EVOLUTION OF THE 3-DIMENSIONAL ORIENTATION DISTRIBUTION OF GLASS-FIBERS IN INJECTED ISOTACTIC POLYPROPYLENE

The mechanical properties of fiber reinforced thermoplastics depend on the characteristics of the fibers, such as their three-dimensional or ientation distribution, which is the result of the processing conditio ns and of the initial products before mixing. Different composites wer e obtained by injection of reinforced isotactic polypropylene containi ng 30 wt% fibers. Different size distributions of fibers were investig ated. Their average lengths range from 60 to 470 mu m. Specific new to ols were developed by combining microscopy and image analysis to deter mine the microtextural characteristics of the fibers, such as their si ze distribution or their orientation in the matrix. Our technique allo ws the following of the size distribution evolution of the fibers as t he composite is processed. The three-dimensional orientation of the fi ber is established using the in-plane angle and the angle of inclinati on. The evolution of the three-dimensional orientation distribution is studied in the sample, by differentiating central and border behavior and also as a function of fiber size. It is concluded that the coupli ng of scanning electronic microscopy with image analysis is an interes ting technique that allows the 3-D orientation of the fibers to be det ermined. This technique is validated by showing that the results obtai ned agree with those that other authors obtained on comparable materia ls.