scholarly journals Regulation of hard α-keratin mechanics via control of intermediate filament hydration: matrix squeeze revisited

2013 ◽  
Vol 280 (1750) ◽  
pp. 20122158 ◽  
Author(s):  
Daniel A. Greenberg ◽  
Douglas S. Fudge
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
Critical Role ◽  
Tensile Modulus ◽  
Modulus Ratio ◽  
Swelling Behaviour ◽  
Highly Sensitive ◽  
The Matrix ◽  
High Matrix ◽  
And Function

Mammalian hard α-keratins are fibre-reinforced biomaterials that consist of 10 nm intermediate filaments (IFs) embedded in an elastomeric protein matrix. Recent work suggests that the mechanical properties of IFs are highly sensitive to hydration, whereas hard α-keratins such as wool, hair and nail are relatively hydration insensitive. This raises the question of how mammalian keratins remain stiff in water. The matrix squeeze hypothesis states that the IFs in hard α-keratins are stiffened during an air-drying step during keratinization, and subsequently locked into a dehydrated state via the oxidation and cross-linking of the keratin matrix around them. The result is that even when hard α-keratins are immersed in water, their constituent IFs remain essentially ‘dry’ and therefore stiff. This hypothesis makes several predictions about the effects of matrix abundance and function on hard α-keratin mechanics and swelling behaviour. Specifically, it predicts that high matrix keratins in water will swell less, and have a higher tensile modulus, a higher yield stress and a lower dry-to-wet modulus ratio. It also predicts that disruption of the keratin matrix in water should lead to additional swelling, and a drop in modulus and yield stress. Our results are consistent with these predictions and suggest that the keratin matrix plays a critical role in governing the mechanical properties of mammalian keratins via control of IF hydration.

Wear Resistance and Mechanical Properties of Polymeric Fibers Filled with Inorganic Fillers

2006 ◽  
Vol 977 ◽  
Author(s):  
Toshihira Irisawa ◽  
Masatoshi Shioya ◽  
Haruki Kobayashi ◽  
Junichi Kaneko
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Tensile Modulus ◽  
Nylon 6 ◽  
Polymeric Fibers ◽  
Poly Ethylene Terephthalate ◽  
The Matrix ◽  
Pet Fibers ◽  
Inorganic Fillers ◽  
Poly Ethylene

AbstractThe wear resistance and the mechanical properties of polymer matrix composite fibers filled with inorganic fillers have been investigated in order to find out the way to increase the wear resistance of the fibers without losing tensile modulus and strength. Nylon 6 and poly(ethylene terephthalate) have been used as the matrix polymer and aluminum borate whisker and carbon nanotube have been used as the fillers. The wear resistance of the fibers has been evaluated by observing the fiber cross section after the side of the fiber was worn using a rotating drum covered with abrasive paper. The wear resistance of the nylon 6 and PET fibers was increased by the addition of these fillers without the loss of tensile modulus and strength. The effects of the addition of the fillers on the wear resistance have been compared with the effects of stretching and heat treatment of the fibers.

Mechanical Properties of Biomimetic Leaf Composite

2016 ◽  
Author(s):  
Hamid Nayeb Hashemi ◽  
Gongdai Liu ◽  
Ashkan Vaziri ◽  
Masoud Olia ◽  
Ranajay Ghosh
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
Poisson’S Ratio ◽  
Composite Structures ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Poisson's Ratio ◽  
Closed Cell ◽  
Cell Architecture ◽  
The Matrix

In this paper, we mimic the venous morphology of a typical plant leaf into a fiber composite structure where the veins are replaced by stiff fibers and the rest of the leaf is idealized as an elastic perfectly plastic polymeric matrix. The variegated venations found in nature are idealized into three principal fibers — the central mid-fiber corresponding to the mid-rib, straight parallel secondary fibers attached to the mid-fiber representing the secondary veins and then another set of parallel fibers emanating from the secondary fibers mimicking the tertiary veins of a typical leaf. The tertiary fibers do not interconnect the secondary fibers in our present study. We carry out finite element (FE) based computational investigation of the mechanical properties such as Young’s moduli, Poisson’s ratio and yield stress under uniaxial loading of the resultant composite structures and study the effect of different fiber architectures. To this end, we use two broad types of architectures both having similar central main fiber but differing in either having only secondary fibers or additional tertiary fibers. The fiber and matrix volume fractions are kept constant and a comparative parametric study is carried out by varying the inclination of the secondary fibers. We find significant effect of fiber inclination on the overall mechanical properties of the composites with higher fiber angles transitioning the composite increasingly into a matrix-dominated response. We also find that in general, composites with only secondary fibers are stiffer with closed cell architecture of the secondary fibers. The closed cell architecture also arrested the yield stress decrease and Poisson’s ratio increase at higher fiber angles thereby mitigating the transition into the matrix dominated mode. The addition of tertiary fibers also had a pronounced effect in arresting this transition into the matrix dominated mode. However, it was found that indiscriminate addition of tertiary fibers may not provide desired additional stiffness for fixed volume fraction of constituents. In conclusion, introducing a leaf-mimicking topology in fiber architecture can provide significant additional degrees of tunability in design of these composite structures.

