Reinforcing efficiency

If the matrix in 3.7 was reinforced with the same volume fraction of glass but in the form of randomly oriented glass fibres rather than continuous filaments, what would be the tensile strength of the composite. The fibres are 15 mm long, have an aspect ratio of 1000 and produce a reinforcement efficiency of 0.25. The fibre strength is 2 GN/m and the shear strength of the interface is 4 MN/m". 

Comparison of Reinforcing Efficiency of VDF-TFE Copolymers Relative to Silica Flour in Fluorosilicone Elastomers... 

Recently, some models (e.g., Halpin-Tsai, Mori- Tanaka, lattice spring model, and FEM) have been applied to estimate the thermo-mechanical properties [247, 248], Young s modulus[249], and reinforcement efficiency [247] of PNCs and the dependence of the materials modulus on the individual filler parameters (e.g., aspect ratio, shape, orientation, clustering) and on the modulus ratio of filler to polymer matrix. 

Young s modulus of the block copolymer fibers compared favorably with that of the physical blends as shown in Table 6, and in general they follow the linear rule of mixtures. The modulus data suggested that one does not need very large PBZT molecules to have the reinforcing efficiency. From the tensile data, one clear trend is that the tensile strength of the block copolymer system is much... 

An alternate approach was the synthesis [85,86] of PBZT copolymers (XIX) containing pendent 2,6-dimethylphenoxy graft sites. Such copolymers do not lead to any breaks within the rigid-rod backbone thereby, they have no adverse effects upon rod reinforcement efficiency. Using the conventional PBZT polymerization procedure, 2-(2,6-dimethylphenoxy)terephthaloyl chloride was substituted for terephthaloyl chloride up to 30 mol %. The pendent dimethylphenoxy copolymers were then reacted with m-phenoxybenzoic acid in PPMA. 

Cellulosic fiber reinforced polymeric composites find applications in many fields ranging from the construction industry to the automotive industry. The reinforcing efficiency of natural fiber is related to the namre of cellulose and its crystallinity. The main components of natural fibers are cellulose (a-cellulose), hemicelluloses, lignin, pectins, and waxes. For example, biopolymers or synthetic polymers reinforced with natural or biofibers (termed biocomposites) are a viable alternative to glass fiber composites. The term biocomposite is now being applied to a staggering range of materials derived wholly or in part from renewable biomass resources [23]. 

The fraction of reinforcing material in the filler space, is the parameter of reinforcing efficiency and can be easily calculated from the experimental data. The efficiency of the blend preparation method can thus be estimated by means of values or by means of the limit value (Cr)o o case of the average... 

Wang, Z. Ciselli, P. Peijs, T. (2007) The Extraordinary Reinforcing Efficiency of Single-Walled Carbon Nanotubes in Oriented Poly(vinyl alcohol) Tapes. Nanotechnol. Vol.18, No.45,455709... 

Shokrieh, M. M. and Rafiee, R., Investigation of nanotube length effect on the reinforcement efficiency in carbon nanotube based composites. Composite Structures, 92, 2415-2420 (2010). 

The shapes of the particles used in nanocomposites can be roughly spherical, fibrillar or platelets, and each shape will result in different properties. For maximum reinforcement, platelets or fibrillar particles would be used, since reinforcement efficiency is related to the aspect ratio (length/diameter. Lid). The most extensive research has been performed with layered silicates, which provide a platelet reinforcement [19]. 

An additional advantage of using a fiber-like reinforcement over a platelet-like reinforcement is its higher reinforcing efficiency in case of unidirectionally aligned systems [8], as can be demonstrated by micromechanical models like Halpin-Tsai [9]. A particle is said to reinforce efficiently a polymeric matrix if the increase in Young s modulus is close to the theoretical limit given by the rule of mixtures [10]. 

Another key factor in governing the reinforcement efficiency of filler is its surface area. Ideally, the dispersion of silica in NR-silica composite should be as homogeneous as possible and less silica-silica interaction. This chapter will focus on NR-silica nanocomposites obtained through various approaches as reported in the literature. It is worth noting that from the aspect of sustainable development, NR-silica nanocomposite provides the opportunity for greener products where carbon black is either totally or partially replaced by silica. 

In the case of filled vulcanizates, the reinforcement efficiency depends on a complex interaction of several filler-related parameters including particle size, particle shape, particle dispersion, surface area, surface activity, structure of the filler, and interactions between the fillers and the rubber matrix. 

The properties of a composite are dictated by the intrinsic properties of the constituents which may be summarized as fiber architecture and fiber-matrix interface (Fowler et al. 2006). The reinforcing efficiency of natural fibers depends on their physical, chemical, and mechanical properties. Major shortcomings of natural plant fibers include fiber nonuniformity, property variation even between individual plants, low degradation temperature, low microbial resistance, and susceptibility to rotting. In addition to naturally occurring nonuniformity, fiber extraction and processing techniques also have major impacts on final fiber quality, not to mention fiber costs and yield (Munder et al. 2005). 

Unlike in the case of spherical inclusions where the rigid inclusions cause stiffening of the composite by excluding volume of a deformable mattix, the presence of an interphase layer affects the tme reinforcing efficiency of the inclusions. Hence, the effective filler modulus of the inclusions have to be calculated as a function of interphase thickness and elastic modulus. This can be done effectively using simple rule of mixture ... 

Jancar et al. (154) attempted to calculate the effect of a soft interphase on the stress field around and in the platelet shaped and fibrous inclusions of small aspect ratio. Because of the presence of a shear component of the stress in the interphase, a transfer of a portion of the load from the matrix to the core-shell inclusion is possible, even when the interphase layer has modulus of elasticity substantially lower than the matrix. At least five to six times thicker soft interphase compared with spherical inclusion is necessary to reduce the reinforcing efficiency of platelets with aspect ratio of 5 to a negligible value. Above the elastomer interphase volume fraction equal to about 12 vol% of the inclusions, the elastic modulus of the complex core-shell inclusion equals that of the PP matrix. 

Li H et al (2013) The reinforcement efficiency of carbon nanotubes/shape memory polymer nanocomposites. Compos B Eng 44(1) 508-516... 

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