Epoxy/epoxies matrix

One more application area is composite materials where one wants to investigate the 3D structure and/or reaction to external influences. Fig.3a shows a shadow image of a block of composite material. It consists of an epoxy matrix with glass fibers. The reconstructed cross-sections, shown in Fig.3b, clearly show the fiber displacement inside the matrix. The sample can be loaded in situ to investigate the reaction of matrix and fibers to external strain. Also absorption and transmission by liquids can be visualized directly in three-dimensions. This method has been applied to the study of oil absorption in plastic granules and water collection inside artificial plant grounds. 

Piezocomposite transducers are an advancement of piezoelectric ceramics. Instead of the classic piezoceramic material, a compound of polymer and piezoceramic is used for the composite element to improve specific properties. The 1-3 structure, which is nowadays mostly used as transducer material, refers to parallel ceramic rods incorporated in an epoxy-resin matrix (see Fig. 1). 

In Figure 5.24 the predicted direct stress distributions for a glass-filled epoxy resin under unconstrained conditions for both pha.ses are shown. The material parameters used in this calculation are elasticity modulus and Poisson s ratio of (3.01 GPa, 0.35) for the epoxy matrix and (76.0 GPa, 0.21) for glass spheres, respectively. According to this result the position of maximum stress concentration is almost directly above the pole of the spherical particle. Therefore for a... 

Composites. Various composite materials have evolved over the years as a significant class of high performance textile products. The prototype composite is carbon fiber with an epoxy resin matrix for stmctural akcraft components and other aerospace and military appHcations. Carbon fiber composites ate also used in various leisure and spotting items such as golf clubs, tennis rackets, and lightweight bicycle frames. However, other types of appHcations and composites ate also entering the marketplace. For example, short ceUulose fiber/mbbet composites ate used for hoses, belting, and pneumatic tire components. 

Thus the addition of the stiff carbon fibers has a very great effect in stiffening the epoxy matrix. Eor the commonly used fiber volume fraction of 0.6 the unidirectional carbon—epoxy lamina has a predicted extensional stiffness E = 145 GPa (2.1 x 10 psi)-... 

Table 2. Structure and Properties of Aromatic Diamines and Acid Anhydrides Used in Epoxy-Matrix Resins...

Fig. 2. Epoxy matrix resius for advanced composites (a) TACTIX 558 (Courtesy of The Dow Chemical Company), (b) EPON HPT Resia 1071 (Courtesy...

The use of elastomeric modifiers for toughening thermoset resias generally results ia lowering the glass transition temperature, modulus, and strength of the modified system. More recendy, ductile engineering thermoplastics and functional thermoplastic oligomers have been used as modifiers for epoxy matrix resias and other thermosets (12). 

Using a method suggested by Saint-Flour and Papirer [100], Schultz and Lavielle obtained A// -values for the interaction of several vapors of differing donor numbers and acceptor numbers with various treated and untreated carbon fibers used in the preparation of carbon fiber-epoxy matrix composites. was expressed as ... 

Flexibilized epoxy resins are important structural adhesives [69]. Liquid functionally terminated nitrile rubbers are excellent flexibilizing agents for epoxy resins. This liquid nitrile rubber can be reacted into the epoxy matrix if it contains carboxylated terminated functionalities or by adding an amine terminated rubber. The main effects produced by addition of liquid nitrile rubber in epoxy formulations is the increase in T-peel strength and in low-temperature lap shear strength, without reducing the elevated temperature lap shear. 

Example 3.1 The density of a composite made from unidirectional glass fibres in an epoxy matrix is 1950 kg/m. If the densities of the glass and epoxy... 

A hybrid composite material is made up of 20% HS carbon fibres by weight and 30% E-glass fibres by weight in an epoxy matrix. If the density of the epoxy is 1300 kg/m and the data in Fig. 3.2 may be used for the fibres, calculate the density of the composite. 

Figure 3-53 Photoelastic Stress Patterns for Three E-glass Fibers Embedded in an Epoxy Matrix (Courtesy of Materials Sciences Corporation)...

C. E. Browning, G. E. Husman, and J. M. Whitney, Moisture Effects In Epoxy Matrix ComposHos, in Composite Materials Testing and Design (Fourth Conference), J. 

The epoxy matrix was filled with iron particles of average diameter df = 150 pm at a volume fraction uf = 0.05. The mechanical and thermal behaviour of the particulate composite was studied in Ref. 8), which gave the following values ... 

Thermal decomposition of the matrix material offers a simple way of recovering the relatively expensive reinforcing fibres from a fibre-reinforced laminate. The epoxy resin matrix was made to decompose by thermal treatment in air or nitrogen, this treatment allowing the carbon fibres to be recovered without damage. 

Liquid rubbers In order to improve the flexibihty of short glass fiber-reinforced epoxy composites, Kaynak et al. [53] modified the epoxy resin matrix with hydroxyl-terminated polybutadiene (HTPB) liquid mbber. A silane coupling agent was also used to improve the interfacial adhesion between glass fibers and epoxy matrix. However, Humpidge et al. [54] reported some unique processing problems for the resulting pasty mixmres when short textile fibers were incorporated in a hquid mbber medium. 

To assess the effect of elastomer degradation on composite performance, additional composites were fabricated with the same 121°C cure epoxy without any addition of the elastomer (211. The expansion behavior of the modified epoxy composite was similar to the toughened material. For electron doses less than 10 rads the CTE of the toughened and untoughened composites were essentially the same which suggests that the epoxy matrix and not the elastomeric component controls the thermal expansion behavior. 

It is found that the diffusion of the tributyltin species in the matrix is the rate limiting factor the highly crosslinked epoxy matrix offers great resistance for the diffusion of the large molecule. 

Nanocarbon composites can be broadly divided into three kinds, each with some possible subdivisions. Examples of these composites and their schematic representations are presented in Fig. 8.1. The first type corresponds to composites where the nanocarbon is used as a filler added to a polymer matrix analogous, for example, to rubber reinforced with carbon black (CB). The second consists of hierarchical composites with both macroscopic fibers and nanocarbon in a polymer, such as a carbon fiber laminate with CNTs dispersed in the epoxy matrix. The third type is macroscopic fibers based... 

CNT fibres/epoxy matrix (Zilatela etat.) CNT sheets/BMI matrix (Wanget at.) a CNT sheets/RTM matrix (Cheng etat.) t CNT sheets/PVA matrix (Liuet at.)... 

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