Unidirectional RPs

Figure 7.35 Examples of stress/strain curves for unidirectional RPs and metals...

Table 9.31 Properties of unidirectional RP graphite, boron, and aramid/epoxy RPs... 

Reasonably accurate analytical methods have been established for predicting elastic constants of a unidirectional RP. Using laminated plate and shell theory (macromechanics), the elastic constants of multidirectional RPs are derived from the elastic constants of the unidirectional layer (Chapter 8). In addition to the work on prediction of elastic constants, work has been done in predicting strength of multidirectional RPs based on experimentally determined strengths of unidirectional RPs. 

In calculating the effect of the twisting torque, the transverse shear modulus of the unidirectional RP has been used. For an RP with... 

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. 

Fig. 2-46 Sequence of push-pull fatigue in unidirectional glass-fiber/TS polyester RPs by mi-crobuckling processes.

The fiber content in mat or random fiber RPs is usually somewhat lower than for an isotropic laminate which is comprised of a number of unidirectional plies. Both laminates may, for example, be planar-isotropic. The random criss-cross nature of chopped fibers in a mat does not permit close packing of the bundles, and thus the fiber content is usually lower. With a lay-up of unidirectional plies, the packing of fibers within a ply may be very close, and the fiber content can be very high. The higher fiber content made from individual plies tends to make it stiffer and stronger than the mat construction. 

IEST-RP-CC002.2 Unidirectional Flow Clean-Air Devices, Jan. 19,1999. 

Still stronger and stiffer forms of fibrous materials are the unidirectional crystals called whiskers. Under favorable conditions, crystal-forming materials will crystallize as extremely fine filamentous single crystals a few microns in diameter and virtually fi-ee of the imperfections found in ordinary crystals. Whiskers are far stronger and stiffer than the same material in bulk form. To date their use is limited principally due to special handling requirement during fabrication into RPs and cost. 

Table 2.15 Properties of unidirectional carbon/aramid hybrid/epoxy RPs...

Other fiber configurations include chopped fibers, woven cloth, and laminates of unidirectional fibers. The process allows a light tough and highly stiff RP to be manufactured using only one phase of the material, which has considerable advantages over two-component RPs. 

Dow-United Technologies Composite Products Inc (Dow-UT), Wallingford, Connecticut, developed an advanced resin transfer molding (AdvRTM) process for production of complex and flight-critical airframe and engine structures in RPs. The process has been further developed to improve the quality of RP aerospace components substantially at the point where two or more sections are molded together. A patented technique of shaped unidirectional fiber preforms... 

Table 7.8 Examples of static mechanical properties of unidirectional fiber/epoxy RPs... 

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