Over-reinforced

Plastic settlement A Over reinforcement Deep sections Eccess bleeding Rapid early drying conditions 10 min to 3 h... 

F Over reinforcement R.C. slabs Rapid early drying, steel near surface ... 

Increase cover over reinforcement Decrease water/ cementitious ratio... 

Compression failure is the most desirable of the above failure modes. This failure mode is less abrupt than tension failure, and is similar to the failure of an over-reinforced section when using steel reinforcement. Tension failure is less desirable, since tensile rupture of FRP reinforcement will occur with less warning. Tension failure will occur when the reinforcement ratio is below the balanced reinforcement ratio for the section. This failure mode is permissible with certain safeguards. 

Grating Equation. The light incident on each groove is diffracted or spread out over a range of angles, and in certain directions reinforcement or constructive interference occurs, as stated in the grating formula ... 

Cera.micA.bla.tors, Several types of subliming or melting ceramic ablators have been used or considered for use in dielectric appHcations particularly with quartz or boron nitride [10043-11 -5] fiber reinforcements to form a nonconductive char. Fused siHca is available in both nonporous (optically transparent) and porous (sHp cast) forms. Ford Aerospace manufactures a 3D siHca-fiber-reinforced composite densified with coUoidal siHca (37). The material, designated AS-3DX, demonstrates improved mechanical toughness compared to monolithic ceramics. Other dielectric ceramic composites have been used with performance improvements over monolithic ceramics (see COMPOSITE MATERIALS, CERAMIC MATRIX). 

Nylon-6. Nylon-6—clay nanometer composites using montmorillonite clay intercalated with 12-aminolauric acid have been produced (37,38). When mixed with S-caprolactam and polymerized at 100°C for 30 min, a nylon clay—hybrid (NCH) was produced. Transmission electron microscopy (tern) and x-ray diffraction of the NCH confirm both the intercalation and molecular level of mixing between the two phases. The benefits of such materials over ordinary nylon-6 or nonmolecularly mixed, clay-reinforced nylon-6 include increased heat distortion temperature, elastic modulus, tensile strength, and dynamic elastic modulus throughout the —150 to 250°C temperature range. 

During the press operation, which is actually a form of compression mol ding, the resin-treated laminate pHes are heated under pressure and the resins cured. The initial heating phases cause the resin to melt and flow into voids in the reinforcing ply and bond the individual pHes together. The appHed heat simultaneously causes the resin to polymerize and eventually to cross-link or gel. Therefore, resin viscosity reaches a minimum during the press cycle. This is the point at which the curing process becomes dominant over the melt flow process. Dynamic mechanical and dielectric analyses (11) are excellent tools for study of this behavior. 

Fig. 7. Schematic of a self-contained plasma processing unit designed to continuously plasma-treat and impregnate with resin, reinforcing fibers for enhanced composite strength. The unit can also be used to plasma-treat wires to be coated or treated for improved adhesion. Throughput speeds of over...

The hand lay-up or spray-up process, used universally for the production of laminar composites incorporating glass fiber reinforcement, is most efficient for the manufacture of large parts, such as boats, bathtubs, tanks, architectural shapes, and recreational accessories. Resins intended for spray-up processes are usually modified with thixotropic additives, such as fumed siHca (1%), to reduce the risk of drainage when appHed over large vertical mold surfaces. Molds are also made from ERP for short-mn products usually surfaced with a tooling gel coat to provide consistent surface quaHty and appearance. 

Carbon Black. This is the principal reinforcing filler used in mbber. Carbon black is made by three processes the furnace process, the thermal process, and the channel process. Over 97% of black is made by the furnace process (see Carbon, carbon black). 

Reinforcing Fillers. Carbon black is by far the most heavily used reinforcing filler for tire compounds. Annual tire usage of all grades of carbon black is estimated to be over three million metric tons aimuaHy. 

DynaWave equipment is typicaUy smaller than conventional equipment and is usuaUy made of fiber glass reinforced plastic (ERP) at considerable capital savings over conventional materials. DynaWave is now in use at a number of plants worldwide. 

---