Epoxy fiber composites

Fig. 15. The variation of the adhesion coefficient A = (ri, — t 2) for the three-term unfolding model and the exponent 2r for the two-term model of a series of E-glass-epoxy fiber composites, versus the fiber-volume content uf...

Williams, J. H.. Nayeb-Hashemi, H and Lee, S. S. (1979), Ultrasonic attenuation and velocity in AS 3501-6 graphite. epoxy fiber composite, NASA Report No. CR3I80. 

Composites. Various composite materials have evolved over the years as a significant class of high performance textile products. The prototype composite is carbon fiber with an epoxy resin matrix for stmctural akcraft components and other aerospace and military appHcations. Carbon fiber composites ate also used in various leisure and spotting items such as golf clubs, tennis rackets, and lightweight bicycle frames. However, other types of appHcations and composites ate also entering the marketplace. For example, short ceUulose fiber/mbbet composites ate used for hoses, belting, and pneumatic tire components. 

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. 

A variety of materials has been proposed to modify the properties of asphaltic binders to enhance the properties of the mix (112), including fillers and fibers to reinforce the asphalt—aggregate mixture (114), sulfur to strengthen or harden the binder (115,116), polymers (98,117—121), mbber (122), epoxy—resin composites (123), antistripping agents (124), metal complexes (125,126), and lime (127,128). AH of these additives serve to improve the properties of the binder and, ultimately, the properties of the asphalt—aggregate mix. 

Fig. 5. Interlaminar fracture toughness, for a number of thermosetting and thermoplastic composites (36,37). Open white bars represent glass-fiber composites shaded bars are for carbon fibers. The materials are A, polyester (unidirectional) B, vinyl ester (CSM = chopped strand mat) C, epoxy (R/BR1424) D, epoxy (T300/914) E, PPS F, PES and G, PEEK. To convert J/m to fdbf/in. multiply by 2100.

A number of amorphous thermoplastics are presently employed as matrices in long fiber composites, including polyethersulfone (PES), polysulfone (PSU), and polyetherimide (PEI). AH offer superior resistance to impact loading and higher interlaminar fracture toughnesses than do most epoxies. However, the amorphous nature of such polymers results in a lower solvent resistance, clearly a limitation if composites based on such polymers are to be used in aggressive environments. 

Using a method suggested by Saint-Flour and Papirer [100], Schultz and Lavielle obtained A// -values for the interaction of several vapors of differing donor numbers and acceptor numbers with various treated and untreated carbon fibers used in the preparation of carbon fiber-epoxy matrix composites. was expressed as ... 

Tsai conducted experiments to measure the various moduli of glass-fiber-epoxy-resin composite materials [3-1]. The glass fibers and epoxy resin had a Young s modulus and Poisson s ratio of 10.6 x 10 psi (73 GPa) and. 22 and. 5 x 10 psi (3.5 GPa) and. 35, respectively. 

Figure 11 Wohler chart of silanized and unsilanized jute reinforced epoxy-resin composites at different moisture contents (R = O.l f,est = 10 Hz fiber content = 40 vol%) [12].

Figure 14 Influence of fiber drying on the characteristic values of jute reinforced epoxy-resin composites [121.

Most carbon fiber composites are based mainly on thermosetting epoxy matrices. 

As soon as the Ar s were determined and the values of r s are found, the values of the adhesion coefficient A may be readily defined by using relation (27). The values of A s for the different fiber-volume contents studied are given in Table II for E-glass fiber-epoxy resin composites with different amounts of fillers, up to 70 percent 22 >. 

Fig. 18. The variation of the elastic moduli of mesophases, versus the polar distance r from the fiber-matrix boundary, for a series of E-glass-epoxy fiber reinforced composites...

A part, consisting of a carbon fiber composite tube, was initially adhered to the inside of a short titanium coupling by a silica-filled epoxy. The bond failed and a fluorinated mold release was believed to be the cause of the failure and was the purpose for this investigation. A sample of the epoxy (Sample A) and the part (Sample B) were submitted for X-ray photoelectron spectroscopy (XPS) to analyze for the presence of both fluorine and silicon. 

Fig. 2.5. Modulus data as a function of distance from the fiber surface of a carbon fiber-epoxy matrix composite which are measured from nanoindentation experiments. After Williams et al. (1990).

Fig. 2.7. Spectra of a glass fiber-epoxy matrix composite (a) before and (b) after hydrolysis. After Liao...

Fig. 2,10. Fiber strain and interfacial shear stress (IFSS) profiles along the fiber length for a heat-treated Kevlar 49 fiber-epoxy resin composite. At applied strains of (a) 0.60% (b) 1.90% and (c) 2,5%. After...

Fig. 3,4. Ln-Ln plot of fiber fragment length as a function of fiber stress (a) for Kevlar 29 fiber-epoxy matrix composite and (b) for a carbon fiber-epoxy matrix composite. Yabin et al. (1991).

Sandorf, 1980 Whitney, 1985 Whitney and Browning, 1985). According to the classical beam theory, the shear stress distribution along the thickness of the specimen is a parabolic function that is symmetrical about the neutral axis where it is at its maximum and decreases toward zero at the compressive and tensile faces. In reality, however, the stress field is dominated by the stress concentration near the loading nose, which completely destroys the parabolic shear distribution used to calculate the apparent ILSS, as illustrated in Fig 3.18. The stress concentration is even more pronounced with a smaller radius of the loading nose (Cui and Wisnom, 1992) and for non-linear materials displaying substantial plastic deformation, such as Kevlar fiber-epoxy matrix composites (Davidovitz et al., 1984 Fisher et al., 1986), which require an elasto-plastic analysis (Fisher and Marom, 1984) to interpret the experimental results properly. 

Fig. 3.27. Effect of the interface shear strength on mechanical properties of carbon fiber-epoxy matrix composites ( ) tran.sverse tensile strength (A) maximum transverse tensile strain (O) transverse tensile modiilns. After Madhukar and Drzal (1991),...

Netravali, A.N., Hcnstenburg, R.B., Phoenix, S.L. and Schwartz, P. (1989a). Interfacial shear strength studies using the single filament composite test, part I Experiments on graphite fibers in epoxy. Polym. Composites 10, 226-241. 

Scherf, J. and Wagner, H.D, (1992). Interpretation of fiber fragmentation in carbon/epoxy single fiber composites Possible fiber pre-tension effects. Polym. Eng. Sci. 32, 298-304. 

Interface properties of carbon fiber-epoxy matrix composites and Weibull parameters of carbon fibers"... 

Fig. 4.8. Variations of debond length, t, as a function of applied stress, for different coefficients of friction, p, for a XAIOO carbon fiber-epoxy matrix composite. After Zhou et al. (1995a, b).

---