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fracture toughness

Livia C Natale, Marcela C Rodrigues, Yvette Alania, Marina D S Chiari, Leticia C C Boaro, Marycel Cotrim, Oscar Vega, Roberto R Braga
OBJECTIVE: to verify the effect of the addition of dicalcium phosphate dihydrate (DCPD) particles functionalized with di- or triethylene glycol dimethacrylate (DEGDMA or TEGDMA) on the degree of conversion (DC), post-gel shrinkage (PS), mechanical properties, and ion release of experimental composites. METHODS: Four composites were prepared containing a BisGMA/TEGDMA matrix and 60 vol% of fillers. The positive control contained only barium glass fillers, while in the other composites 15 vol% of the barium was replaced by DCPD...
May 18, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Shichao Yue, Junling Wu, Qiang Zhang, Ke Zhang, Michael D Weir, Satoshi Imazato, Yuxing Bai, Hockin H K Xu
OBJECTIVES: Secondary caries at the tooth-restoration margins is a primary reason for restoration failure. Cracks at the margins lead to leakage which can trap bacteria, producing acids to cause caries. To date, there has been no report on developing an adhesive resin that has self-healing, antibacterial and remineralizing capabilities. The objectives of this study were to: (1) develop the first self-healing adhesive with antimicrobial and remineralizing capabilities, and (2) investigate the effects of incorporating microcapsules, dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) for the first time...
May 18, 2018: Journal of Dentistry
Dezhi Gao, Jie Jing, Jincheng Yu, Xue Guo, Yubai Zhang, Hongyu Gong, Yujun Zhang
B4 C ceramics with different contents of graphene platelets (GPL) were synthesized by a pressureless process in Ar atmosphere. The influences of GPL on mechanical properties, thermal conductivity and electrical resistivity of the B4 C ceramics were investigated. Mechanical properties ran up to optimal condition with hardness of 29.1 GPa, bending strength of 383.9 GPa and fracture toughness of 5.72 MPa m1/2 with 0.8 wt% GPL separately. Thermal conductivity and electrical resistivity reached extreme values of 26...
April 2018: Royal Society Open Science
Zhen Yin, Ahmad Dastjerdi, Francois Barthelat
Glasses are optically transparent, hard materials that have been in sustained demand and usage in architectural windows, optical devices, electronics and solar panels. Despite their outstanding optical qualities and durability, their brittleness and low resistance to impact still limits wider applications. Here we present new laminated glass designs that contain toughening cross-ply architectures inspired from fish scales and arthropod cuticles. This seemingly minor enrichment completely transforms the way laminated glass deforms and fractures, and it turns a traditionally brittle material into a stretchy and tough material with little impact on surface hardness and optical quality...
May 10, 2018: Acta Biomaterialia
Zhihui Zhang, Lan Zhang, Zhenglei Yu, Jingjing Liu, Xiujuan Li, Yunhong Liang
In natural biological systems, many insects in complex environments exhibit exemplary mechanical properties. Dragonfly wings are light and strong enough to withstand wind loading. Their rigid veins play supporting and strengthening roles to enhance resistance to fatigue. To explore the effect of veins on arresting cracking in the wing, the costa, subcosta, radius R1, and two areas of dragonfly hind wings were samples for in situ tensile tests. The fracture process of the samples was observed with a high-speed camera and a scanning electron microscope...
May 5, 2018: Micron: the International Research and Review Journal for Microscopy
Weiyan Li, Jian Sun
BACKGROUND Polymer-infiltrated ceramic-network (PICN) dental material is a new and practical development in orthodontics. Sintering is the process of forming a stable solid mass from a powder by heating without melting. The aim of this study was to evaluate the effects of sintering temperature on the mechanical properties of a PICN zirconia dental material. MATERIAL AND METHODS A dense zirconia ceramic and four PICN zirconia dental materials, with varying porosities, were sintered at three different temperatures; 12 PICN zirconia dental materials based on these porous ceramics were prepared, as well as a pure polymer...
May 10, 2018: Medical Science Monitor: International Medical Journal of Experimental and Clinical Research
Ming Li, Pan Xiong, Feng Yan, Sijie Li, Changhong Ren, Zhichen Yin, Ang Li, Huafang Li, Xunming Ji, Yufeng Zheng, Yan Cheng
Hydroxyapatite (HA) is an attractive bioceramic for hard tissue repair and regeneration due to its physicochemical similarities to natural apatite. However, its low fracture toughness, poor tensile strength and weak wear resistance become major obstacles for potential clinical applications. One promising method to tackle with these problems is exploiting graphene and its derivatives (graphene oxide and reduced graphene oxide) as nanoscale reinforcement fillers to fabricate graphene-based hydroxyapatite composites in the form of powders, coatings and scaffolds...
