Hierarchical Structure of a Natural Composite: Insect Cuticle

1991 ◽  
Vol 255 ◽  
Author(s):  
Stephen L. Gunderson ◽  
Katie E. Gunnison ◽  
John W. Sawvel
Keyword(s):  
Load Transfer ◽  
Natural Fiber ◽  
Polymeric Composite ◽  
Shear Stiffness ◽  
Insect Cuticle ◽  
Protein Matrix ◽  
Crosslinking Process ◽  
The Matrix ◽  
Improved Performance ◽  
Strength And Stiffness

AbstractThe insect cuticle is an excellent example of a natural, fiber-reinforced, polymeric composite consisting of chitin fibers embedded in a protein matrix. Optical and electron microscopy have been used to examine the structure and interaction of the constituents of the bessbeetle (Odontotaenius disjunctus) cuticle from the molecular to the macroscopic levels.Molecular chains of the polysaccharide chitin (N-acetylglucosamine) are grouped together to form “fibrils” which are either dispersed throughout the matrix or combined to form larger “fibers”. The fibers are unidirectionally oriented within individual sheets or laminae which are stacked on top of one another at various angles forming a laminated structure.The protein matrix is ductile upon initial deposition but then undergoes a crosslinking process which increases its shear stiffness, thereby improving load transfer between fibers. The matrix is bound to the chitin via beta linkages holding it together at both the fibril and fiber levels. The matrix has a fibrous morphology which provides adequate toughness in spite of the high degree of crosslinking.Reference is made to designs observed in the bessbeetle cuticle which could be applied to man-made composites for improved performance primarily in the areas of damage tolerance and strength and stiffness coupled with low weight. For these designs to be implemented using synthetic materials, new or modified processing and fabrication methods are needed.

Investigation on Impact and Compression Properties of Pineapple Reinforced Polymer Composite

2014 ◽  
Vol 591 ◽  
pp. 116-119 ◽  
Author(s):  
V.M. Manickavasagam ◽  
B. Vijaya Ramnath ◽  
C. Elanchezhian ◽  
J. Jenish ◽  
S. Jayavel ◽  
...  
Keyword(s):  
Load Transfer ◽  
Natural Fiber ◽  
Fiber Composite ◽  
Mechanical Efficiency ◽  
Continuous Phase ◽  
Compression Properties ◽  
Surrounding Matrix ◽  
Reinforced Composite ◽  
Load Carrying ◽  
The Matrix

The Natural fiber composites form a combination of plant derived fibers with plastic binders (Polymer matrices). The fibers form the fillers or reinforcements of the composite and the matrix is the continuous phase. In general, fibers are principal load carrying members while the surrounding matrix keeps them in the desired position, acts as a load transfer medium between them. So fibers with good strength and modulus and having good bonding with matrix should be used to a produce a good quality composite material [1-3]. The mechanical efficiency of a fiber composite depends on the adhesion between the matrix and the reinforcement [4-7]. This paper is to evaluate impact and compression properties of pineapple fiber based reinforced composite with epoxy resin as matrix.

Critical Fiber Length for Load Transfer in Carbon Nanotube (CNT) Reinforced Composites

Aerospace ◽  
2004 ◽  
Author(s):  
Feridun Delale ◽  
Huapei Wan
Keyword(s):  
Carbon Nanotube ◽  
Polymer Matrix ◽  
Fiber Length ◽  
Strain Energy ◽  
Load Transfer ◽  
Effective Properties ◽  
Critical Length ◽  
Polymeric Composite ◽  
Effective Moduli ◽  
The Matrix

