The press moulding process is being applied extensively as the mass production technology for composite materials especially FRP. In this process, although ribs are installed to strengthen the products, they tend to reduce the strength of products by the formation of interface due to two symmetrical flows from the both sides of flat parts toward the rib part. This interface is called “Weld Line”.
The aim of this paper was to clarify the behavior of weld line. At first, the initiation and growth of weld line were observed by flow visualization experiments. Then, three point bending tests were carried out to evaluate the press moulded products containing the weld line. Furthermore, fracture surface was observed microscopically by using SEM. From the above experiments, the following results were obtained.
(1) The weld line initiated at the opposite surface of the rib part and grew into the rib.
(2) The weld line reduced the bending strength to the value less than that of the specimen made of only resin.
(3) No reinforcement existed across the weld line.
Nextly, the numerical procedure to understand the growing of weld line was performed by applying the initial flow analysis presented previously. The results indicated that the weld line in the case of wide rib differed from that in the case of narrow rib width.
