Mechanical properties tensile stress-strain

Mechanical Properties. The stress-strain curves were determined with an Instron tensile tester (Table Model 1130). The crosshead speed was 50 mm/min. The measurements were performed on wet 1.3-cm X 0.4-cm dog bone samples at room temperature. 

The effect of temperature on PSF tensile stress—strain behavior is depicted in Figure 4. The resin continues to exhibit useful mechanical properties at temperatures up to 160°C under prolonged or repeated thermal exposure. PES and PPSF extend this temperature limit to about 180°C. The dependence of flexural moduli on temperature for polysulfones is shown in Figure 5 with comparison to other engineering thermoplastics. 

Higher extent of silica generation with high TEOS concentration improves the mechanical properties severalfolds as illustrated by the tensile stress-strain plots on ACM-sdica hybrid nanocomposites on increasing TEOS concentrations in Figure 3.6. 

Families of tensile stress-strain curves have been generated for strain rates in the range of 10 - 10 s " at 23°C, for both the epoxy adhesives. These are illustrated in Fig. 4 (a) and (b). The tensile properties were found to increase progressively with the increasing the rate. Calculated mechanical properties are summarised in Table 3. The properties of the aluminium alloys are not significantly affected by the rates considered and may be regarded as rate independent [13], The mechanical properties of the aluminium alloys used in the current research are summarised in Table 4. 

The mechanical and thermal properties of a range of poly(ethylene)/po-ly(ethylene propylene) (PE/PEP) copolymers with different architectures have been compared [2]. The tensile stress-strain properties of PE-PEP-PE and PEP-PE-PEP triblocks and a PE-PEP diblock are similar to each other at high PE content. This is because the mechanical properties are determined predominantly by the behaviour of the more continuous PE phase. For lower PE contents there are major differences in the mechanical properties of polymers with different architectures, that form a cubic-packed sphere phase. PE-PEP-PE triblocks were found to be thermoplastic elastomers, whereas PEP-PE-PEP triblocks behaved like particulate filled rubber. The difference was proposed to result from bridging of PE domains across spheres in PE-PEP-PE triblocks, which acted as physical crosslinks due to anchorage of the PE blocks in the semicrystalline domains. No such arrangement is possible for the PEP-PE-PEP or PE-PEP copolymers [2]. 

Tensile, compressive, flexural rearrangements of a sample morphology result in a dimensional change to the sample in response to an applied external force. The nature of the response and its intensity can be correlated with morphological and molecular characteristics of the sample. Two of the most important mechanical properties are stress and strain of materials and profiles, developed under a series of loads. The ultimate stress of the materials is often expressed as strength and the initial (transient but sustained) strain as a function of load is expressed as modulus of elasticity. This is related to both tensile and compressive properties. 

The low-speed mechanical properties of polymer blends have been frequently used to discriminate between different formulations or methods of preparation. These tests have been often described in the literature. Examples of the results can be found in the references listed in Table 12.9. Measurements of tensile stress-strain behavior of polymer blends is essential [Borders et al., 1946 Satake, 1970 Holden et al., 1969 Charrier and Ranchouse, 1971]. The mbber-modified polymer absorbs considerably more energy, thus higher extension to break can be achieved. By contrast, an addition of rigid resin to ductile polymer enhances the modulus and the heat deflection temperature. These effects are best determined measuring the stress-strain dependence. 

The stress-strain test (tensile test) is the most common mechanical test used for polymers. This test is conducted by fixing the polymer sample at one end to a loading frame, and a force is applied at the other end to achieve a controlled displacement d (see Figure 20.1a). A stress-strain curve (Figure 20.1b) is obtained and analyzed to provide the mechanical properties. The stress (defined using the following equations ... 

The cast SELP-47K films are not mechanically stable after hydration [65, 67] and it is therefore necessary to stabilize its structure. Methanol induces the crystallization of the silklike blocks, leading to aqueous insolubility, and improves the mechanical properties by the conversion of less-ordered conformations into more ordered anti-parallel beta-sheet structures [87,88]. Under uniaxial tensile stress-strain, fully hydrated treated films exhibited an ultimate... 

The most important mechanical property of a plastic is its tensile stress-strain curve (Figs. 10-1 and 7-4). This curve is obtained by stretching a sample in a testing machine and measuring its extension and the load required to reach this extension. Plastics show viscoelastic behavior (as reviewed in Chapter 1) that is highly sensitive to temperature and, in some materials, to relative humidity variations so it is important to use samples of standard shapes, preconditioned at constant and standard temperature and relative humidity before testing. Requirements are explained in the ASTM specifications. 

The effect of the CNT loading on mechanical properties of the come fibrefiber (2x drawn) was investigated and the tensile stress-strain curves are shown in Figure 5. For imdoped PANi, the addition of 2% w/w CNTs increased the yield stress by 100%, the tensile stress (Oj by 50%, the Young s Modulus (E) by more than 200% compared to the neaniline fiber. A 30% decrease in elongation at break (e ) also occurred (Table 1). 

By far the greatest share of both experimental studies of mechanical properties of fibres and theoretical studies of structural mechanics has been on tensile properties. This paper therefore concentrates on explanations of tensile stress-strain curves and the way in which they lead to fracture. Some comments on other forces, particularly in cyclic loading, will be included in a concluding section. 

In addition to offering resistance to degradation at high temperatures, polysulfones maintain their mechanical properties at high temperatures without reinforcement. The effect of temperature on PSF tensile stress-strain behavior is shown in Fig. 13.2. It can be seen that the retention of useful properties extends to approximately 150°C for PSF. This useful temperature range approaches 180°C for PES and PPSF... 

Mechanical Properties. The tensile stress-strain behavior of ethylene-co-styrene polymers, including the effects of crystallinity and molecular weight, has been extensively reported and analyzed. Figure 5 presents tensile stress-strain data for a series of copolymers differing primarily in styrene content. The copolymers generally exhibit large strain at ruptiu e, and have been foimd to show uniform deformation behavior (46). 

While the water absorbtion of PPO -PA blend is a straight function of the polyamide content (fig.10), the net effect on the mechanical properties shows major synergism as Indicated in the tensile stress-strain diagram (fig. 11) where the dry as molded and 50 % relative humidity conditioned PP0 /PA blends maintains very close properties. A major drop In tensile strength is observed for Its parent polyamide 66. 

Attempts to improve the mechanical properties have focused on biocompatible plasticizers. Blending with PEG, the conventional name for low molecular weight (<20 000) PEG, improves elongation at break and softness of PLA. At ambient temperature, the desired mechanical properties are achieved by blending PLA with 30 wt% PEG Table 4.2 shows the effect of PEG content on the thermal and mechanical properties of quenched PLA/PEG blends. However, there is evidence that the blend is not stable and the attractive mechanical properties are lost over time. The dynamic mechanical relaxation behavior and tensile stress-strain behavior of PLA and PLA/PEG blends are shown in Figs. 4.19 and Fig. 4.20 respectively. 

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