In this paper the load transfer mechanism in a carbon nanotube (CNT) reinforced polymeric composite is considered. It is assumed that the polymer matrix is reinforced with single-walled carbon nanotubes and that the continuum model with adjustments is valid in estimating the effective properties of the composite. The existing studies contradict each other with respect to effective load transfer between the matrix and the nanotubes. In this study we show that there is a critical CNT length below which the load transfer is not effective. Thus for an effective load transfer the CNT length must exceed a critical length. To determine the critical length we consider a CNT embedded in a polymer matrix. The polymer/CNT interface is modeled as a distinct layer with elastic properties different than those of the CNT and the matrix. The strain energy change due to the inclusion of a CNT in a polymer matrix is then computed for various interphase stiffnesses using the finite element method. The variation of the strain energy per unit fiber length ΔU/L is plotted versus the aspect ratio of the CNT, L/D. It is observed that ΔU/L first increases steeply with L/D and then reaches a plateau. Since the region of constant ΔU/L is associated with uniform stress distribution, we define the critical CNT length as 90% of the asymptotic value of ΔU/L. It is shown that the load transfer is affected by the nature of the interphase. Next, using a dilute solution the effective moduli of the composite are derived for the cases of both hard and soft interphase. The results indicate that the nature of matrix/CNT interface affects the effective moduli of the composite only slightly.

Preparation of Electron Transparent Metal-Matrix Composites

1968 ◽  
Vol 26 ◽  
pp. 334-335 ◽  
Author(s):  
M. R. Pinnel ◽  
A. Lawley
Keyword(s):  
Stainless Steel ◽  
Load Transfer ◽  
Volume Fraction ◽  
Steel Wire ◽  
Initial Step ◽  
Interfacial Region ◽  
Matrix Composites ◽  
Specific Test ◽  
The Matrix ◽  
The One

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.

Deformation at interfaces of Ti-6Al-4V/SiC fiber composites

1992 ◽  
Vol 50 (1) ◽  
pp. 158-159
Author(s):  
Warren J. Moberly ◽  
Daniel B. Miracle ◽  
S. Krishnamurthy
Keyword(s):  
Thermal Stresses ◽  
Load Transfer ◽  
Coefficient Of Thermal Expansion ◽  
Hot Isostatic Pressing ◽  
Matrix Composites ◽  
Ongoing Research ◽  
Aerospace Applications ◽  
Sic Fiber ◽  
The Matrix ◽  
Intermetallic Matrix Composites

Titanium-aluminum alloy metal matrix composites (MMC) and Ti-Al intermetallic matrix composites (IMC), reinforced with continuous SCS6 SiC fibers are leading candidates for high temperature aerospace applications such as the National Aerospace Plane (NASP). The nature of deformation at fiber / matrix interfaces is characterized in this ongoing research. One major concern is the mismatch in coefficient of thermal expansion (CTE) between the Ti-based matrix and the SiC fiber. This can lead to thermal stresses upon cooling down from the temperature incurred during hot isostatic pressing (HIP), which are sufficient to cause yielding in the matrix, and/or lead to fatigue from the thermal cycling that will be incurred during application, A second concern is the load transfer, from fiber to matrix, that is required if/when fiber fracture occurs. In both cases the stresses in the matrix are most severe at the interlace.

Green composites and their contribution toward sustainability: A review

2021 ◽  
pp. 096739112110093
Author(s):  
Edgar Vázquez-Núñez ◽  
Andrea M Avecilla-Ramírez ◽  
Berenice Vergara-Porras ◽  
María del Rocío López-Cuellar
Keyword(s):  
Natural Fiber ◽  
World Market ◽  
Raw Material ◽  
Green Composites ◽  
Green Materials ◽  
Global Problems ◽  
The Matrix ◽  
Green Economies ◽  
Green Polymer ◽  
World Environment

The current world environment scenario demands new and more eco-friendly solutions to global problems that cover the demands for materials. This sector has included green polymer-based composites and natural reinforcers from origins of renewable sources, these Green Composites (GC), natural-fiber-reinforced bio-composites in which the matrix is a bio-based polymer, have shown attractive characteristics. Biodegradability is one of the most important attributes for these new “green” materials, in that this characteristic allows for their introduction into the world market as an environmental solution. The manufacturing processes for obtaining these materials have observed important improvements because each raw material exhibits different properties and characteristics and their eco-friendly character has facilitated its incorporation into diverse sectors, such as construction, automotive, packaging, and medicine, among others. At present, this segment represents an important income for some economies, especially those where these resources are available, enhancing the creation of green economies, strengthening the world’s efforts toward sustainability.

