Flexural creep

Table 2-7 Flexural creep data of reinforced plastics at 23°C...

ISO 899-2, Plastics - Determination of creep behaviour - Part 2 Flexural creep by three-point loading, 1993. 

Procedures are given in ISO 899 Parts 1 and 2 for tensile and flexural creep respectively [16, 17]. Creep is also considered in Section 6.9. 

ASTM D2990, a, Test Methods for Tensile, Compressive and Flexural Creep and Creep Rupture of Plastics, Vol. 8.02, ASTM, Philadelphia, Pa., 1993. 

Fig. 4.5 Comparison of flexural creep of whisker-reinforced A1203 with that of whisker-free aluminum oxide. A sharp increase in the stress exponent is observed at the higher stresses for the whisker-reinforced materials tested at 1400°C. Figure from Ref.

Fig. 5.7 Macroscopic damage modes that occur during the tensile and flexural creep of fiber-reinforced ceramics. It is assumed that matrix or fiber damage is avoided during initial application of the creep load (see discussion of loading rate effects in the next section). Periodic fiber fracture can occur if the creep rate of the matrix exceeds that of the fibers. Periodic matrix fracture is common when the matrix has a higher creep resistance than the fibers. In this figure, it is assumed that initial microstructural damage is avoided during application of the creep load.

Flexural Properties (see also Flexural Creep) ASTM C 203 (R) (TM)... 

ASTM C 480-62 (1988) Standard Test Method for Flexure-Creep of Sandwich Constructions, 2 pp (Comm F-7)... 

K.C.Kyriacou (1991). Accelerated Compression and Flexural Creep Testing of Polymer Concrete. Ph.D. Dissertation, The University of Texas. 

Figure 3.80 Flexural creep of various grades of PVDF as a function of stress, time, and temperature.

Figure 3.81 Flexural creep resistance of various grades of PVDF at 0.7 MPa and 140°C.i >...

In a creep test, the load on the test piece is kept constant, and the dimensional changes that this brings about are monitored as a function of the lime. Internationally, there are two standards available for the evaluation of creep properties of plastics ISO 899-1 [108], which deals with tensile creep, and ISO 899-2 [109] (formerly ISO 6602), which deals with flexural creep. In both of these standards the initial stress, i.e., the stress based on the original (unloaded) dimensions of the test piece is assumed (as it is for the corresponding short-term tensile and flexural strength tests), and the strain is similarly defined as for the short-term strength tests, except, of course, that in this case, it is the strain as a function of time that is of paramount interest (Fig. 22a). The term creep strain is used to differentiate this type of strain from the short-term strain induced by classical tensile and flexural tests. The modulus is defined as the ratio of the initial stress to the creep strain and is referred to as the "creep modulus." Since the stress is constant and the strain increases with time, it follows that the creep modulus decreases as lime increases. Other properties of interest when conducting creep tests arc... 

ISO 899-2. Plastics—Determination of creep behaviour—Part 2 Flexural creep, 1993. 

ASTM D2990, Tensile, compressive and flexural creep and creep-rupture of plastics, 1995. 

Figure 7.30 Reinforcement and filler inverse effect on flexural creep rate (courtesy of LNP)...

The most common technique employed to date has been that of creep in uniaxial tension. It was shown above that with the inclusion of lateral strain measurements this is a powerful technique giving access to up to 6 independent creep compliance functions. This is more than for any other known method. It further has the overwhelming advantage over many methods, such as say torsional or flexural creep, that the stress is sensibly uniform over the working volume of the specimen. This advantage is paramount in studies of materials displaying non-linear behaviour in creep since analysis of the non-uniform stress situation in non-linear systems is not well developed. Attempts to overcome the non-uniform stress situation in torsion, by recourse to, say, torsion of thin walled tubes, lead to severe difSculties in specimen preparation in oriented materials, when anisotropy of behaviour is to be studied. 

Ecfioo MPa flexural-creep modulus after 100 hours... 

Standard test method for tensile, compressive, and flexural creep and creep-mpture of plastics... 

Long-term Loading - Flexural Creep Test - Introduction... 

For a constant stress level the flexural-creep modulus E f is be calculated using the time-dependent deflection and Eq. 4.51. The flexural-creep strength is determined in accordance to Eq. 4.52. 

Fig. 4.159 Principle of flexural creep test with three- (a) and four-point bend test equipment (b).

Differing to the regulations of the standard ISO 899-2 the flexural-creep modulus is designated as symbol cf- The frequently used values in the following Table are the modulus at 1 hour E i, at 100 hours cnoo and at 1000 hours Fcfiooo-... 

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