Kevlar 49-epoxy resin composite

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...

More recently, Wilczynski, Ward and Hine [24] have proposed an inverse calculation method where the elastic constants of a fibre can be estimated from fibre resin composite and the elastic constants of the resin. The method was confirmed by measurements on polyethylene/epoxy and carbon fibre/epoxy resin composites. It has been applied [25] to the determination of the elastic constants of a new organic fibre, poly 2,6-dimidazo[4,5-6 4 5 -e]pyridinylene l,4(2,5-dihydroxy)pheny-lene (PIPD). This fibre is a lyotropic liquid crystalline fibre with a very high Young s modulus of 285 GPa and a much higher tensile strength (5.21 GPa) and compressive strength (5OOMPa) than other polyaramid fibres such as Kevlar. 

The properties of resins, which are the weakest components in every composite, will be considered first. For epoxy resin, the effect of crosslinking as a correlation of chemical structure with physical data was studied. Many properties can be understood by the molecular anisotropy of binding forces. Strong covalent and weak van der Waals forces act along and transverse to the polymer chains, respectively. This molecular anisotropy also exists in fiber materials, such as Kevlar, which consists of strong, highly stretched polymer chains, which are weakly bonded together. 

Table 2.30 Shear Properties of Composites of Kevlar 49 Fiber in Epoxy Resins (8) ...

Important fiber materials are surface-treated glass, boron, graphite (carbon), and aromatic polyaramides (eg, DuPont s Kevlar). In most composites the reinforcement constitutes ca 65% of the final mass. Orientation of the fibers is important in establishing the properties of the laminate. Unidirectional, bidirectional, and random orientations are possible. The characteristics of the cured resin system are extremely important since it must transmit the applied stresses to each fiber. A critical region in a composite is the resin-fiber interface. The adhesive properties of epoxy resins make them especially suited for composite applications. 

Sheu G S and Shvu S S (1994) Surface modification of Kevlar 149 fibers by gas plasma treatment. Part II Improved interfacial adhesion to epoxy resin, J Adhes Sci Technol 8 1027-1042. de Lange P J, Akker P G, Maeder E, Gao S L, Prasithphol W and Young R J (2007) Controlled interfacial adhesion of Twaron aramid fibers in composites by the finish formulation. Compos Sci Technol 67 2027-2035. 

Notwithstanding the remarkable properties of materials such as Kevlar, modem engineers are constantly looking for improved performance. One of the most successful areas in this regard is the development of composites such materials are manufactured in such a way that the final material has superior properties to the sum of its constituents. For example, fibres of Kevlar, glass or carbon are used to reinforce epoxy resins. Increasingly developments are focusing on more sophisticated materials for example, poly (ether ether ketone) can replace epoxy as the... 

The results are for Kevlar 49 fibre composites prepared with an epoxy resin, Dow Chemicals DER 332, cured with an amine. The fibre volume loading was 65 v/o. 

Cryogenic properties of fibers and composites are given in Table 2. Most fiber-composite properties are governed by anisotropic features originating in the fiber arrangement and anisotropy and fiber-matrix interfacial bond. The fiber-matrix bond is discussed in refs. (36) and (39). In this article, the matrix materials discussed are epoxy resins, poljdmides, and polycarbonates and the fibers glass, carbon, and Kevlar, ie, aramid fibers. 

Fig. 8. Integral thermal contraction of epoxy resins, particulate, and UD fiber composites ys temperature. 6153, range of powder-filled epoxy WZ, range of fiber-glass composites nun, range of carbon-fiber composites range of Kevlar fiber composites liillllD, range...

Polymer-matrix composites for aerospace and transport are made by laying up glass, carbon or Kevlar fibres (Table 25.1) in an uncured mixture of resin and hardener. The resin cures, taking up the shape of the mould and bonding to the fibres. Many composites are based on epoxies, though there is now a trend to using the cheaper polyesters. 

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