Test lengths

As is the case with glass fibers, the tensile strength of natural fibers depends on the test length of the specimens. Examinations were made by Kohler et al. [8],... 

Figure 3 Dependence of tensile-strength on test length, flax fibers [70], and pineapple fibers [88] compared with textile glass-fibers [8].

Fig. 2 Weibull plot of the filament strength for a test length of 10 cm of a PpPTA yarn yielding a Weibull modulus of 20.6. The average filament strength is 3.2 GPa... 

The average fracture stress of the filaments for a test length L is given by... 

Fig. 3 The natural logarithm of the average filament strength (n=40) as a function of the natural logarithm of the test length for an intermediate-modulus, PAN-based carbon fibre with an impregnated bundle strength of 5.7 GPa [8]...

The strength of a fibre is not only a function of the test length, but also of the testing time and the temperature. It is shown that the introduction of a fracture criterion, which states that the total shear deformation in a creep experiment is bounded to a maximum value, explains the well-known Coleman relation as well as the relation between creep fracture stress and creep fracture strain. Moreover, it explains why highly oriented fibres have a longer lifetime than less oriented fibres of the same polymer, assuming that all other parameters stay the same. 

Flame Test(Length and Duration of Flame Determination) (Gross und Dauer von Spreogstoff-Flommen ... 

Results + + + denotes very strongly positive + + denotes strongly positive + denotes faintly positive test length of inhibition period depends on distance of ultraviolet source and H202 concentrations... 

Sample Description Moisture Test Length Fines... 

The exposure time was originally selected because the anticipated test length was only a few seconds. It was felt that an hour of temperature exposure would well exceed the lifetime of any experimental test series. This exposure time was selected to make this work consistent with earlier research.To date, no research had been completed comparing the effects of exposure time at temperature to the magnitude of fluorescence emission. It was decided to complete a series of tests with a single binder to determine the relationship between temperature exposure time and normalized emission intensity for a Y2O3 Eu and Resbond 793 TSP. 

Mechanical properties (stress-strain) were measured on an Instron tester at a cross head speed of 10 mm/min. Dumbbells shaped samples were cut with a die and had an 8 mm test length and a thickness of no more than 0.5mm. Additional details may be found in the thesis work of one of the coauthors (C. W. C.) (14). 

Figure 7 A typical load/extension (stress versus strain) curve for a yam from the Victory sail. Typically, a test length of 2.5cm was set...

Taking account of all the available evidence, a tenacity of 70g/tex is a reasonable middle value for a wide range of jute fibers, based on single fiber test lengths of 10 mm or less, and a time to break of 10 s. This value of tenacity is appropriate to fibers of linear density 1.8 tex, and it is important to state the linear density, because, statistically, an increase of 0.1 tex reduces the tenacity by about 1.5 g/tex. This inverse dependence of tenacity on linear density is common to most fibers and also to fine metal wires. 

In the decade after 1995, Petrobras installed 20 rigs off the coast of Brazil (Fig. 13.22). These have been monitored and have performed well. Test lengths have been removed for examination. One unexpected problem was penetration of marine crustaceans at a particular depth. This could be overcome by inserting a section of wire rope. 

---