Nano-dispersed Particulate Ceramics in Poly-Lactide-Co-Glycolide Composites Improve Implantable Bone Substitute Properties

2007 ◽  
Vol 1056 ◽  
Author(s):  
Huinan Liu ◽  
Thomas J. Webster
Keyword(s):  
Mechanical Properties ◽  
Large Fraction ◽  
Critical Role ◽  
Tensile Modulus ◽  
Nano Particles ◽  
Loading Conditions ◽  
Ceramic Phase ◽  
Natural Bone ◽  
Physiological Loading ◽  
Orthopedic Applications

ABSTRACTMetallic materials widely used in orthopedic applications have much stronger mechanical properties (such as elastic modulus) than natural bone, which can weaken the newly formed bone interface due to stress-shielding. Because natural bone is under continuous physiological stresses (such as compression, tension, torsion, and/or bending), the mechanical properties of orthopedic implant materials should closely match those of living bone. This is necessary to minimize stress and strain imbalances during physiological loading conditions which will lead to implant failure. The objective of the present study was to characterize the mechanical properties of PLGA with well-dispersed nanophase titania. The dispersion of titania in PLGA was controlled by sonication and was characterized by field emission scanning electron microscopy and image analysis. For this purpose, two major stresses (compression and tension) that natural bone experiences under physiological loading conditions were characterized using an Instron Material Testing System. The results showed that nano-dispersed titania particles in PLGA increased the compressive and tensile modulus of such scaffolds compared to pure PLGA scaffolds and the more agglomerated ceramics in PLGA scaffolds. The mechanisms behind these results were also speculated. Since the predominant feature of nano-particles lies in their ultra-fine dimension, a large fraction of filler atoms can reside at the PLGA-ceramic interface which can lead to a stronger interfacial interaction, but only if the nano-particles are well dispersed at the nanometer level in the surrounding polymer matrix. As the interfacial PLGA-ceramic structure plays a critical role in determining the mechanical properties of composites, nano-composites with a great number of smaller interfaces could be expected to provide unusual properties, and the shortcomings induced by the heterogeneity of conventional (or micron) particle filled composites would also be avoided. Therefore, coupled with prior studies demonstrating greater osteoblast functions, the combination of PLGA with a strong and biocompatible well-dispersed nano-ceramic phase may provide better candidate materials for orthopedic applications.

Mechanical properties of unidirectional aligned bagasse fibers/vinyl ester composite

2016 ◽  
Vol 36 (2) ◽  
pp. 157-163 ◽  
Author(s):  
Ayyanar Athijayamani ◽  
Balasubramaniam Stalin ◽  
Susaiyappan Sidhardhan ◽  
Azeez Batcha Alavudeen
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Impact Strength ◽  
Vinyl Ester ◽  
Flexural Modulus ◽  
Tensile Modulus ◽  
Short Beam ◽  
Beam Shear ◽  
The Matrix ◽  
The Impact

Abstract The present study describes the preparation of aligned unidirectional bagasse fiber-reinforced vinyl ester (BFRVE) composites and their mechanical properties such as tensile, flexural, shear and impact strength. Composites were prepared by a hand lay-up technique developed in our laboratory with the help of a hot press. Mechanical properties were obtained for different fiber contents by varying the number of layers. The obtained tensile property values were compared with the theoretical results. The results show that the tensile strength increased linearly up to 44 wt% and then dropped. However, the tensile modulus increased linearly from 17 wt% to 60 wt%. In the case of flexural properties, the flexural strength increased up to 53 wt% and started to decrease. However, the flexural modulus also increased linearly up to 60 wt%. The impact strength values were higher than the matrix materials for all the specimens. The short beam shear strength values were also increased up to 53 wt% and then dropped. The modified Bowyer and Bader (MBB) model followed by the Hirsch model shows a very good agreement with experimental results in both tensile strength and modulus.

