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Properties of Polymer/Fiber/Ceramic Composites
Published in Noureddine Ramdani, Polymer and Ceramic Composite Materials, 2019
Carbon fiber–reinforced polymers (CFRPs) still represent the best strength-to-weight ratio of all the known construction composite materials. They are stronger than GF-reinforced plastic, but they are comparatively more expensive. This makes them suitable for wherever high strength-to-weight ratio and rigidity are demanded, such as aerospace, automotive, civil engineering, and sporting goods. Despite their high initial strength-to-weight ratio, CFRP composites are not suitable for some structural applications due to their lack of a fatigue endurance and their weak out-of-plane properties, particularly the delamination resistance. Therefore, when using CFRPs for critical cyclic-loading applications, engineers may need to include more strength safety margins to ensure suitable component reliability over a sufficiently long service life. One potential strategy to overcome this problem is the incorporation of micro- and nanoscale inorganic reinforcements, such as carbon nanotube, graphene, clays, and ceramic to these laminated composites [38].
Elastic Stress–Strain Relations
Published in Abdel-Rahman Ragab, Salah Eldin Bayoumi, Engineering Solid Mechanics, 2018
Abdel-Rahman Ragab, Salah Eldin Bayoumi
Composites represent a group of synthesized combinations of materials possessing specific properties that cannot be met by one single material. Such materials have wide engineering applications; for example, several structural and machine elements are made of composites, where high strength and rigidity at low weight are needed, such as in the aerospace and transportation industries. The mechanical properties of composites depend upon the individual mechanical properties of the constituent materials, their volume fraction, distribution, physical and chemical interactions.
Recapitulating Tumor Extracellular Matrix: Design Criteria for Developing Three-Dimensional Tumor Models
Published in Alok Dhawan, Sanjay Singh, Ashutosh Kumar, Rishi Shanker, Nanobiotechnology, 2018
Stiffness, also called rigidity, of the matrix is defined as the amount to which it resists disruption against an applied force. An increase in collagen density and lysyl oxidase mediated cross-linking could be attributed to tissue fibrosis, which results in an elevated level of stiffness. Tumor cells experience this stiffness via mechanotransduction through integrin signaling (Levental et al. 2009). A study has been done in which it was observed that breast and prostate cancer cell lines formed smoother spherical tumoroids compared to those grown on soft matrigel (Bray et al. 2015). The work of Tilghman et al. showed that when cancer cell lines were grown in a collagen-coated matrix with increasing elastic moduli, ranging from 150 to 9600 Pa, nine cell lines revealed a matrix rigidity reliance for growth, growing considerably better on stiff matrices than on soft matrices (Tilghman et al. 2010). Not only that, they showed that cellular adenosine triphosphate (ATP) and protein synthesis including glycolytic enzymes were slower in the cells grown in soft gels. The decrease in metabolic activity led to staying in a dormant stage, and the reverse was observed in stiffer gels, resulting in a more aggressive phenotype (Tilghman et al. 2012). Matrix stiffness could also influence cancer stem cell maintenance; however, the optimum stiffness could depend upon the type of cells (Jabbari et al. 2015). The increase in matrix rigidity disturbs tissue architecture and enhances integrin adhesions that induce focal adhesions and Rho GTPase activity. Rho GTPases are guanosine triphosphate (GTP)-based molecular switches that stimulate actin polymerization as a downstream target. The resultant elevated cytoskeletal tension and focal adhesion formation could eventually stimulate growth factor (GF)-dependent extracellular signal-regulated kinase (ERK) activation that enhances tumor cell growth and progression (see Figure 7.1) (Paszek et al. 2005).
Structural design optimization of a wind turbine blade using the genetic algorithm
Published in Engineering Optimization, 2022
One of the most common goals in designing the wind turbine blade is to minimize its weight. A heavy blade means an increase in the overall hardware weight, which will lead to an increase in the loads, and an increase in production cost. Therefore, an optimized design that maximizes the rigidity while minimizing the weight is sought. In this design optimization process, it is important to select an appropriate optimization algorithm. With respect to the blade design optimization, many existing optimization algorithms have been examined, such as the gradient descent algorithm, momentum algorithm, RMSprop algorithm and dam optimization algorithm. However, these algorithms show limitations in finding the global optimum, depending on the initial estimate of the design variable. This results in extremely long computation time and huge computing expense.
A comparative study of GNPs and MWCNTs additives on dispersion behavior and strength characteristics of the adhesively bonded joints
Published in Journal of Dispersion Science and Technology, 2022
Hassan Ejaz, A. Mubashar, Emad Uddin, Zaib Ali
In recent times, the emphasis on reducing the weight of the structure has become an integral parameter during the design phase of any component or structure. Growing fuel prices, rapid diminishing of fossil fuels, and global environmental impacts are the key parameters that challenge organizations in achieving their targeted goals. This is particularly true in the field of aerospace and automotive industry, where saving weight is directly related to the increase in efficiency and performance of any vehicle. The aim here is to reduce the weight of the structure without compromising the balance between strength, rigidity, and performance parameters.[1,2] This has become achievable with the advent of fiber-reinforced composite materials and the intensive use of composite materials in every major industry is proof of it. However, the joining of composite material remains a challenge for manufacturers as conventional mechanical joining methods like bolting and riveting can damage the composite fibers and create local defects around the bolt and rivet holes. Adhesive bonding has emerged as a potential substitute that has shown the ability to counter the demerits of the conventional mechanical joining methods by distributing the load over a larger area. Other advantages that adhesive bonding offers are: resistance against corrosion and fatigue, no heat effects as observed in welding, dimension stability, low shrinkage, joining of metals and nonmetals, and most importantly joining of thin-walled structures without damage.[3–6]
One-Story Three-Dimensional Frame Structures Behavior Strengthened with External Shear Wall under Cyclic Loading: An Experimental Study
Published in Journal of Earthquake Engineering, 2022
Hurmet Kucukgoncu, Fatih Altun
In structural engineering, the term ‘stiffness’, referring to the rigidity of a structural element, is defined as a measure of being able to resist deformation or deflection by the structural element under an applied force. As the stiffness of structural bearing systems increases, the lateral force required for deformation of the system must be increased. It is known that degradation in stiffness of a specimen occurs due to the formation of plastic hinges under lateral loads in the experimental research. For comparison of the stiffness values of the test frames, stiffness was investigated. The stiffness of a test specimen was determined by using the slope of the load-displacement graph for each pull and push cycle. Hence, the lateral load values obtained from the lateral load-displacement curve in each cycle are represented as F1 and F2, while the horizontal displacement values corresponding to these load values are referred to as δ1 and δ2. Then the stiffness value (ϕ) of that cycle was calculated using Eq. (1) as follows;