March 2018: Bioactive Materials
Y X Wang, Xiaoke Lu, Tianyuan Xin, Qiang Zhang, Qiu Xu, Tianhao Wei
Recently, a series of graphene-like binary monolayers (g-SiCx), where Si partly substitutes the C positions in graphene, have been obtained by tailoring the bandgaps of graphene and silicene that has made them a promising material for application in opto-electronic devices. Subsequently, evaluating the mechanical properties of g-SiCx has assumed great importance for engineering applications. In this study, we quantified the in-plane mechanical properties of g-SiCx (x = 7, 5, 3, 2 and 1) monolayers (also including graphene and silicone) based on density function theory (DFT)...
May 9, 2018: Nanotechnology
Chunyang Wang, Jia Xu, Gen Wen, Yimin Chai
One-stage reconstruction of composite bone and soft-tissue defects in the forearm remains a tough challenge. Here, we present a case of reconstruction of complex tissue defect at forearm with a chimeric flap consisting of a sural neurocutaneous flap and a fibular graft. A 61-year-old man suffered from a machine crush injury in his left forearm, resulting in a complex tissue defect including extensive dorsomedial soft-tissue, digit extensor muscles of 2-4 fingers, the muscle flexor carpi ulnaris, the ulna bone with 5...
May 7, 2018: Microsurgery
Renata A Esteves, Letícia C C Boaro, Flávia Gonçalves, Luiza M P Campos, Cecy M Silva, Leonardo Eloy Rodrigues-Filho
This study evaluated the influence of formulation and thermal treatment on the degree of conversion, fracture toughness, flexural strength, and elastic modulus of experimental composites. Six composites were analyzed at BisGMA : TEGDMA molar ratios of 1 : 1 and 7 : 3 with filler at 30, 50, and 70 wt%. The degree of conversion was analyzed by Fourier transform infrared spectroscopy, fracture toughness was measured using the single-edge notched beam, and flexural strength and elastic modulus were measured with the 3-point bend test...
2018: BioMed Research International
Rémy Gauthier, Hélène Follet, Max Langer, Evelyne Gineyts, Frédéric Rongiéras, Françoise Peyrin, David Mitton
Human cortical bone fracture processes depend on the internal porosity network down to the lacunar length scale. Recent results show that at the collagen scale, the maturation of collagen cross-links may have a negative influence on bone mechanical behavior. While the effect of pentosidine on human cortical bone toughness has been studied, the influence of mature and immature enzymatic cross-links has only been studied in relation to strength and work of fracture. Moreover, these relationships have not been studied on different paired anatomical locations...
May 3, 2018: Bone
Joseph E Pichamuthu, Spandan Maiti, Maria G Gan, Nicole M Verdecchia, Steven L Orebaugh, David A Vorp
Nerve blocks are frequently performed by anesthesiologists to control pain. For sciatic nerve blocks, the optimal placement of the needle tip between its paraneural sheath and epineurial covering is challenging, even under ultrasound guidance, and frequently results in nerve puncture. We performed needle penetration tests on cadaveric isolated paraneural sheath (IPS), isolated nerve (IN), and the nerve with overlying paraneural sheath (NPS), and quantified puncture force requirement and fracture toughness of these specimens to assess their role in determining the clinical risk of nerve puncture...
April 25, 2018: Journal of Biomechanics
Bo Pang, Yunsheng Zhang, Guojian Liu
Nowadays, numerous concrete structures are urgently needed to be repaired and strengthened due to the severe safety and durability. In this study, a novel type of silane-based interfacial coupling agent (ICA) is prepared by modifying silane coupling agent (SCA) with hydrothermally treated nano-silica (HTNS). The effect of ICA on the cement hydration and crystalline form as well as the hydrolysis/condensation extent of siloxanes is illustrated. The bonding strength, morphology and propagation of the interface cracks, and the interfacial ductile fracture characterization are investigated...
May 4, 2018: ACS Applied Materials & Interfaces
Reese Jones, Jessica M Rimsza, Louise J Criscenti
Using an atomistic technique consistent with continuum balance laws and drawing on classical fracture mechanics theory, we estimate the resistance to fracture propa- gation of amorphous silica. We discuss correspondence and deviations from classical linear elastic fracture mechanics theory including size dependence, rigid/floppy modes of deformation, and the effects of surface energy and stress.
