Glass-aramid composite

Composites. The history of phenoHc resin composites goes back to the early development of phenoHc materials, when wood flour, minerals, and colorants were combined with phenoHc resins to produce mol ding compounds. In later appHcations, resin varnishes were developed for kraft paper and textile fabrics to make decorative and industrial laminates. Although phenoHcs have been well characterized in glass-reinforced composites, new developments continue in this area, such as new systems for Hquid-injection molding (LIM) and sheet-molding compounds (SMC). More compHcated composite systems are based on aramid and graphite fibers. 

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. 

Figure 6.10. Glass, aramid and carbon fibre reinforced composites tensile modulus versus tensile strength examples...

Pi-Pregs (Porcher Industries), balanced or UD composites, are made of glass, aramid or carbon fibre reinforced thermoplastics (PPS, PEI,TPU, PA 12). 

The standard ASTM D2585 filament wound pressurized bottle test method utilizes a 0.15-m (5.75-in.)intemal diameter filament wound bottle as the test article. This standard test method (with variation in bottle sizes) has been used extensively by the rocket motor industry [47-50] to evaluate glass, aramid, and graphite fiber composite vessel performance. This test method has generally shown good results, but is a relatively expensive test method. Testing of one 0.5-m (20-in.) diameter bottle can cost up to 20K. Other disadvantages are ... 

Figures 9.19 and 9.20 present a survey of the mechanical properties of some (unidirectional) composites, in comparison with some other materials. In Figure 9.19 the values of modulus and strength are plotted as such, while in Figure 9.20 these values have been divided by the specific mass. From Figure 9.20 the enormous advantage of composites with respect to stiffness and strength per unit weight, in comparison to metals, is clearly visible. The modem carbon and aramide composites are superior to those based on glass fibres, for the specific stiffness even by a factor between 4 and 5.

Glass fiber composites are the most common type of composite. However, graphite, aramide, and other reinforcements are finding applications in demanding aerospace functions and in premium sporting equipment such as fishing rods, tennis rackets, and golf clubs. 

Also, fibers are controversial. In one currently used handbook, natural, inorganic fibers such as wollastonite or asbestos have been included among fillers whereas other fibers were included in a separate group with only three materials glass, aramid, and graphite. But, mixtures of fibrous and particulate materials are found in many composites today and various natural materials having fibrous structures are considered fillers in technical papers. Again our definition includes these examples. 

If concrete removal is not required or supplementary reinforcing bars cannot be used, external reinforcement can be applied. For instance, steel bars may be encased in a shotcrete layer or steel plates may be bonded onto the concrete surface. Recently, the use of steel plates has been substituted by fibre-reinforced plastics (F. R.P.), that are composite materials with glass, aramide or carbon fibres embedded in a polymeric matrix (usually an epoxy system). F. R.P. are available in the form of laminates or sheets that are bonded to the concrete surface using an epoxy adhesive [11]. They are typically used to improve the flexural and shear strength or to provide confinement to concrete subjected to compression. The... 

Advanced composites have been used most extensively in helicopters. Sikorsky s S-75 helicopter, for example, is about 25% composite by weight, mostly graphite-epoxy and aramid-epoxy composite materials. Composites are used in rotors, blades, and tail assemblies. Future military helicopters are likely to comprise up to 80% advanced composites by structural weight. Graphite-epoxy composites are likely to be used in the airframe, bulk-heads, tail bones, and vertical fins, while the less stiff glass-epoxy composites will be used in rotor systems. 

Glass, aramid and carbon fibres are the most commonly applied fibres in polymer-matrix composites. Further fibres composed of boron or basalt... 

Composite reinforcement Polyester, glass, natural cellulosics (e.g. hemp, flax) Glass Glass Glass, aramid, carbon... 

Aramid FRPs have excellent impact resistance, particularly to ballistic impact. On a weight basis they are superior to glass fibre composites, which themselves offer good ballistic impact resistance, but they are more expensive. 

Strength fibers can be reduced by hybridization, i.e., by designing composites reinforced with mixed HS-glass/carbon, HS-glass/aramid, or HS-glass/boron fibers. 

It should be noted, however, that the thermal and mechanical properties of vegetable fiber reinforced polymer composites are notoriously lower than those of similar composites reinforced with synthetic fibers (e.g., carbon, glass, aramid) [1, 2,12]. The above-mentioned techniques, i.e., fiber drying and surface treatment or the addition of a compatibilizer, are mostly not enough to adjust the properties of vegetable fiber reinforced polymers to the desired level. Moreover, even though these treatments enhance adhesion, there is some controversy in the literature about their effect on the mechanical properties of the fiber itself and even when a more pronoxmced gain is noticed after treatment, the improvement for the composite is often within the scatter of the results. In addition, the cost and environmental impact of some of these treatments, especially of those more elaborated, often prevent their industrial scale applications. 

M.V.de Souza, S.N. Monteiro and J.R.M. d Almeida, Effect of the shear and coupling elements of the Aij and Dij matrices on the impact behavior of glass, aramid and hybrid fabric composites. Compos. Struct. 76,345-351 (2006). 

The 3p-SBS of untreated aramid composites decreases with increasing V-. The absolute shear strength is much lower than for carbon or glass. This must be caused by the weak aramid-epoxy interface, since the SCF is very low for aramid in epoxy. On the assumption of a weak interface this decrease may also be explained by the rule of mixtures, with the exception of the strong fall at =80 %. This sharp decrease is a good indication that fracture occurs at the interface. 

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