Orientation of filler particles

How does the orientation of filler particles affect material properties ... 

Shear controlled orientation technology was developed to optimize plastic properties by orientation of filler particles. In this patented technology, the single feed is split into a plurality of feeds which can supply pressure to the mold cavity independent of the feed channel. Figure 7.3 shows feed arrangements. The shear is applied by a controlled movement of pistons which imposes microscopic shear. A perfect alignment of fibers can be obtained. 

We have shown that orientation of filler particles can affect many properties (sometimes in unexpected ways). The best orientation depends on the property which is to be optimized and on the materials in the application. Extensive use is being made of these means of improving properties. Many materials can be further improved by application of these principles. 

Orientation of filler particles is also important therefore warpage is influenced by processing conditions which tend to orient the filler such as rate of flow, temperature, ejection temperature, and material crystallization conditions. The current literature does not provide much information on this subject. 

Much of the treatment contained within this volume is limited by the assumptions that the adhesives, and usually the adherends, are linear elastic, homogenous, and isotropic. For bulk adhesives, the assumption of isotropy is usually justified, although instances do arise where preferred orientation of filler particles or crystalline regions can lead to anisotropic behavior. Common adherends such as fiber-reinforced composites, wood, and cold-drawn metals often exhibit anisotropic behavior that can significantly affect Joint behavior. 

Figure 23.6 Orientation of filler particles within injection-molded test bars.

The geometry and orientation of filler particles has a significant influence on the thermal conductivity of a composite material. Many of the theoretical treatments are valid for only specific types of filler partkks and composite constructions. The possible scenarios include spherical fiUers, irr ulaily shaped fillers, flakes (3-D random and random in-plat X short fibers (3-D random and random in-plane), long fibers (unidirectional and random in-plane), and continuous fibers (unidirectional and cross-ply laminated). Each of these scenerios needs to be addressed separately, and will be doiK so in the following sections. 

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