Unidirectional fiber

Boron fibers exhibit the highest stiffness and strength efficiencies in Figure 1-24. When placed in a lamina as unidirectional fibers, the... 

Figure 3-2 Representative Volume Element - Lamina with Unidirectional Fibers...

The results of the micromechanics studies of composite materials with unidirectional fibers will be presented as plots of an individual mechanical property versus the fiber-volume fraction. A schematic representation of several possible functional relationships between a property and the fiber-volume fraction is shown in Figure 3-4. In addition, both upper and lower bounds on those functional relationships will be obtained. 

A unidirectional fiber-reinforced composite material deforms as the load increases in the following four stages, more or less, depending on the relative brittleness or ductility of the fibers and the matrix ... 

C. C. Chamis, M. P. Hanson, and T. T. Serafini, Impact Resistance of Unidirectional Fiber Composites, in Composite Materials Testing and Design (Second Conference), H. T. Corten (Chairman), Anaheim, California, 20-22 April 1971, ASTM STP 497, American Society for Testing and Materials, 1972, pp. 324-349. 

In general, the compressive strength of a non-reinforced plastic or a mat-based RP laminate is usually greater than its tensile strength. The compressive strength of a unidirectional fiber-reinforced plastic is usually slightly lower than its tensile strength. Room-temperature compressive stress-strain data obtained per ASTM for several plastics are shown in Table 2-5. 

For the representative volume element of a unidirectional fiber-reinforced composite, consisting of a cluster of three co-axial cylinders of the same height, equal to unity, the following relations hold (Fig. 13) ... 

Therefore, all the theory, sketched previously for particulates, is also valid for the fiber composites, the only difference being in the evaluation of the radius rs of the mesophase. Indeed, in order to define the radius rs of the cylindrical layer, corresponding to the mesophase for the fiber composites, we express it as r, = (rf + Ar) and we modify the respective relation given by Lipatov 11) for particulates to the appropriate relation for cylindrical inclusions. For the cases of unidirectional fiber-reinforced composites, it may be shown that the following relation holds ... 

Unicracking process, 16 842—843 Unidendate ligands, 7 575, 13 443 Unidirectional diffusion, 1 40-41 Unidirectional fiber composites fabrication of, 26 766—767 Unidirectional lamina... 

The [10°] off axis tension specimen shown in Fig 3.23 is another simple specimen similar in geometry to that of the [ 45 ]s tensile test. This test uses a unidirectional laminate with fibers oriented at 10° to the loading direction and the biaxial stress state (i.e. longitudinal, transverse and in-plane shear stresses on the 10° plane) occurs when it is subjected to a uniaxial tension. When this specimen fails under tension, the in-plane shear stress, which is almost uniform through the thickness, is near its critical value and gives the shear strength of the unidirectional fiber composites based on a procedure (Chamis and Sinclair, 1977) similar to the [ 45°]s tensile test. 

ASTM D 5528 (1994). Mode I interlaminar fracture toughness of unidirectional fiber-reinforced polymer matrix composites. 

Fig, 6.17. Fracture process zone (FPZ) in transverse fracture of unidirectional fiber composite. After... 

Tohgo, K. Wang, A.S.D. and Chou, T.W. (1993). A criterion for splitting crack initiation in unidirectional fiber-reinforced composites. J. Composite Mater. 27, 1054-1076. 

Jayaraman, K. and Reifsnider, K.L, (1993). The interphase in unidirectional fiber reinforced epoxies effect on residual thermal stresses. Composites. Sci. Technol. 47, 119-129. 

Figure 4.14 Schematic diagram of the melt infiltration process for flow past a unidirectional fiber assembly.

Person 1 Calculate the permeability, Ko, for the case of a fiber preform made from unidirectional fibers of diameter 10 (xm, and a porosity of 60%. 

---