study, and the obtained results revealed the changes in the overall stiffness of the bone according to the mechanical properties.

scholarly journals Ex Vivo Dermis Mechanical Behavior in Relation to Decellularization Treatment Length

2016 ◽  
Vol 10 (1) ◽  
pp. 34-42 ◽  
Author(s):  
Mara Terzini ◽  
Cristina Bignardi ◽  
Carlotta Castagnoli ◽  
Irene Cambieri ◽  
Elisabetta M. Zanetti ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Sodium Hydroxide ◽  
Structural Properties ◽  
Structural Integrity ◽  
Ex Vivo ◽  
Tensile Tests ◽  
Treatment Length ◽  
Native Tissue ◽  
The Impact

Background: The dermis is a commonly used source tissue for biologic scaffolds; all cellular and nuclear materials need to be removed to limit the inflammatory immune response by the host organism. The decellularization is critical because it must preserve the structural integrity of the extracellular matrix. This work has analyzed a decellularization procedure commonly followed for the dermal tissue that is a chemical treatment with sodium hydroxide. The goal of this work is to identify the optimal treatment length on the basis of structural properties. Methods: Tensile tests have been performed on the native tissue and on tissues decellularized for 1-7 weeks in sodium hydroxide. The collected data have been analyzed through Tukey-Kramer test to assess if the mechanical properties (ultimate tensile stress and elastic modulus) of decellularized tissues were significantly different from the properties of the native tissue. These tests have been performed on specimens cut along two orthogonal directions (parallel and perpendicular to Langer’s lines). Results: The decellularization treatment performed with sodium hydroxide in general weakens the tissue: both the ultimate stress and the elastic modulus get lower. The structural properties along Langer lines orientation are more strongly impacted, while the structural properties orthogonal to Langer lines can be preserved with an optimal duration of the decellularization treatment that is 5-6 weeks. Conclusion: The duration of the decellularization treatment is critical not only to reach a complete decellularization, but also to preserve the mechanical properties of the tissue; 5-6 week treatment performed with sodium hydroxide allows preserving the mechanical properties of the native tissue perpendicularly to Langer lines orientation, and minimizing the impact of the decellularization process on the mechanical properties along the Langer lines orientation.

Corrosion damage evolution of the aircraft aluminum alloy 2024 T3

2016 ◽  
Vol 7 (1) ◽  
pp. 25-46 ◽  
Author(s):  
Spiros Pantelakis ◽  
Dorothea Setsika ◽  
Apostolos Chamos ◽  
Anna Zervaki
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Damage Evolution ◽  
Structural Integrity ◽  
Corrosion Damage ◽  
Tensile Tests ◽  
Content Type ◽  
Experimental Database ◽  
Aluminum Alloy 2024 ◽  
The Impact

Purpose – The purpose of this paper is to quantify the corrosion damage evolution that has occurred on the aircraft aluminum alloy 2024 after the exposure to Exfoliation Corrosion Test (EXCO) solution. Moreover, the effect of the evolving corrosion damage on the materials mechanical properties has been assessed. The relevance of the corrosion damage induced by the exposure to the laboratory EXCO for linking it to the damage developed after the exposure of the material on several outdoor corrosive environments or in service is discussed. Design/methodology/approach – To induce corrosion damage the EXCO has been used. For the quantification of corrosion damage the metallographic features considered have been pit depth, diameter, pitting density and pit shape. The effect of the evolving corrosion damage on the materials mechanical properties has been assessed by means of tensile tests on pre corroded specimens. Findings – The results have shown that corrosion damage starts from pitting and evolves to exfoliation, after the development of intergranular corrosion. This evolution is expressed by the increase of the depth of attack, as well as through the significant growth of the diameter of the damaged areas. The results of the tensile tests performed on pre corroded material made an appreciable decrease of the materials tensile properties evident. The decrease of the tensile ductility may become dramatic and increases on severity with increasing corrosion exposure time. SEM fractography revealed a quasi-cleavage zone beneath the depth of corrosion attack. Originality/value – The results underline the impact of corrosion damage on the mechanical behavior of the aluminum alloy 2024 T3 and demonstrate the need for further investigation of the corrosion effect on the structural integrity of the material. This work provides an experimental database concerning the quantification of corrosion damage evolution and the loss of material properties due to corrosion.

The Impact of Corrosion on the Mechanical Behavior of Bolt

2010 ◽  
Vol 168-170 ◽  
pp. 408-411
Author(s):  
Xiao Yong Li
Keyword(s):  
Mechanical Properties ◽  
Experimental Investigation ◽  
Corrosion Test ◽  
Laboratory Tests ◽  
Structural Integrity ◽  
Mechanical Performance ◽  
Rock Bolt ◽  
Before And After ◽  
The Impact ◽  
Strength And Ductility

Corrosion is a negative contributor on the structural integrity of rock bolt and leads to degradation of the mechanical properties of steel rock bolt. Exposure to chloride, seawater, salt and saltwater and deicing chemical environments influences rock bolt and weakens it. In order to evaluate the influence of corrosion and the size of the steel on the mechanical properties of rock bolt, an experimental investigation was conducted on rock bolt whose rebar is 8, 12, 16, and 18 mm diameter, and which were artificially corroded for 10, 20, 30, 45, 60, 90, and 120 days. By the simulation corrosion test of loaded and unloaded bolts in Na2SO4 solution, the relation curves of the mechanical performance with the corrosive conditions and the corrosion time are given. The mechanical performance is compared between these two types of bolts. At the same time, the influential trend of the load on the mechanical performance of the corroded bolt is analyzed. The laboratory tests suggest that corrosion duration and rebar size had a significant impact on the strength and ductility degradation of the specimens. after being corroded in Na2SO4 solution, both the ultimate bearing capacity and the maximal tensility of loaded bolt decrease far more than those of unloaded bolt, and the endurance and service life of loaded bolt will also be shortened much more severely. The tensile mechanical properties before and after corrosion indicated progressive variation and drastic drop in their values.

