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Numerical Prediction of Fiber Orientation in Injection-molded Short-fiber/Thermoplastic Composite Parts with Experimental Validation

Nguyen Thi Thanh Binh ⁽¹⁾, Morioka Mizuki ⁽¹⁾, Yokoyama Atsushi ^(1)*, Hamanaka Senji ⁽²⁾, Yamashita Katsuhisa ⁽²⁾, Nonomura Chisato ⁽²⁾

⁽¹⁾ Kyoto Institute of Technology - Kyoto - Japan, ⁽²⁾ Toyobo Co.,Ltd - Shiga - Japan

This study deals with numerical prediction of the fiber orientation in the short-fiber reinforced thermoplastic composites manufactured by the injection molding process. During injection molding process of the short-fiber/thermoplastic composite, the fiber orientation is produced by the flow states and the fiber-fiber interaction. And the fiber orientation prediction has became one of the most important challenge since it controls the mechanical and the physical properties of the final injection-molded parts. Folgar and Tucker equation is the well known for modeling the fiber orientation in a concentrated suspension. Folgar and Tucker included into Jeffrey's equation a diffusive type of term by introducing a phenomenological coefficient to account for fiber-fiber interaction. A developed model for the fiber-fiber interaction resulting from the modified rotary diffusion term is proposed. For modeling the fiber interaction, the fiber dynamic simulation has been introduced in order to obtain a global fiber interaction coefficient, which is a sum function of the fiber volume concentration, aspect ratio and angular velocity. The short-glass fiber reinforced polyamide 6 (PA6) with the fiber weight concentration of 30%, 50%, 70% was produced by injection molding process. An experimental program has been carried out in which the fiber orientation distribution has been measured in 100 x 100 x 2 mm injection-molded plate and 100 x 80 x 2 mm injection-molded weld by analyzed with 3D X-ray computed tomography system XVA-160, and calculated by X-ray computed tomography imaging. Fiber orientation data is predicted by using the proposed fiber interaction model incorporated into a computer aided engineering simulation package C-Mold. The modifying rotary diffusion term of to the Folgar-Tucker equation to obtain the global interaction coefficient improved the model prediction of the fiber orientation. The numerical prediction shows a good agreement with experimental validation. And the fiber orientation in the injection-molded weld was investigated.