Structure, Mechanics and Failure of Stochastic Fibrous Networks: Part I—Microscale Considerations

2000 ◽  
Vol 122 (4) ◽  
pp. 450-459 ◽  
Author(s):  
C. W. Wang ◽  
L. Berhan ◽  
A. M. Sastry
Keyword(s):  
Load Transfer ◽  
Nonlinear Behavior ◽  
Polymeric Composite ◽  
Cost Effective ◽  
Failure Criteria ◽  
Zone Model ◽  
Fibrous Materials ◽  
Linear Solution ◽  
Model Complex ◽  
Computationally Intensive

Applications for porous fibrous materials range from electrochemical substrates to web reinforcement in polymeric composite materials. The details of local load transfer are studied in a class of cost-effective, stochastic fibrous networks used in battery applications, which form the substrate for a composite electrode. The connectivity of these materials is quantitatively related to modulus and strength, and detailed results of different simulations approaches in approximating material construction are discussed. In Part I, we discuss microscale assumptions, including beam type, nodal connections and equivalence of models to more physically realistic models. Simulation of large networks is computationally intensive, and show low-strain, nonlinear behavior even when comprised of elastic elements when failure criteria (here, strength-of-materials) are applied to produce sequential rupture of beams and nodes. Strategies for effective simulation of these materials requires detailed analysis of the simplest assumptions which can be made at the microscale which produce acceptably realistic response. We show that simple Euler-Bernoulli beam elements can be used to effectively model such materials, even when segment lengths in a network are very small. Moreover, connections comprised of simple torsion springs produce realistic behavior, and can mimic more realistic junctures by adaptation of the linear solution to a compliant zone model. In Part II of this work, we demonstrate the effect of model selection on full network behavior, and also discuss issues of connectivity at the scale of the porous material rather than element-by-element. This work points toward use of simple constructions to model complex behavior, and may ultimately provide insight into modeling of a large class of porous materials. [S0094-4289(00)01704-7]

Lateral Load Performance of Panelized Wood I-Joist Floor Systems

2020 ◽  
Vol 70 (4) ◽  
pp. 428-438
Author(s):  
Sigong Zhang ◽  
Ying Hei Chui ◽  
David Joo
Keyword(s):  
Load Transfer ◽  
Mechanical Performance ◽  
Small Scale ◽  
Construction Time ◽  
Plane Shear ◽  
Floor Systems ◽  
Diaphragm Action ◽  
Wood Frame ◽  
Strength And Stiffness ◽  
Frame Construction

Abstract Panelized light wood frame construction is becoming more popular due to the faster construction time and shortage of onsite skilled labor. To use light wood frame panels effectively in panelized floor systems, panel-to-panel joints must be fastened adequately to allow load transfer between panels. They must also possess in-plane shear strength and stiffness comparable to stick-built, staggered-sheathed assemblies. This study was designed to develop efficient and effective panel-to-panel joints for connecting adjacent floor panels built with wood I-joists and evaluate the efficiency of the joints in achieving diaphragm action. At first, a number of these panel-to-panel joints were tested in the laboratory using a small-scale diaphragm test setup to determine their efficiency in transferring in-plane forces between panels. Test results showed that a small decrease in in-plane stiffness was expected for the most effective joints, but their strengths were significantly higher than at the same location in a conventional site-built floor diaphragm. The presence of blockings and use of two-row nailing were found to considerably improve stiffness and strength. These features can be used to mitigate the potential reduction in mechanical performance of panelized floor construction, in comparison with the site-built wood I-joist floor.