The Impact of Corrosion on the Mechanical Properties of Smooth Steel Rebar HPB235

2011 ◽  
Vol 179-180 ◽  
pp. 28-31
Author(s):  
Xiao Yong Li ◽  
Zhi Gang Zhang
Keyword(s):  
Mechanical Properties ◽  
Experimental Investigation ◽  
Laboratory Tests ◽  
Structural Integrity ◽  
Strength Degradation ◽  
Progressive Reduction ◽  
Steel Rebar ◽  
Steel Bars ◽  
Before And After ◽  
The Impact

The Impact of Corrosion on the Mechanical Properties of Smooth Steel Rebar HPB235 The impact of corrosion on the mechanical properties of steel rebar was examined. An experimental investigation was carried out in order to gain better insight of the effect of corrosion on the mass loss, strength, of smooth Steel Rebar HPB235 10 mm diameter steel bars that were artificially corroded for different corrosion levels. Corrosion is a negative contributor on the structural integrity of concrete structures and leads to degradation of the mechanical properties of steel rebar. In order to evaluate the influence of corrosion on the mechanical properties of steel rebar, an experimental investigation was conducted on smooth steel rebar of 10 mm diameters, and which were artificially corroded for 1, 3, 5 and 7 months. The laboratory tests suggest that corrosion duration had a significant impact on the strength degradation of the specimens. The mechanical properties of tensile test before and after corrosion indicated progressive variation and drastic drop in their values. The corrosion enhanced the damage and created pits and notches, resulting in stress concentration points and progressive reduction of strength. It gets the express formula nominal ultimate strength and nominal yield strength.

scholarly journals Resolving Macrophages Counter Osteolysis by Anabolic Actions on Bone Cells

2018 ◽  
Vol 97 (10) ◽  
pp. 1160-1169 ◽  
Author(s):  
A. Viniegra ◽  
H. Goldberg ◽  
Ç. Çil ◽  
N. Fine ◽  
Z. Sheikh ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Bone Cells ◽  
Healing Process ◽  
Phenotypic Changes ◽  
Proinflammatory Mediators ◽  
Ppar Γ ◽  
Inflammatory Macrophages ◽  
The Impact

Progression of inflammatory osteolytic diseases, including rheumatoid arthritis and periodontitis, is characterized by increased production of proinflammatory mediators and matrix-degrading enzymes by macrophages and increased osteoclastic activity. Phenotypic changes in macrophages are central to the healing process in virtually all tissues. Using a murine model of periodontitis, we assessed the timing of macrophage phenotypic changes and the impact of proresolving activation during inflammatory osteolysis and healing. Proinflammatory macrophage activation and TNF-α overproduction within 3 wk after induction of periodontitis was associated with progressing bone loss. Proresolving activation within 1 wk of stimulus removal and markers of resolving macrophages (IL-10, TGF-β, and CD206) correlated strongly with bone levels. In vivo macrophage depletion with clodronate liposomes prevented bone resorption but impaired regeneration. Induction of resolving macrophages with rosiglitazone, a PPAR-γ agonist, led to reduced bone resorption during inflammatory stimulation and increased bone formation during healing. In vitro assessment of primary bone marrow–derived macrophages activated with either IFN-γ and LPS (proinflammatory activation) or IL-4 (proresolving activation) showed that IL-4-activated cells have enhanced resolving functions (production of anti-inflammatory cytokines; migration and phagocytosis of aged neutrophils) and exert direct anabolic actions on bone cells. Cystatin C secreted by resolving but not inflammatory macrophages explained, in part, the macrophage actions on osteoblasts and osteoclasts. This study supports the concept that therapeutic induction of proresolving functions in macrophages can recouple bone resorption and formation in inflammatory osteolytic diseases.

scholarly journals Process control testing for fused filament fabrication

2017 ◽  
Vol 23 (2) ◽  
pp. 246-256 ◽  
Author(s):  
Stephen Oluwashola Akande ◽  
Kenny Dalgarno ◽  
Javier Munguia
Keyword(s):  
Mechanical Properties ◽  
Impact Test ◽  
Structural Integrity ◽  
Fused Filament Fabrication ◽  
Influence Of Process Parameters ◽  
Content Type ◽  
Machine Performance ◽  
And Control ◽  
The Impact

Purpose The purpose of this research is to determine what tests can be most useful in quality assurance and control when using fused filament fabrication (FFF) 3D printing machines. The quality of the bond between layers is critical for the structural integrity of the fused filament fabricated parts. Design/methodology/approach Therefore, to determine the influence of process parameters on the quality of parts’ tensile, flexural, notched and un-notched impact, test specimens were fabricated in polylactic acid (PLA) using FFF with different layer thicknesses, fill densities, orientation and print speeds. The mechanical properties were then assessed along with the accuracy and mass of the samples. Findings It is concluded that a notched impact test gives a measure of interlayer bond strength which can be used across build styles to track machine performance, and that this, together with the mass and dimensions of the impact-test specimens, offers an appropriate set of tests capable of tracking the mechanical properties of parts produced using the FFF technique. Originality/value Therefore, this research finding will be of value in benchmarking FFF machines for quality parts fabrications.

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