Performance of additively manufactured composite mold with uniform fiber orientation

The spring-in phenomenon or reduced angle observed in a molded composite part with angled sides or an L-shape is commonly attributed to material anisotropy in the molded part and mismatched thermal expansion between the conventional metal tool and the molded part. This paper investigates the distortion and spring-in of a compression molded carbon fabric reinforced epoxy composite part with angled sides, using composite tooling that is made by extrusion deposition additive manufacturing (EDAM). The composite tooling was made from carbon fiber reinforced polyetherimide (ULTEM) by EDAM; as a result, material anisotropy existed in both tooling and molded part. In the present study, a uniform vertical orientation was used during the extrusion deposition printing of the mold, in order to promote heat transfer along the press closing direction. The thermomechanical properties were measured for the tooling material from EDAM-printed plaques and for the composite part material from molded plaques; the measured inputs were then used in simulation of mold deformation, residual stresses, and part distortion. The spring-in predicted for the part molded with the EDAM tool was 1.4°, which is close to the experimentally measured spring-in of 1.3°. The spring-in predicted for a similar molding cycle with the steel mold was much higher at 2.6°.