Load versus elongation curves

Figure 8.4 shows generic load versus elongation curves for rubbery amorphous, glassy amorphous, and semicrystalline polymers. In each case, the effect of extension on a dogbone specimen is shown at various points along the curve. 

Examples of load versus elongation curve characteristics of the pullout tests are shown in Fig. 9.6 for different hgnoceUulosic fibers embedded in thermoset polymeric matrices. 

Fig. 9.6 Load versus elongation curves directly obtained frinn a digital acquisition data of the tensile machine (a) sisal fiber/polyester - 5 nun (b) coir fiber/epoxy -15 mm coir fiber/polyester - 20 mm and (d) piassava fiber/polyester - 40 nun...

The tests are performed under carefully controlled stress (load), temperature, time, and creep (elongation) conditions. To save time, tests for different constant loads are performed simultaneously on different specimens of the same material. Creep tests may be rather extensively conducted, as for example when developing creep data prior to the design and fabrication of the first all-plastic airplane (41). The usual procedure is to plot the creep versus time curve, but other combinations are possible. 

Fig. 6.1 a A schematic creep curve showing three stages of creep and an instantaneous elongation on application of load b schematic strain rate plot versus time [69]... 

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