Flexural modulus reinforced laminates

Table 111. The flexural strength and flexural modulus of the carbon fiber-reinforced RX-PTFE (RX-PTFE composite) and the carbon fiber-reinforced SX-PTFE (SX-PTFE composite). Volume of carbon fiber was 54.3 %, Sixth plys laminated panel.

Boron fibers have also been used in the form of epoxy prepreg tapes in which the filaments are carefully aligned and tensioned to provide a one-fllament-thick tape. Generally, these tapes are composed of 65-70 percent filaments in the epoxy resin matrix. The longitudinal flexural modulus of boron-epoxy laminates made in this way is about 27 X 10 psi, and the flexural strength is 280,000 psi. Boron fibers have also been applied to reinforce epoxy novolacs, phenolics, and polyimides in laminate construction. 

A preaccelerated, summer grade, laminating resin with excellent wettability, suitable for the fabrication of large structures, tanks and boats. Can also be used for the reinforced backing to acrylic baths. More economical than the general purpose PGL 322 PLT 232, but in comparison to those systems, also able to provide laminates of greater tensile flexural strength, as well as flexural modulus. 

Figure 4.6 Effect of glass content on tensile modulus and flexural modulus for a variety of glass-reinforced laminates (Arvesen).

Carbon-Fiber Composites. Cured laminates of phenoHc resins and carbon-fiber reinforcement provide superior flammabiHty resistance and thermal resistance compared to unsaturated polyester and epoxy. Table 15 shows the dependence of flexural strength and modulus on phenoHc—carbon-fiber composites at 30—40% phenoHc resin (91). These composites also exhibit long-term elevated temperature stabiHty up to 230°C. 

With respect to the laminates as a structural material, regardless of the type of reinforcement, there are known some behaviour characteristics during the mechanical loading of laminates. Composites with woven reinforcement demonstrate (Dauda et al. 2009) a linear relationship between stress and deformation. Whereas the reinforcement of laminates in the form braided reinforcement show a non-linear dependence is determined by an angle of orientation of the fibre bundles with respect to the axis of symmetry. The increase in flexural strength and modulus values affects the volume fraction of fibres in the composite volume, and the surface density of the strengthening. 

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