Untersuchung und Verbesserung der Bindenahtfestigkeit von technischen Bauteilen aus kurzfaserverstär

FKM 2004
Booklet No. 283
Project No. 256

Abstract:

Seam lines are still an optical and/or mechanical problem in thermoplastic injection molded parts. However, this weakness mainly occurs in fiber-filled molded parts due to the processing-induced orientation of the fibers parallel to the weld line. This means that the fibers are often perpendicular to the main load direction at the same time. In practice, therefore, possibilities are sought to avoid weld lines altogether or to influence the properties in a targeted manner, for example by means of technological solutions. Such possibilities are offered by so-called special injection molding processes, such as push-pull or cascade injection molding.

The aim of the project was to investigate in particular possibilities for eliminating/reducing the influence of weld lines on strength. It was also intended to examine the extent to which the results from commercial mold filling simulation software match those from experiments.

The main results of the project are
- the proof that the cascade technique in particular is suitable for completely eliminating weld lines by means of targeted flow or at least reducing their influence on the strength by reorienting the fibers
- the generally good prediction of mold filling and resulting fiber orientation, especially in the core layer
- the limit of the simulation calculation with regard to a direct indication of the correct position and length of the weld line; this can only be concluded to a limited extent via the resulting fiber orientation

These findings enable the product and tool developer to consciously use and critically assess prediction methods. In addition, as a result of these observations, it is possible to derive options for eliminating or reducing the
weld line influence in practical components.

The objective of the project was achieved.