Strength of composites

The compressive strength of composites is less than that in tension. Tills is because the fibres buckle or, more precisely, they kink - a sort of co-operative buckling, shown in Fig. 25.5. So wliile brittle ceramics are best in compression, composites are best in tension. 

Ran Y. Kim, personal communication, 8 April 1981. For additional information, see Ran Y. Kim, On the Off-Axis and Angle-Ply Strength of Composites, in Test Methods and Design Allowables for Fibrous Composites, C. C. Chamis (Editor), Dearborn, Michigan, 2-3 October 1979, ASTM STP 734, American Society for Testing and Materials, 1981, pp. 91-108 (reprinted with permission). 

Manson (72,) expanded the concept to the solid state by observing that the strength of composite materials also depended upon the acid-base interaction between continuous and dispersed phases. More directly, Vanderhoff et al. (21) addressed the issue of adhesion of polymeric materials to corroded steel. They synthesized eight corrosion products of iron, and used the interaction scheme developed by Fowkes and Manson first to characterize the iron corrosion products as Lewis acids or bases and then to select polymer vehicles for practical coating systems. Such results were employed to enhance the adhesion of epoxy systems to substrates which were predominantly iron oxide in nature. A good overview of these Issues was presented by Fowkes in 1983 (74). ... 

Chan W.S.. Rogers C. and Aker S. (1986). Improvement of edge delamination strength of composite laminates using adhesive layers. In Composite Materials Testing and Design, ASTM STP 893 (J.M. Whitney ed.). ASTM, Philadelphia, PA, 266-285,... 

T = ultimate tensile strength of composite, psi T0 = ultimate tensile strength of matrix compound W = elongation at break of composite, %... 

Effect of porosity on flexural strength of composites with code 1723 matrix (reproduced by permission of Am. Ceram. Soc. Bull.) . 

As well as producing these broadly beneficial effects, thermal microstresses can also degrade the strength of composites. The tensile components of stress can help in crack initiation. In a composite with a uniform distribution of particles, the tensile components act only over distances comparable with... 

Recently Nishijima et al. investigated the radiation effects of three-dimensional glass-fabric reinforced plastics (3DFRP) mentioned in the preceding section, since the interlaminar shear strength of composites was expected to be greatly enhanced by the presence of Z-axis reinforcement [78]. Two kinds of 3DFRP were newly developed and named as ZI-003 and ZI-005 of which the matrices were epoxy and BT resins, respectively [28]. The compressive tests... 

The addition of SiC whiskers to silicon nitride matrices resulted in only moderate increases in the fracture toughness a compared to monolithic materials. Fracture strengths of composite materials showed increases in some cases and slight decreases in others. Summaries of the variations in toughness and strength are given in Tables 2.3 and 2.4. The moderate increases in... 

Fig. 21 Evolution of the modulus and notched impact strength of composites based on PP (MFR 4 dgmin 1) and increasing amounts of calcium carbonate, CaCC>3. Data taken from Tjong [53]...

Result of all tests in Figure 2 shows that inereasing the amount of replacement form 10% to 40%, decrease the compressive strength of composite cements. However, the highest compressive strength has seen in rice husk ash with 10% replacement but by increasing the amount of replacement its strength decreases sharply in comparison with other composite cements. This principle is also seen in silica fume specimens. 

Almeida SFM, Nogueira Neto ZS. Effects of void content on the strength of composite laminates. Comp. Struct. 1994 28 139 8. 

FIGURE 24.5 Three-point bending strength of composite compacts synthesized atvarions temperatures and pH 9. 

If specimens are cured in the autoclave, the strength of composites including FRP powder drastically dropped to the level of water-cured specimens. 

Figure 6.17. Ratio of Raman peak intensities at 1355 and 1575 cm vs. interlaminar shear strength of composites containing carbon fibers of different origin. [Data from Tang L-G, Kardos J L, Polym. Composites, 18,No.l, 1997, 100-13.]...

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