Laminate, laminates designation

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. 

Figure 7-1 Basic Questions of Laminated Piate Design...

One of the key elements in laminated composite structures design is the ability to tailor a laminate to suit the job at hand. Tailoring consists of the following steps. We want to design the constituents of the laminate, and those constituents include the basic building blocks of the individual laminae and as well how they are oriented within the laminate. We design those constituents to just barely meet (with an appropriate factor of safety) the specific requirements for, say, strength and stiffness. 

The purpose of this subsection is to familiarize the reader with some of the basic characteristics and problems of composite laminate joints. The specific design of a joint is much too complex for an introductory textbook such as this. The published state-of-the-art of laminate joint design is summarized in the Structural Design Guide for Advanced Composite Applications [7-5] and Military Handbook 17A, Plastics for Aerospace Vehicles, Part 1, Reinforced Plastics [7-6]. Further developments can be found in the technical literature and revisions of the two preceding references. 

The analytical tools to accomplish laminate design are at least twofold. First, the invariant laminate stiffness concepts developed by Tsai and Pagano [7-16 and 7-17] used to vary laminate stiffnesses. Second, structural optimization techniques as described by Schmit [7-12] can be used to provide a decision-making process for variation of iami-nate design parameters. This duo of techniques is particularly well suited to composite structures design because the simultaneous possibility and necessity to tailor the material to meet structural requirements exists to a degree not seen in isotropic materials. 

That is, the fundamental laminate design problem can be expressed as given the loading N, Ny, and N, find the laminate stacking sequence in Figure 7-51. That is, what are the laminae orientations 01, 02 03- nnany of each orientation are needed, i.e., what... 

The manner in which the laminate design is approached can be expressed in flow-chart form as in Figure 7-59. There, some initial laminate is arbitrarily selected to start the procedure. Then, the laminate load-deflection behavior is evaluated by use of the laminate strength analysis procedure described in Section 4.5. That evaluation is theoretical in nature. The next step is to evaluate the laminate fatigue life, and that evaluation can only be done experimentally, although progress is... 

A possible adjunct to the laminate design procedure is a specific laminate failure criterion that is based on the maximum strain criterion. In such a criterion, all lamina failure modes are ignored except for fiber failure. That is, matrix cracking is regarded as unimportant. The criterion is exercised by finding the strains in the fiber directions of each layer. When these strains exceed the fiber failure strain in a particular type of layer, then that layer is deemed to have failed. Obviously, more laminae of that fiber orientation are needed to successfully resist the applied load. That is, this criterion allows us to preserve the identity of the failing lamina or laminae so that more laminae of that type (fiber orientation) can be added to the laminate to achieve a positive margin of safety. 

Some of the essential attributes of the laminate design process with optimization concepts were described in general terms. The process is indeterminate, unlike that for a metal plate. An iterative procedure must be used to guide a design toward satisfaction of the design requirements. 

Factors affecting laminate design for maximum apparent fracture toughness. 

Compatible plastics can flow through a single manifold reducing any potential problem down-stream in the multimanifold. Combinations can be made to provide different laminated designs. However, the final exiting layer thickness distributions can be affected by the amount of die body deflection if the die is not properly designed to take the required pressure loads. Any deflection causing distortion influences the melt flow channels (Chapter 17). 

Continuous-Laminate Process. This process is to foam continuously between two sheets of facing material, employing a laminator (double-belt conveyor). The productivity of this process is the highest, i.e., the yield of raw material is very good, and a high-quality product can be produced. The selection of material, foaming machine and laminator design are very important factors in this process. Excellent quality products have been manufactured by this process in the United States, Western Europe, and Japan. 

Nucrel [DuPont]. TM for an ethylene-meth-acrylic acid copolymer resin available for use in conventional extrusion coating, coextrusion coating, and extrusion laminating equipment designed to process polyethylene resins. Higher melt flow index results in fewer resin leaks. 

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