Internal structure of short glass fiber reinforced polyamide 66 injection moldings by acoustic velocity measurement

Internal structure of short glass fiber reinforced polyamide 66 injection moldings were investigated by optical microscopes, scanning electron microscopy, and acoustic velocity measurement. The apparent four phases could be found and they were classified by their crystallinity and fiber orientations from the observations of micrographs. Such structure could be seen in acoustic velocity map. The difference in acoustic velocity could express the difference in phases. Acoustic velocity measurement was carried out before and after static tensile test, and fracture due to stress concentration of core region could be well understood.