Aramid fiber reinforced polymer

Figure 8.2 shows a pull-off test on a masonry structure reinforced with aramid fiber-reinforced polymer (AFRP). The rupture in this test is due to the lack of adhesion to the substrate and this means that the fiber-reinforced polymer (FRP) does not work properly. Proper failure of the material as a result of a pull-off test would also cause the separation of part of the masonry support. 

Properties of p-aramid fiber reinforced polymer composites... 

Short fiber reinforcement of TPEs has recently opened up a new era in the field of polymer technology. Vajrasthira et al. [22] studied the fiber-matrix interactions in short aramid fiber-reinforced thermoplastic polyurethane (TPU) composites. Campbell and Goettler [23] reported the reinforcement of TPE matrix by Santoweb fibers, whereas Akhtar et al. [24] reported the reinforcement of a TPE matrix by short silk fiber. The reinforcement of thermoplastic co-polyester and TPU by short aramid fiber was reported by Watson and Prances [25]. Roy and coworkers [26-28] studied the rheological, hysteresis, mechanical, and dynamic mechanical behavior of short carbon fiber-filled styrene-isoprene-styrene (SIS) block copolymers and TPEs derived from NR and high-density polyethylene (HOPE) blends. 

Epoxy resins are by far the most widely used polymer matrices for advanced structural composites and, if carbon, glass, and aramid fiber reinforced epoxies... 

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. 

The use of fiber-reinforced polymer (FRP) composite materials in the reinforcement of concrete structures has shown important results. These interventions are based on the application of carbon fiber, glass, or aramid impregnated with thermosetting polymers. The effectiveness of these interventions is demonstrated both by extensive research in the laboratory and by applications to existing structures. 

In this subsection the physicochemical and mechanical properties of the most common p-aramid brands will be discussed. It is worth noting that mostly p-aramids are used for reinforcement of thermoset and thermoplastic polymer matrices where strength and stiffness are critical. However, in the case of elastomer-based composites where more important are the flame resistance, flexibility and the resistance to thermal, impulse and vibrational stresses, the m-aramid fiber reinforcement renders superior properties [3]. 

Klein N, Marom G and Wachtel E (1996) Microstructure of nylon 66 transcrystalline layers in carbon and aramid fiber reinforced composites. Polymer 37 .5493-5498. 

Of the three most common reinforcing fiber types used for polymer-reinforced composites (carbon, glass, and aramid), carbon fibers have the highest modulus of elasticity and strength in addition, they are the most expensive. Properties of these three (as well as other) fiber materials are compared in Table 16.4. Furthermore, carbon fiber-reinforced polymer composites have outstanding modulus- and strength-to-weight ratios. 

Glass, carbon, and the aramids are the most common fiber reinforcements incorporated into polymer matrices. Other fiber materials that are used to much lesser degrees are boron, silicon carbide, and aluminum oxide tensile moduli, tensile strengths, specific strengths, and specific moduli of these materials in fiber form are given in Table 16.4. Boron fiber-reinforced polymer composites have been used in military aircraft components, helicopter rotor blades, and sporting goods. Silicon carbide and aluminum oxide fibers are used in tennis rackets, circuit boards, military armor, and rocket nose cones. 

Aramid fibers, 13 372-373, 395 asbestos substitute, 3 314t chemical resistance of, 19 731t consumption of, 19 735t mechanical properties of, 13 376 properties of, 1.9 729-7301 as reinforcement materials, 26 756, 760 Aramid films/papers, properties of, 1.9 7331 Aramid polymer device, 16 1 Aramid products, economic aspects of,... 

Composite In polymer technology a combination of a polymeric matrix and a reinforcing fiber with properties that the component materials do not have. The most common matrix resins are unsaturated thermosetting polyesters and epoxies, and reinforcing fibers are glass, carbon, and aramid fibers. The reinforcing fibers may be continuous or discontinuous. Some matrix resins are thermoplastics. 

For a variety of technical reasons the development of aromatic polyamides was much slower in comparison. Commercially introduced in 1961, the aromatic polyamides have expanded the maximum temperature well above 200°C. High-tenacity, high-modulus polyamide fibers (aramid fibers) have provided new levels of properties ideally suited for tire reinforcement. More recently there has been considerable interest in some new aromatic glassy polymers, in thermoplastic polyamide elastomers, and in a variety of other novel materials. 

The additional chain orientation in the direction of the fiber long axis, obtained from the nematic self-ordering in the system, leads to a dramatic enhancement of the mechanical properties of the polymer. A number of aromatic polyamides have thus achieved commercial importance because of the very high tensile strengths and moduli of the fibers that can be spun from the nematic solutions. These have consequently become attractive alternatives to metal or carbon fiber for use in composites as reinforcing material. The most significant of these aramid fibers are ... 

Aramid fibers are widely used as reinforcing fibers in high performance composites. One disadvantage is the poor adhesion to the matrix materials. This arises from the lack of functional groups in the polymer. To overcome the lack of adhesion, the fibers are treated by so-called finish formulations, which is essentially a surface treatment. 

---