Common Laminate Definitions

we need a common, unambiguous manner of writing how a laminate is specified to be laid-up, i.e., stacking-sequence notation. Then, quasi-isotropic, balanced, and hybrid laminates are defined. 

The term quasi-isotropic iaminate is used to describe laminates that have isotropic extensionai stiffnesses (the same in all directions in the plane of the laminate). As background to the definition, recall that the term isotropy is a material property whereas laminate stiffnesses are a function of both material properties and geometry. Note also that the prefix quasi means in a sense or manner. Thus, a quasi-isotropic laminate must mean a laminate that, in some sense, appears isotropic, but is not actually isotropic in all senses. In this case, a quasi-isotropic 

Although the word balanced is ambiguous and not definitive, the common meaning for a balanced laminate is a laminate in which all equal-thickness laminae at angles 0 other than 0° and 90° to the reference axis occur only in 0 pairs. The individual -n O and - 0 layers are not necessarily adjacent to each other. Note also that balanced laminates are required to be symmetric about the laminate middle surface, so there must be two + Q laminae and two - 0 laminae for each 0 pair. The behavioral characteristics of a balanced laminate are that shear- 

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Reinforced plastics (RPs) hold a special place in the design and manufacturing industry because they are unique materials (Figs. 6-11 and 6-12). During the 1940s, RPs (or low-pressure laminates, as they were then commonly known) was easy to identify. The basic definition then, as now, is simply that of a plastic reinforced with either a fibrous or nonfibrous material. TSs such as polyester (Table 6-19) and E-glass fiber dominated and still dominates the field. Also used are epoxies. 

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