Design Corner

Sensors and actuators used in the engine compartment are being exposed to higher temperatures, more aggressive media and more extreme thermomechanical loads than ever before. These combined stresses are imposing requirements that increasingly exceed the capabilities of the polymers traditionally used to encapsulate and mount electronic components. In such cases, switching to engineering polymers that offer higher performance can provide a cost-effective solution.

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Plastic components, especially those in home appliances. sporting goods and automotive applications. are frequently subjected to dynamic loads, i.e. vibrations and impacts. Steady state vibrations, either sinusoidal or random, can cause deformations and stresses beyond that of comparable static loads, and require special approaches in design.

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The high tensile strength and toughness of glass reinforced Zytel® (GRZ) permit designers to match the load-bearing strength of die castings with relatively minor changes to cross sections and wall thicknesses.

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The failure of materials by rupture is a continuing concern of design engineers. Rupture, or fracture, can occur as the result of a load larger than the load-bearing capacity of a part, or can be caused by repeated applications of a smaller load.

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Welding techniques for assembling parts molded in DuPont engineering thermoplastics conventionally require an input of energy that results in heat. This heat causes a brief melting of material at the interface of two parts to be joined. Simultaneous application of pressure produces a strong, homogenous bond.

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Engineering plastics have been used for pressure vessel applications for a long time. Lighter bodies, ballcock valves, and spray paint containers (Figure 1) are just a few examples of successful developments in this area.

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Self-tapping screws provide an economical means of assembling components, especially where dissimilar materials must be joined together. They offer a particular advantage where occasional disassembly may be necessary for maintenance or repairs.

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The “ideal” plastic assembly would have all components joined right in the molding shop. Press or snap fitted together by operators at the machine, finished products would be ready for packaging and shipment.

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Today’s design engineers employ powerful methods to understand and predict the behavior of complex structures under defined loads. But even such well-known theoretical methods as Finite Element Analysis, the mathematical computer program to calculate deformations and stresses anywhere in a structural model, are really only starting points.

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