Laminate design

A workable theory behind why unsymmetric cross-ply laminates deform as they do has been developed by Hyer (who has extended these papers). Thus, a reasonable understanding of the deformation mechanics exists and can be used to design laminates with specified curvatures. 

Fibers are often regarded as the dominant constituents in a fiber-reinforced composite material. However, simple micromechanics analysis described in Section 7.3.5, Importance of Constituents, leads to the conclusion that fibers dominate only the fiber-direction modulus of a unidirectionally reinforced lamina. Of course, lamina properties in that direction have the potential to contribute the most to the strength and stiffness of a laminate. Thus, the fibers do play the dominant role in a properly designed laminate. Such a laminate must have fibers oriented in the various directions necessary to resist all possible loads. 

Lamination in ceramic extrusion is one of those themes most frequently debated in print. On the one hand it is obviously a practice-relevant subject, whereas on the other it offers a lot of freedom for imaginative inventors keen to design lamination-eradicating appliances of all kinds, as well as to theorizing apologists who believe in lamination-firee extrusion . 

In the frog Xenopus laevis, five lamins have been identified. These have been localized to the nuclear periphery and were designated lamins A, I, II, III, and IV (Benavente et al, 1985 Stick and Hausen, 1985 Benavente and Krohne, 1985 Schmidt et al, 1994 Schneider et al, 1995). 

When possible, design laminates from compatible noaterials. 

The process can be used to recover scrap or low quaUty resins by using them as the core layer, and using outer layers of virgin resins designed for the specific functional needs of the product such as sHp or gloss and appearance. The inner core may be a foamed resin with surface layers of supedor finish resins. Coextmded films often eliminate the need for cosdy lamination processes. 

The ASA (now ANSI) performance code for Safety Glazing Materials was revised in 1966 to incorporate these improvements in windshield constmction. The addition of test no. 26 requiring support of a 2.3-kg ball dropped from 3.7 m defined this level of improvement. It was based on a correlation estabUshed between 10-kg, instmmented, head-form impacts on windshields, on 0.6 x 0.9-m flat laminates, and the standard 0.3 x 0.3-m laminate with the 2.3-kg ball (28). Crash cases involving the two windshield interlayer types were matched for car impact speeds and were compared (29). The improved design produced fewer, less extensive, and less severe facial lacerations than those produced in the pre-1966 models. 

General-purpose type is a high pressure decorative laminate (HPDL) designed for both horizontal and vertical appHcations where appearance, durabiUty, resistance to stains, and resistance to heat up to 135°C (275°F) are requited. 

Miscellaneous Types. Various decorative effects have been developed which meet specific aesthetic requirements. These laminates may have special visual appeal, such as gloss finish, deeply embossed textures, and metallic surfaces. They are designed for specific installations and may not be suitable for all apphcations. For this reason, they are not included in these standards. Information concerning thein proper appHcation, properties, and care should be requested from the manufacturer. 

Pig. 2. (a) The cell mount design of the integrated PV array of Pigure 1, which uses laminated conductive and insulating layers on top of an aluminium substrate in a printed circuit board-type panel (7). The array produces 20 kW at 20°C ambient and 850 W/m direct sunlight, and measures 155 m. The lens is a molded acryUc Presnel lens parquet mounted on the front of the array stmcture. The PV panel is mounted on the back of the array stmcture and is... 

Butyl and Halobutyl Rubber. Butyl mbber is made by the polymerization of isobutylene a small amount of isoprene is added to provide sites for curing. It is designated HR because of these monomers. Halogenation of butyl mbber with bromine or chlorine increases the reaction rate for vulcanization and laminates or blends of halobutyl are feasible for production of mbber goods. It is estimated that of the - 100 million kg of butyl (UR) and halobutyl (HIIR) mbber in North America, over 90% is used in tire apphcations. The halogenated polymer is used in the innerliner of tubeless tires. Butyl mbber is used to make innertubes and curing bladders. The two major suppHers of butyl and halobutyl polymers in North America are Exxon and Bayer (see ELASTOLffiRS,SYNTHETIC-BUTYLrubber). 

The decorative plastic laminates widely used for countertops and cabinets are based on melamine—formaldehyde resin (see Laminates). Several layers of phenohc-saturated kraft paper are placed in a press and a sheet of a-ceUulose paper printed with the desired design and impregnated with melamine—formaldehyde resin is placed over them. Then a clear a-ceUulose sheet, similarly impregnated with the resin, is placed on top to form a clear, protective surface over the decorative sheet. The assembly is cured under heat and pressure up to 138°C and 10 MPa (1450 psi). A similar process is used to make wall paneling, but because the surfaces need not be as resistant to abrasion and wear, laminates for wall panels are cured under lower pressure, about 2 MPa (290 psi). 

Poly(phenylene sulfide) (PPS) is another semicrystalline polymer used in the composites industry. PPS-based composites are generally processed at 330°C and subsequently cooled rapidly in order to avoid excessive crystallisation and reduced toughness. The superior fire-retardant characteristics of PPS-based composites result in appHcations where fire resistance is an important design consideration. Laminated composites based on this material have shown poor resistance to transverse impact as a result of the poor adhesion of the fibers to the semicrystalline matrix. A PPS material more recently developed by Phillips Petroleum, AVTEL, has improved fiber—matrix interfacial properties, and promises, therefore, an enhanced resistance to transverse impact (see PoLYAffiRS containing sulfur). 

The steel of laminations plays a very significant role in determining the heating and the power factor of a motor. See Section 1.6.2A(iv). A better design with a judicious choice of flux density, steel of laminations and its thickness are essential design parameters for a motor to limit the core losses to a low level. 

---