Composites and fibres

The blast response of composite and fibre-metal laminate materials used in aerospace applications... 

Bouten P C P and Broer D J, Coating composition and fibre life time , Proc. SPIE, 1994, 2074, 59-64. 

Stmctures such as braided, tufted, felt, film, foam, laminated, bonded, stitched-through, net, embroidery, quilt and laced stmctures can also be formed. Textile composites and fibre-reinforced composites are another form of textile stmctures, consisting partly of textile materials (Corbman, 1983). 

Since the subject of this book is composites and fibres are usually added to resins to increase stiffness and strength, rather than deliberately to alter impact or fracture properties, it is not proposed to give further details of the impact performance of unreinforced polymers here. 

R. Moreton, Carbon Fibres Their Composites and Applications, Paper No. 12, The Plastics Institute, London, 1971. 

The properties of a foam are determined by the properties of the polymer, and by the relative density, p/p - the density of the foam (p) divided by that of the solid (p ) of which it is made. This plays the role of the volume fraction Vf of fibres in a composite, and all the equations for foam properties contain p/p. It can vary widely, from 0.5 for a dense foam to 0.005 for a particularly light one. 

Fig. 26.3. The molecular structure of a cell wall. It is a fibre-reinforced composite (cellulose fibres in o matrix of hemicellulose and lignin).

Epoxide resins reinforced with carbon and Aramid fibres have been used in small boats, where it is claimed that products of equal stiffness and more useable space may be produced with a 40% saving in weight over traditional polyester/ glass fibre composites. Aramid fibre-reinforced epoxide resins have been developed in the United States to replace steel helmets for military purposes. Printed circuit board bases also provide a substantial outlet for epoxide resins. One recent survey indicates that over one-quarter of epoxide resin production in Western Europe is used for this application. The laminates also find some use in chermical engineering plant and in tooling. 

Consider a composite with continuous aligned fibres as shown in Fig. 3.3. If the moduli of the matrix and fibres are and Ef respectively then the modulus of the composite may be determined as follows. 

It is also worthy of note that large values of Poisson s Ratio can occur in a laminate. In this case a peak value of over 1.5 is observed - something which would be impossible in an isotropic material. Large values of Poisson s Ratio are a characteristic of unidirectional fibre composites and arise due to the coupling effects between extension and shear which were referred to earlier. 

In a unidirectional Kevlar/epoxy composite the modular ratio is 20 and the epoxy occupies 60% of the volume. Calculate the modulus of the composite and the stresses in the fibres and the matrix when a stress of 50 MN/m is applied to the composite. The modulus of the epoxy is 6 GN(m. ... 

If the matrix in 3.7 was reinforced with the same volume fraction of glass but in the form of randomly oriented glass fibres rather than continuous filaments, what would be the tensile strength of the composite. The fibres are 15 mm long, have an aspect ratio of 1000 and produce a reinforcement efficiency of 0.25. The fibre strength is 2 GN/m and the shear strength of the interface is 4 MN/m". 

A pyrolysis technique was investigated as a method for the chemical recycling of glass fibre-reinforced unsaturated polyester SMC composites. The proeess yielded liquid products and gases and also a solid residue formed in the pyrolysis of glass fibres and fillers. The solid residue was used as a reinforeement/filler in unsaturated polyester BMC composites, and the influenee on mechanical properties was studied in comparison with BMC prepared entirely from virgin materials. 

On-line SFE-SFC-ELSD analysis of the textile and fibre finish components, butyl stearate/palmitate/myri-state, was reported [118]. Similarly, Kirschner et al. [119] used on-line SFE-pSFC for fibre finish analysis on-line SFE-SFC was also instrumental in the analysis of the total composite finish on a commercial textile thread [120]. 

Lanxide A process for making composites of metals with oxides. A molten metal reacts with an adjacent oxidant and is progressively drawn through its own oxidation product so as to yield a ceramic/metal composite. Fibres or other reinforcing materials can be placed in the path of the oxidation reaction and so incorporated in the final product. The Lanxide Corporation was founded in 1983 in Newark, DE, to exploit this invention. In 1990 it formed a joint venture with Du Pont to make electronic components by this process. Variations are Dimox (directed metal oxidation), for making ceramic metal composites, and Primex (pressureless infiltration by metal), for making metal matrix composites. 

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