MICROSTRUCTURE OF LONG-FIBER AND SHORT-FIBER REINFORCED INJECTION MOLDED POLYAMIDE

The variation of fiber orientation and content within injection molded rectangular plates is investigated. Fiber orientation and volume fraction are measured using metallographic polishing and a newly developed image-analysis system; fiber weight-fractions are measured using an ashing method. Three different moldings are studied; two of the long-fiber compound Verton, molded at different injection speeds, and one of the short-fiber compound Maranyl. Microstructural regions are identified and characterized, and the flow mechanisms by which they are formed are discussed. The results show that the long fibers segregate extensively, whereas the short ones do not. The major differences between the two compounds are found in the core: the core of the long-fiber compound has a higher content and orientation of fibers than that of the short-fiber compound.