Interfacial Effect on Mechanical Properties of Polypropylene Ternary Nanocomposites

2018 ◽  
Vol 913 ◽  
pp. 564-570 ◽  
Author(s):  
Wei Wang ◽  
Wei Wang ◽  
Dong Lv ◽  
Jing Shen Wu
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Vital Role ◽  
Enhancement Effect ◽  
Weak Interface ◽  
The Matrix ◽  
Grafted Nanoparticles ◽  
The Impact

The matrix/filler interface plays a vital role in mechanical properties of polypropylene (PP)/rigid nanoparticles composites. In general, the use of spherical stearic acid modified CaCO3 (SA-CaCO3) can induce a weak interfacewhich facilitatesparticle debonding from the matrix under loading and reduces plastic resistance, enhancing the toughness of nanocomposites, while the use of polymer-grafted nanoparticles (PGS) can improve the Young’s modulus and yield stress because of strong interfacial binding between particle and matrix. With the objective to simultaneously improve the modulus, yield stress and toughness, the ternary nanocomposites, PP/PGS/CaCO3 (PPSC), were prepared and the morphology, crystallization, and mechanical behavior were investigated and compared to their binary nanocomposites. The results show that Young’s modulus is enhanced as the particle loading, and the yield stress is balanced by two interactions, i.e. the decreasing effect of the weak interface and the enhancement effect of the strong interface. The impact strength of the ternary nanocomposites shows insignificant improvement compared with neat PP, which is attributed to the brittle effect of the weak interface in the particle cluster of SA-CaCO3 and PGS.

Mechanical Properties of Bamboo Charcoal (BC)/Poly(Lactic) Acid (PLA) Composites

2019 ◽  
Vol 801 ◽  
pp. 121-126
Author(s):  
Rapeeporn Srisuk ◽  
Laongdaw Techawinyutham ◽  
Wantana Koetniyom ◽  
Rapeephun Dangtungee
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Lactic Acid ◽  
Shear Viscosity ◽  
Tensile Modulus ◽  
Poly Lactic Acid ◽  
Bamboo Charcoal ◽  
Elongation At Break ◽  
The Matrix

The influence of bamboo charcoal (BC) in Poly (lactic) acid (PLA) matrix as masterbatch was studied on mechanical 40:60, 50:50 and 60:40 of masterbatch. BC MBs were diluted at 1 phr, 3 phr, and 5 phr. BC showed even distribution in PLA matrix; however,, it decreased compatibility in the matrix. The infusion of BC in PLA matrix enhanced the tensile modulus; however, there was a reduction in the tensile strength and the elongation at break. It could also be ascertained that there is no signification difference in the hardness of BC/PLA composites compared with neat PLA. The addition of BC slightly decreased shear viscosity of the composites. The optimal BC content in the composites was found to be 2.82wt.% (5 phr 60:40).

Impact and Quasi-Static Mechanical Properties of a Carbon Fiber Reinforced Carbon Nanotube/Epoxy

2012 ◽  
Author(s):  
Mehran Tehrani ◽  
Ayoub Y. Boroujeni ◽  
Timothy B. Hartman ◽  
Thomas P. Haugh ◽  
Scott W. Case ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Fiber ◽  
Tensile Modulus ◽  
Fiber Reinforced ◽  
Reinforced Plastics ◽  
Structural Applications ◽  
The Matrix ◽  
Static Mechanical ◽  
Carbon Fiber Reinforced ◽  
Composite Energy

Carbon fiber reinforced plastics (CFRPs) possess superior in-plane mechanical properties and are widely used in structural applications. Altering the interphase of CFRPs could alleviate the shortcomings of their out-of-plane performance. In this work, the effects of adding multi-walled carbon nanotubes (MWCNTs) to the epoxy matrix of a CFRP are investigated. Two sets of CFRPs with matrices comprising MWCNTs/epoxy and neat epoxy, respectively, were fabricated. The tensile properties of the two systems, namely the stiffness, the ultimate strength, and the strain to failure were evaluated. The results of the tension tests showed slight changes on the on-axis (along the fiber) tensile modulus and strength of the carbon fiber reinforced epoxy/MWCNT compared to composites with no MWCNTs. The addition of MWCNTs to the matrix moderately increased the strain to failure of the composite. Energy absorption capabilities for the two sets of composites under an intermediate impact velocity (100 m.s−1) test were measured. The energy dissipation capacity of the CFRPs incorporating MWCNTs was higher by 17% compared to the reference CFRPs.

scholarly journals Robust Silica-Cellulose Composite Aerogels with a Nanoscale Interpenetrating Network Structure Prepared Using a Streamlined Process

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 807
Author(s):  
Huazheng Sai ◽  
Jing Zhang ◽  
Zhiqiang Jin ◽  
Rui Fu ◽  
Meijuan Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Modulus ◽  
Silica Aerogels ◽  
Preparation Process ◽  
High Tensile Strength ◽  
Interpenetrating Network ◽  
The Matrix ◽  
Supercritical Co2 Drying ◽  
Composite Aerogels ◽  
Cellulose Composite

