Tensile strength and modulus

Tensile strength is the maximum tensile stress which a material is capable of developing. It is calculated from the maximum load carried during a tensile test and the original cross-sectional area of the specimen. The type of specimen to be used is prescribed in ISO 527 and 3268 (the latter deals exclusively with glass fibre composites and describes some special forms of test specimens). 

The tensile test provides an insight into the stress/strain behaviour of a material under uniaxial tensile loading and makes it possible to distinguish between brittle and ductile materials. It is a useful tool for quality control and general comparison of properties, but it cannot be considered representative for applications with load/time scales widely different from those of the standard test. 

The tensile modulus is taken as the tangent to the initial linear part of the 

Flexural strength is determined on bar-shaped specimens with rectangular or circular cross-section, by supporting the specimen horizontally and applying a load vertically. The deformation of the flexed beam generates tensile and compressive stresses in the outer layers of the specimen, with a neutral zone approximately in the middle. Shear stress may develop along the neutral axis, depending on the ratio of support distance to specimen thickness used. 

Generally a span/thickness ratio of 16 is used but, for materials which tend to fail in an interlaminar shear mode (such as unidirectionally reinforced composites), a ratio of 20 is to be preferred. Flexural strength is a convenient method for comparing properties, because it involves a stress/deformation mode that is often encountered under service conditions, and the test specimens are relatively small. 

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Tensile strength and modulus of rigid foams have been shown to vary with density in much the same manner as the compressive strength and modulus. General reviews of the tensile properties of rigid foams are available (22,59,60,131,156). 

Polyester. This fiber has several performance advantages versus polypropylene, although it is less economical. Polyester can produce higher tensile strength and modulus fabrics that are dimensionally stable at higher temperatures than polypropylene. This is of importance in selected appHcations such as roofing. Polyester fabrics are easily dyed and printed with conventional equipment which is of extreme importance in apparel and face fabrics although of lesser importance in most spunbonded appHcations (see Fibers, polyester). 

Aramid Fibers. Aromatic polyamide fibers exhibiting a range of mechanical properties are available from several manufacturers, perhaps the best known being Du Pont s proprietary fiber Kevlar. These fibers possess many unique properties, such as high specific tensile strength and modulus (see Fig. 4). Aramid fibers have good chemical resistance to water, hydrocarbons, and solvents. They also show excellent flame retardant characteristics (see High PERFORMANCE fibers Polyamdes). 

The absorbed water has a plasticising effect and thus will cause a reduction in tensile strength and modulus, and an increase in impact strength. As has already been mentioned the presence of absorbed water also results in a deterioration of electrical properties. 

Since weight is frequently a factor in the applications of composite structures, values for eleetrical and thermal conductivity, and tensile strength and modulus are even more impressive when normalized by the mass of the fiber. 

A reinforced plastic sheet is to be made from a matrix with a tensile strength of 60 MN/m and continuous glass fibres with a modulus of 76 GN/m. If the resin ratio by volume is 70% and the modular ratio of the composite is 25, estimate the tensile strength and modulus of the composite. 

The effect of ionomer concentration on the mechanical properties of PP-EPDM blends is given Table 9. It is seen that the tensile strength and modulus show a maximum at 5 wt% of both ionomer A and B, thereafter, it decreases at higher ionomer loading. The properties are higher for ternary blends containing ionomer B than these containing ionomer A. On the other hand, addition... 

The presence of a few atomic percent of oxygen in tantalum increases electrical resistivity, hardness, tensile strength, and modulus of elasticity, but decreases elongation and reduction of area, magnetic susceptibility, and corrosion resistance to HF . 

Figure 3.17 shows the mechanical properties of the ACM-silica and ENR-silica hybrid composites synthesized from various pH, reproduced from the data reported by Bandyopadhyay et al. [36]. As morphology indicates, all the samples prepared within the pH range 1.0-2.0 are transparent, contain nanosilica particles, and are superior in tensile strength and modulus... 

FIGURE 31.13 (a) Plot showing the stress-strain behavior of various irradiated rubbers, (b) Plot showing the variation of tensile strength and modulus of rubbers irradiated with different doses, (c) Plot showing the variation of hysteresis loss, set, and elongation at break of irradiated fluorocarbon rubbers. (From Banik, I. and Bhowmick, A.K., Radial. Phys. Chem., 54, 135, 1999. With permission.)... 

Extensive product trials using the LCBM technique in standard tire recipes have proved that the tensile strength and modulus, elongation at break, compound hardness, abrasion loss, and hot air aging properties have improved substantially compared to mixes prepared using conventional technique. 

FIG. 9 Dependence of tensile strength and modulus on clay loading for epoxy-CH3(CH2)i7NH -montmorillonite nanocomposites. (From Ref. 35.)... 

Ultrahigh molecular weight ultra-oriented fibers have outstanding tensile strength and modulus, which suits them for use in bullet proof vests. 

SA fiber showed high tensile strength and modulus of over 2.5 GPa and over 300 GPa, respectively. The initial strength was preserved after heat-treatment... 

Dielectric constant and dissipation factor measurements were conducted according to the procedures of ASTM D-150-87. Tensile strength and modulus and percent elongation were measured on an Instron model 1125 according to the procedures of ASTM-D-882-83. 

However, there remain numerous end-use applications which require significant improvements in the properties PET has to offer. These include higher tensile strength and modulus for tyre reinforcement yams and monofilament applications, higher temperature resistance for hot-fill containers and films, and greater gaseous barrier for longer shelf-life requirements (e.g. fruit juice and beer markets). 

Table 3.4 Examples of reinforcement ratios based on tensile strength and modulus...

Unfortunately, they can have some drawbacks, such as decreased tensile strength and modulus, pollution, toxicity, migration or environmental risks, and the local and professional regulations, standards and specifications must be studied. 

Figure 4.126 ((a) and (b)) shows tensile strength and modulus versus temperature for samples that are identical except for the thickness, which is 1 mm for one and 4 mm for the other. The gap decreases when the temperature rises but at room temperature is 26% for strengths and 45% for moduli. 

It should be recalled that the tensile strength and modulus of composites are often mainly determined by fibre performances, the matrix having a lesser effect. In contrast, the continuous use temperature generally depends on the matrix. 

Medium to low tensile properties according to the tensile properties of the core. The tensile strength and modulus of a lOOkg/m foam are roughly as low as 3 MPa and 0.1 GPa, respectively. 

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