STRUCTURING OF CURED POLYMERIC COMPOSITE MATERIALS IN A MICROWAVE ELECTROMAGNETIC FIELD

2021 ◽  
pp. 3-9
Author(s):  
I. V. Zlobina
Keyword(s):  
Electromagnetic Field ◽  
Composite Materials ◽  
Polymer Composite ◽  
Contact Interaction ◽  
Energy Systems ◽  
Polymeric Composite ◽  
Strength Characteristics ◽  
Polymer Composite Materials ◽  
Reinforcing Fibers ◽  
The Matrix

Based on studies of the microstructure of the matrix of cured polymer composite materials and the area of its contact interaction with reinforcing fibers, the hypothesis of its structuring in the microwave electromagnetic field with an increase in the contact interaction surfaces due to an increase in the number of agglomerates with small transverse dimensions and a decrease in porosity in the macro- and mesopore regions is substantiated. These effects can be used as a basis for increasing the strength characteristics and uniformity of their values after exposure to a microwave electromagnetic field. The results of this work can be used in the development of technologies for finishing hardening of products made of carbon and fiberglass for various transport and energy systems.

Enhancement of Mechanical Properties by Reinforcing Magnesium With Ni-Coated Carbon Nanotubes

2010 ◽  
Author(s):  
M. H. Nai ◽  
C. S. Goh ◽  
S. M. L. Nai ◽  
J. Wei ◽  
M. Gupta
Keyword(s):  
Carbon Nanotubes ◽  
Load Transfer ◽  
Matrix Material ◽  
Strength Based ◽  
The Matrix ◽  
Rapid Sintering ◽  
Reinforcing Material ◽  
Coated Carbon ◽  
Strength And Ductility ◽  
Walled Cnts

In this study, carbon nanotubes (CNTs) are coated with nickel (Ni) to improve the wettability of the CNT surface and metal matrix, and allow an effective load transfer from the matrix to nanotubes. Pure magnesium is used as the matrix material and different weight percentages of Ni-coated multi-walled CNTs are incorporated as the reinforcing material. The nanocomposite materials are synthesized using the powder metallurgy route followed by microwave assisted rapid sintering. Mechanical property characterizations reveal an improvement of 0.2% yield strength, ultimate tensile strength and ductility with the addition of Ni-CNTs. As such, Ni-coated CNTs can be used as a reinforcement in magnesium to improve the formability of the material for light-weight, strength-based applications.

scholarly journals Biomimetic Composites with Enhanced Toughening Using Silk Inspired Triblock Proteins and Aligned Nanocellulose Reinforcements

2019 ◽  
Author(s):  
Pezhman Mohammadi ◽  
A. Sesilja Aranko ◽  
Christopher P. Landowski ◽  
Olli Ikkala ◽  
Kristaps Jaudzems ◽  
...  
Keyword(s):  
Spider Silk ◽  
Cellulose Nanofibrils ◽  
High Strength ◽  
Beta Sheets ◽  
Conformational Switching ◽  
Multiple Length Scales ◽  
The Matrix ◽  
Strength And Stiffness ◽  
Flow Alignment

Silk and cellulose are biopolymers that show a high potential as future sustainable materials.They also have complementary properties, suitable for combination in composite materials where cellulose would form the reinforcing component and silk the tough matrix. Therein, a major challenge concerns balancing structure and properties in the assembly process. We used recombinant proteins with triblock architecture combining structurally modified spider silk with terminal cellulose affinity modules. Flow-alignment of cellulose nanofibrils and triblock protein allowed a continuous fiber production.The protein assembly involved phase separation into concentrated coacervates, with subsequent conformational switching from disordered structures to beta sheets. This gave the matrix a tough adhesiveness, forming a new composite material with high strength and stiffness combined with increased toughness. We show that versatile design possibilities in protein engineering enable new fully biological materials, and emphasize the key role of controlled assembly at multiple length scales for realization.<br>

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