Flexural strain

Fig. 8.8. Correlation of residual compression-after-impact (CAI) strength with resin flexural strain to...

Figure 10. The EE, AE, and load accompanying the flexural straining of (a) (0)jg and ( b)( 45)jg graphite/epoxy laminates (Thornel 300/NARMCO 5208).

Fiber type 90 flexural strength (MPa) 90 flexural strain (%) Tangent modulus of elasticity (GPa)... 

This increase in stability, however, is accomplished at the sacrifice of mix flexibility. The data in Table IV indicate that the flexural strain at break of mixes No. 3 and 4 is reduced significantly below that of mixes No. 1 and 2 when the sulfur concentration in the binder is raised to 40 and 50 wt %, without increasing the total binder content. Flexibility is a measure of mix susceptibility to brittle fracture and is an important mix design consideration in rigid materials to prevent premature pavement cracking. 

Because of its higher rigidity at warm temperatures, sand Thermopave formulations are not as flexible as asphalt concrete mixes. A typical sand Thermopave mix (6 wt % asphalt 12 wt % sulfur) exhibits a flexural strain at break of 0.004 cm/cm under the same test conditions as indicated in Table IV. Although this is below the strain values for asphalt concrete, lower flexibility in Thermopave can be tolerated as the tensile stresses and strains developed at the underside of the pavement are lower than for an asphalt pavement of equivalent thickness and subjected to the same loading. Performance of test pavements to date, some over six years old, have not indicated flexibility to be a problem as yet. 

Another bent-strip method for evaluating the ESCR is presented in ISO 4599. In this test, strips of a plastic are positioned in a fixed flexural strain state and exposed to a stress cracking agent for a predetermined period. The test is uniaxial and simple to perform, and the deformation is constant. Because of the molecular chain relaxations, the stress state is well defined only at the beginning of the test. After exposure to the medium, the strips are removed from the straining rig, examined visually for changes in appearance, and then tested for some indicative property such as tensile strength. 

The flexural and tensile properties of polyester composites at various fiber volume fractions are listed in Table I. Strength values increase up to a fiber volume fraction of about 40% but then decrease with increased fiber volume fraction. This is caused by the poor wetting and extensive fiber damage which occurs at higher volume fractions because of compaction and close packing of the fibers. The ultimate flexural strain shows a similar trend. The modulus values increase almost linearly with fiber volume fraction. 

Compressive Strain - The relative length deformation exhibited by a specimen subjected to a compressive force. See sAso Strain, Flexural Strain, Tensile Strain. 

Flexural Strain - The tensile elongation on the surface of a cross section opposite to that experiencing a locally impinging force in bending at any time of the test. See also Strain, Compressive Strain, Tensile Strain. 

Strain - The per unit change, due to force, in the size or shape of a body referred to its original size or shape. Note Strain is nondimensional but is often expressed in unit of length per unit of length or percent. Also called mechanical strain. See also Flexural Strain, Compressive Strain, Tensile Strain. 

Table 9.12 Chemical resistant loss in tensile strength and flexural strain of glass fiber/thermoplastic (wt%) (courtesy of LNP)...

Flexural stress Flexural strain Modulus of elasticity (as average of the tension and the compression)... 

Sic particles and undoped AI2O3 of the same grain size. The hatched band represents flexural strain rate data for... 

On the basis of the stress-strain diagram registered (Fig. 4.40) the flexural strength cTfM (Eq. 4.30) and the associated flexural strain fM and flexural strain at break SfB can be calculated. Because of the dependence on software and test equipment the flexural stress at break CfB is not used. If the specimen fails to break,... 

Fig. 7. EE, AEr and load accompanying the flexural straining of 16 layer unidirectional graphite-epoxy composite (20).

Flexural strain reflects the flexibility of a material. Highly flexible resins like rubbery epoxy, polyurethane, and modified resins do not break even after a large deflection determination of ultimate flexural strength is impractical for them. The relevance of mechanical tests depends on the form in which the material is going to be used. If a material is to be used as a beam, then a flexural test is more relevant than a tensile test. 

Three-point flexural tests provide values for the modulus of elasticity in bending, flexural stress, flexural strain, and the flexural stress-strain response of the tested material [63, 64], i.e., the determination of strain recovery and stress recovery ratio. 

Exp. No. Reinforce-ment Glass content, %(m/m) Void content, %v Flexural modulus GPa 95 % CL Flexural strength MPA 95 % CL Flexural strain at break, %... 

S. Wang and D. D. L. Chung, Self-Sensing of Flexural Strain and Damage in Carbon Fiber Polymer-Matrix Composite by Electrical Resistance Measurement, Carbon, 44 [13] 2739-2751 (2006). 

Flexural strain at break (%) ISO 178 No break No break No break... 

Wang, S., Chung, D., 2006. Self-sensing of flexural strain and damage in carbon fiber polymer-matrix composite by electrical resistance measurement. Carbon 44 (13), 2739-2751. 

Cyclic behavior in fiber composite plastics is determined by tensile/compressive-swell or by cyclic flexural tests. While normal stress or also deformation can be kept constant for tensile/compressive swell tests, in cyclic flexural tests a flexural strain is typically set and the damage state defined by a certain stress reduction. 

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