Silica aerogels can be strengthened by forming a nanoscale interpenetrating network (IPN) comprising a silica gel skeleton and a cellulose nanofiber network. Previous studies have demonstrated the effectiveness of this method for improving the mechanical properties and drying of aerogels. However, the preparation process is generally tedious and time-consuming. This study aims to streamline the preparation process of these composite aerogels. Silica alcosols were directly diffused into cellulose wet gels with loose, web-like microstructures, and an IPN structure was gradually formed by regulating the gelation rate. Supercritical CO2 drying followed to obtain composite aerogels. The mechanical properties were further enhanced by a simple secondary regulation process that increased the quantity of bacterial cellulose (BC) nanofibers per unit volume of the matrix. This led to the production of aerogels with excellent bendability and a high tensile strength. A maximum breaking stress and tensile modulus of 3.06 MPa and 46.07 MPa, respectively, were achieved. This method can be implemented to produce robust and bendable silica-based composite aerogels (CAs).

A study of the mechanical properties and microstructure of fibre-reinforced aluminium alloy

1995 ◽  
Vol 450 (1940) ◽  
pp. 537-552 ◽  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Yield Stress ◽  
Longitudinal Direction ◽  
Peak Hardness ◽  
Fibre Strength ◽  
Unreinforced Alloy ◽  
Reaction Products ◽  
The Matrix ◽  
Fibre Matrix

A well-consolidated composite, consisting of aluminium-magnesium-silicon alloy (6061) and continuous alumina-based fibres, has been fabricated by liquid metal infiltration. No deleterious reaction products were formed at the fibre-matrix interface and, although a small amount of magnesium penetrated outer regions of the fibre, sufficient remained in the matrix to allow precipitation-hardening upon heat treatment. The bond between fibre and matrix is strong, as evidenced by the mechanical properties, which match ‘rule of mixtures’ predictions with a longitudinal Young’s modulus of ~ 130 GPa and transverse value of ~100 GPa. The shear modulus, ~ 25 GPa, is the same as unreinforced alloy, showing that shear is controlled essentially by the matrix. The effect of fibre orientation on Poisson’s ratio is discussed. Composite yield stress differs in longitudinal and transverse directions (55 MPa and 70 MPa, respectively) due to anisotropic residual stresses in the matrix. Strength in the longitudinal direction is 245 MPa, indicative that fibre strength is reduced during composite manufacture, while transverse strength matches that of unreinforced alloy (170 MPa), as expected with a strong fibre-matrix bond. Heat treatment to matrix peak-hardness increases yield stress and strength but leads to some reduction in ductility.

EFFECTS OF SURFACE TREATMENTS AND SILICA SIZE ON MECHANICAL PROPERTIES OF SILICA-REINFORCED ELASTOMERIC COMPOSITES

2014 ◽  
Vol 87 (2) ◽  
pp. 264-275 ◽  
Author(s):  
Sang-Ryeoul Ryu ◽  
Jun-Man Lee ◽  
Dong-Joo Lee
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Filler Particle ◽  
Tensile Modulus ◽  
Surface Treatments ◽  
Reinforced Composites ◽  
Filler Particle Size ◽  
The Matrix ◽  
Flame Plasma ◽  
Elastomeric Composites

ABSTRACT The effect of surface treatments with atmospheric pressure flame plasma (APFP) and epoxy silane (ES) was studied experimentally to improve the mechanical properties of silica- (volume 40% and mean diameters of 2.2, 12.4, 26.6, and 110 μm) reinforced elastomeric composites. The tensile strength (TS) of the composites increased significantly with decreasing mean diameter. When the diameter was 2.2 μm, the TS of the composite was approximately 1.4 times higher than that of the matrix (2.52 MPa). In addition, the TS of the silica-reinforced composites treated with APFP and ES was increased by 8.8 to 13.3% and 9.9 to 12.5%, respectively, compared with that of the matrix. A larger particle size generally resulted in better surface treatment effects. When the diameter was 26.6 μm, the tensile modulus (TM) of the composite was increased approximately twofold compared with the matrix (0.88 MPa), and the TM of the silica-reinforced composites treated with APFP and ES was increased by 15.6 to 22.8% and 21.1 to 25.8%, respectively, compared with the matrix. Therefore, the importance of surface treatments increases with increasing filler particle size. A conventional silane-coupling agent treatment has few disadvantages, such as the use of organic solvents. Nevertheless, the APFP treatment is a fast, economic, and eco-friendly method for improving the mechanical properties.

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