Page 63 - Handbook of Properties of Textile and Technical Fibres

44 Handbook of Properties of Textile and Technical Fibres

to use these techniques only to obtain the initial fracture morphologies as the loads
recorded at failure may be altered by the medium around the fiber.

2.4.1.2 Single fiber tensile testing device

The testing of single fine fibers in tension, relaxation, creep, and fatigue has been
extensively studied by Bunsell et al. (1971) using a “universal fiber testing machine.”
These tests have revealed a distinctive tensile fatigue process in thermoplastic fibers
(Oudet and Bunsell, 1987; Marcellan et al., 2003; Herrera et al., 2006; Le Clerc
et al., 2007) and have also been used to characterize aramid (Lafitte and Bunsell,
1985) and carbon fibers (Bunsell and Somer, 1992) in fatigue. The mechanical part
of the machine is shown in Fig. 2.16. It is controlled electronically and permits high
loading precision. It can be used for the following:
• Tensile tests: by setting a constant deformation rate.
• Relaxation or creep tests: by either setting a constant deformation or a constant load. The
addition of a furnace has allowed evaluation of the creep of ceramic fibers at high tempera-
tures. In that context, fibers and the furnace had to be placed horizontally to maintain the tem-
perature as constant as possible along the fiber. This also facilitates mounting of the fiber in
the machine.
• Fatigue tests: setting the required mean load and amplitude of vibration controls, hence the
lower and upper limits of imposed cyclic load. The limiting loads are therefore symmetrical
about the mean load.

(a)

(b)

Figure 2.16 The mechanical part of a universal fiber testing machine and a zoom on the clamps.