Composites unidirectional

The difference between the bounds defined by the simple models can be large, so that more advanced theories are needed to predict the transverse modulus of unidirectional composites from the constituent properties and fiber volume fractions (1). The Halpia-Tsai equations (50) provide one example of these advanced theories ia which the rule of mixtures expressions for the extensional modulus and Poisson s ratio are complemented by the equation... 

Fig. 3.7 Variation of longitudinal and transverse modulus in unidirectional composites...

Example 3.6 A unidirectional composite consisting of carbon fibres in a PEEK matrix has the fibres aligned at 25° to the loading axis. If the fibres and matrix have the properties indicated below, calculate Ex, Ey, Gxy, Vxy, and Vyx. 

In this Example the angle, 6, was set at 25°. Fig. 3.11 shows the variation of the moduli and Poisson s Ratio values for all angles between 0° and 90°. This gives an interesting overview of the performance of unidirectional composites when subjected to off-axis loading. 

Fig. 3.11 Variation of properties in unidirectional composite as a function of fibre angle...

Fig. 3.13 Variation in direct and shear strains for unidirectional composite loaded axially...

Example 3.10 If a moment of Af, = 100 Nm/m is applied to the unidirectional composite described in the previous Example, calculate the curvatures which will occur. Determine also the stress and strain distributions in the global and local (1-2) directions. 

Hong T. Hahn and Stephen W. Tsai, Nonlinear Elastic Behavior of Unidirectional Composite Laminae. Journal of Composite Materials, January 1973, pp. 102-118. 

J. M. Whitney, Elastic Moduli of Unidirectional Composites with Anisotropic Filaments, Journal of Composite Materials, April 1967, pp. 188-193. 

D. F. Adams and D. R. Doner, Transverse Normal Loading of a Unidirectional Composite, Journal of Composite Materisds, April 1967, pp. 152-164. 

R. L. Foye, An Evaluation of Various Engineering Estimates of the Transverse Properties of Unidirectional Composites, Proceedings of the 10th National Sympo-... 

Other researchers have substantially advanced the state of the art of fracture mechanics applied to composite materials. Tetelman [6-15] and Corten [6-16] discuss fracture mechanics from the point of view of micromechanics. Sih and Chen [6-17] treat the mixed-mode fracture problem for noncollinear crack propagation. Waddoups, Eisenmann, and Kaminski [6-18] and Konish, Swedlow, and Cruse [6-19] extend the concepts of fracture mechanics to laminates. Impact resistance of unidirectional composites is discussed by Chamis, Hanson, and Serafini [6-20]. They use strain energy and fracture strength concepts along with micromechanics to assess impact resistance in longitudinal, transverse, and shear modes. 

G. C. Sih and E. P. Chen, Fracture Analysis of Unidirectional Composites, Journal of Composite Materials, April 1973, pp. 230-244. 

Donald F. Adams, Inelastic Analysis of a Unidirectional Composite Subjected to Transverse Normal Loading, Journal of Corrposite Materials, July 1970, pp. 310-328. 

Tabie 6 Comparative Fiber and Unidirectional Composite Properties... 

Table 2. The values of the characteristic parameters of a series of E-glass fiber, epoxy resin unidirectional composites for various fiber volume contents t>f... 

The homogenization was also found [200] to be incredibly fast for both longitudinal and transverse overall elastic moduli of the transversely-random [201] unidirectional composite of parallel fibers. It was almost impossible to distinguish [200] the overall ensemble-average moduli calculated with 9 and 289 fibers in a disordered unit cell. 

Reinforce injected parts locally. A more lightweight part can be made by reinforcing it at specific spots with an insert of unidirectional composite manufactured, for example, by filament winding. 

Figure 5.21 displays the reinforcement of a bush with an inner unidirectional composite insert. The principle is the same for a bush with a self-lubricating insert. 

Table 6.36 displays basic property examples of glass mat thermoplastics (GMT) thermoplastic prepregs and glass or carbon reinforced unidirectional composites. 

The properties of unidirectional composites in the fibre direction can compete with those of current metals and alloys. The highest-performance engineering plastics compete with magnesium and aluminium alloys. 

Cui, W.C. and Wisnom, M.R. (1992). Contact finite element analysis of three- and four-point short beam bending of unidirectional composites. Composites Sci. Technol. 45, 323-334. 

Petit, P.H. (1969). A simplified method of determining the in-plane shear stress-strain response of unidirectional composites. In Composite Materials Testing and Design, ASTM STP 460, ASTM, Philadelphia, PA, pp. 83-93. 

Pindera, M.J., Choksi, G., Hidde, J.S. and Herakovich, C.T. (1987). A methodology for accurate shear characterization of unidirectional composites. J. Composites Mater. 21, 1164-1184. 

Rosen, B.W. (1972). A simple procedure for experimental determination of the longitudinal shear modulus of unidirectional composites. J. Composites Mater. 6, 552-554. 

Sims, D.F. (1973). In-plane shear stress-strain response of unidirectional composite materials. J. Composite Mater. 7, 124-128. 

Nairn J.A. (1990). Fracture mechanics of unidirectional composites. J. Reinf. Plast. Compo.sites9,91-101. 

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