May 4, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Sahar Abdulrazzaq Naji, Marjan Behroozibakhsh, Tahereh Sadat Jafarzadeh Kashi, Hossein Eslami, Reza Masaeli, Hosseinali Mahgoli, Mohammadreza Tahriri, Mehrsima Ghavvami Lahiji, Vahid Rakhshan
PURPOSE: The aim of this preliminary study was to investigate, for the first time, the effects of addition of titania nanotubes (n-TiO2 ) to poly methyl methacrylate (PMMA) on mechanical properties of PMMA denture base. MATERIALS AND METHODS: TiO2 nanotubes were prepared using alkaline hydrothermal process. Obtained nanotubes were assessed using FESEM-EDX, XRD, and FT-IR. For 3 experiments of this study (fracture toughness, three-point bending flexural strength, and Vickers microhardness), 135 specimens were prepared according to ISO 20795-1:2013 (n of each experiment=45)...
April 2018: Journal of Advanced Prosthodontics
Qian Zhao, Yunhong Liang, Qingping Liu, Zhihui Zhang, Zhenglei Yu, Luquan Ren
Based on microstructure characteristics of Meretrix lusoria shell and Rapana venosa shell, bionic coupling layered B₄C/5083Al composites with different layered structures and hard/soft combination models were fabricated via hot pressed sintering. The simplified bionic coupling models with hard and soft layers were similar to layered structure and hardness tendency of shells, guiding the bionic design and fabrication. B₄C/5083Al composites with various B₄C contents and pure 5083Al were treated as hard and soft layers, respectively...
April 26, 2018: Materials
Shruti Rattan, Linqing Li, Hang Kuen Lau, Alfred J Crosby, Kristi L Kiick
Detailed understanding of the local structure-property relationships in soft biopolymeric hydrogels can be instrumental for applications in regenerative tissue engineering. Resilin-like polypeptide (RLP) hydrogels have been previously demonstrated as useful biomaterials with a unique combination of low elastic moduli, excellent resilience, and cell-adhesive properties. However, comprehensive mechanical characterization of RLP hydrogels under both low-strain and high-strain conditions has not yet been conducted, despite the unique information such measurements can provide about the local structure and macromolecular behavior underpinning mechanical properties...
April 27, 2018: Soft Matter
Enrui Zhang, Ruobing Bai, Xavier P Morelle, Zhigang Suo
Polyacrylamide hydrogels are highly stretchable and nearly elastic. Their stress-stretch curves exhibit small hysteresis, and change negligibly after many loading cycles. Polyacrylamide is used extensively in applications, and is the primary network for many types of tough hydrogels. Recent experiments have shown that polyacrylamide hydrogels are susceptible to fatigue fracture, but available data are limited. Here we study fatigue fracture of polyacrylamide hydrogels of various water contents. We form polymer networks in all samples under the same conditions, and then obtain hydrogels of 96, 87, 78, and 69 wt% of water by solvent exchange...
April 23, 2018: Soft Matter
Navid Kazem, Michael D Bartlett, Carmel Majidi
Soft and tough materials are critical for engineering applications in medical devices, stretchable and wearable electronics, and soft robotics. Toughness in synthetic materials is mostly accomplished by increasing energy dissipation near the crack tip with various energy dissipation techniques. However, bio-materials exhibit extreme toughness by combining multi-scale energy dissipation with the ability to deflect and blunt an advancing crack tip. Here, we demonstrate a synthetic materials architecture that also exhibits multi-modal toughening, whereby embedding a suspension of micron sized and highly deformable liquid metal (LM) droplets inside a soft elastomer, the fracture energy dramatically increases by up to 50x (from 250 ± 50 J m-2 to 11,900 ± 2600 J m-2 ) over an unfilled polymer...
April 16, 2018: Advanced Materials
Tyler R Long, Robert M Elder, Erich D Bain, Kevin A Masser, Timothy W Sirk, Jian H Yu, Daniel B Knorr, Joseph L Lenhart
The apparent molecular weight between crosslinks (Mc,a) in a polymer network plays a fundamental role in the network mechanical response. We systematically varied Mc,a independent of strong noncovalent bonding by using ring-opening metathesis polymerization (ROMP) to co-polymerize dicyclopentadiene (DCPD) with a chain extender that increases Mc,a or a di-functional crosslinker that decreases Mc,a. We compared the ROMP series quasi-static modulus (E), tensile yield stress (σy), and fracture toughness (KIC and GIC) in the glassy regime with literature data for more polar thermosets...
April 16, 2018: Soft Matter
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