Fibers tensile strength values

A statistical analysis of the liber tensile strength values determined on a series of fiber samples can be easily made by using the two-parameter Weibull distribution described above. Using the form of the Weibull expression given in Eq. (10.2), we can write the probability of failure F(o) of the liber at a stress a, as... 

Fiber property Different grades of each fiber exist so that properties can change. Typical tensile strength values in Ib/in (g/cm ) are ... 

The mechanical properties of the fibers do not depend on the crystallite orientation, but they do depend on the tie molecules between the crystallites (see also Section 5.4.2). These bundles of tie molecules or strands can transport forces very effectively. It is important to note that laboratory-produced fibers often have defects, and in comparing the tensile strengths of these with industrially produced fibers, one should always take the highest tensile strength value of such laboratory produced fibers. Otherwise, one is comparing the faults and defects of the fibers and not the influence of structure. 

Figure 3.26 Comparison of tensile strength values for polyamide and polypropylene glass fiber types. , PPG 3242 , PPG 3540. (From Uniroyal Chemical Co., Ino., literature.)...

As the average fiber length increases to >5 Ac, the tensile strength values reach a plateau. 

The measured tensile strength Oo- using a molded ASTM tensile specimen was used to define the boundary value at 0 = 0, i.e. o(0) = Gir. In Fig. 12.27, each material exhibits a parabolic-shaped curve suggesting transverse tensile behavior typical of the shear failure in the fiber-matrix interface. Based on Lees (32), the minimum tensile strength value for each curve approximates o(45°) for the given composite material. By substituting the value of o(45°) into Eq. (12.9), the effective interfacial shear strength value was obtained x = sin (45°) cos (45°) g(45°) = (0.707)(0.707) 0(45°) = o(45°)/2. 

When Kevlar is used in reinforced composites, the values of tensile modulii may be near to those of the fiber itself, but the tensile strength values for the fibers may be quite different than the composite because of factors such as translation efficiency, possibility of flaws, processing damage, or incorrect fiber orientations. 

A combination of chemical and mechanical treatments was employed to prepare polypropylene matrix composites reinforced with treated coconut fibers by Gelfusol et al. [113]. The fibers were chemically treated (alkalization-CCUV samples) or mechanically treated (ultrasonic shockwave-CMUV samples) were dried using UV radiation. They concluded that CMUV samples containing 5 vol. (%) fiber presented superior tensile strength values ([Pg.387]

---