Composite materials short-fibre

Polymer matrix composites (PMC) are used to increase the rather low stiffness or strength of polymers by adding stiffer or stronger fibres. If thermoplastics are used as matrix material, short fibres can be added to the granulate material that is subsequently softened by heating and processed, for example in injection moulding. If thermoset resins (duromers) are used, the fibres can be placed into the liquid resin before curing. 

A composite material for a car-repair kit consists of a random mixture of short glass fibres in a polyester matrix. Estimate the maximum toughness of the composite. You may assume that the volume fraction of glass is 30% the fibre diameter is 15 pm the fracture strength of the fibres is 1400 MPa and the shear strength of the matrix is 30 MPa. 

Tsai, S.W. and Hahn, H.T. Introduction to Composite Materials, Technomic Westport, CT (1980). Folkes, M.J. Short Fibre Reinforced Thermoplastics, Research Studies E ress, Somerset (1982). Mathews, F.L. and Rawlings, R.D. Composite Materials Engineering and Science, Chapman and Hall, London (1993). 

Reinforcements in the form of continuous fibres, short fibres, whiskers or particles are available commercially. Continuous ceramic fibres are very attractive as reinforcements in high-temperature structural materials. They provide high strength and elastic modulus with high temperature-resistant capability and are free from environmental attack. Ceramic reinforcement materials are divided into oxide and non-oxide categories, listed in Table 3.1. The chemical compositions of some commercially available oxide and non-oxide reinforcements are given in Table 3.2 and Table 3.3. 

S. T. Mileiko, Steady State Creep of a Composite Material with Short Fibres, Journal of Materials Science, 5, 254-261 (1970). 

The influence of external variables, i.e. testing and environmental conditions such as rate of loading, temperature and moisture, on fracture mechanisms and hence on fracture toughness in short fibre polymer composites is investigated as a function of fibre orientation with respect to the fracture plane. Unidirectionally oriented materials with different polymer matrix (polyamide 6.6 and polyoxymethylene) and different glass fibre content (15wt% and 30wt%) are examined. 

Short fibre polymer composites are being increasingly used as engineering materials because they provide mechanical properties superior to neat polymers and can be processed easily by the same fabrication methods, e.g. injection moulding. The mechanical properties of these materials are dependent on a complex combination of several internal variables, such as type of matrix, fibre-matrix interface, fibre content, fibre dimensions, fibre orientation, and external... 

Fara, S. and Pavan, A. Fracture toughness in short fibre composites analysis of fracture mechanisms in relation to fibre orientation in unidirectional materials to be submitted. 

A solid structural substance produced by a combination of two or more materials that retain their identities. Typically, one of the materials combined is the strengthening agent, the other being the matrix (a thermoset or a thermoplastic resin). The word composite is also used for systems that are reinforced (reinforced where cumulative properties are superior to the individual components) by addition of certain solid particles (i.e., short fibre composites - long fibre composites - continuous fibre composites). 

B. Heidenreich, R. Renz andW. Krenkel, Short Fibre Reinforced CMC Materials forHigh Performance Brakes, High Temperature Ceramic Matrix Composites (Eds. W. Krenkel, R. Naslain, H. Schneider), WILEY-VCH, Weinheim, Germany (2001), p. 809-815. 

Other toughening mechanisms are related to the debonding and pull-out of the inclusions during fracture. These mechanisms are especially effective in whisker and short-fibre reinforced glass composite materials [35]. 

A. R. Boccaccini, R. Liebald, W. Beier and K. K. Chawla, Fabrication, Mechanical Properties and Thermal Stability of a Novel Glass Matrix Composite Material Reinforced by Short Qxycaibide Fibres, J. Mat. Sci. 37, 4379-4384 (2002). 

The linear elastic stress analysis of a short fibre composite by the shear lag theory is due originally to H. L. Cox. The real composite (see Figure 6.32(a)) is assumed to deform in the vicinity of any particular fibre as if it were the model tem shown in Figure 6.32(b). In the model, the fibre (of diameter d) is surrounded 1 a cylinder of matrix of radius R, embedded in a homogeneous block of material which deforms as the composite as a... 

For each of the following short-fibre composite materials, tested in tension parallel to the fibres, predict the tensUe modulus. (Percentages given are fibre volume firactions.)... 

Ibarra L, Macias A, Palma E, Mechanical properties of composite materials consisting of short carbon fibre and thermoplastic elastomers, Kautschuk Gummi Kunstoffe, 48(3), 180-184, 1995. Jacobsen RL, Tritt TM, Guth JR, Ehrlich AC, Gillespie DJ, Carbon, 33(9), 1217-1221, 1995. Tibbetts GG, Doll GL, Gorkiewicz DW, Moleski JJ, Perry TA, Dasch CJ, Balogh MJ, Physical properties of vapour grown carbon fibres, Carbon, 31(7), 1039-1047, 1993. 

Compounds are short (/w 0.3 mm) or long (> 0.6 mm) fibre reinforced thermoplastic or thermoset polymeric materials, which are processed automatically (injection or compression moulding), have good (mechanical) properties (for automotive, electric and electronic applications) and are relatively cheap. Composites contain continuous fibres (rovings, fabrics or mats), usually combined with thermosets, have excellent mechanical (structural) properties, but are very expensive because lack of an industrial process (mainly used in aerospace and aircraft industry). 

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