Predicting mold flow for unsaturated polyester resin sheet molding compounds

• Published in: Polymer composites 1980-09, Vol.1 (1), p.14-23
• Main Authors: Silva-Nieto, R. J., Fisher, B. C., Birley, A. W.
• Format: Article
• Language: English
• ISSN: 0272-8397; 1548-0569
• DOI: 10.1002/pc.750010105

Improved products can be obtained from sheet molding compounds (SMC) if due regard is given to the geometry of the molding charge relative to the product shape. For example, it is possible to position designed charge shapes in the mold to produce moldings without weld‐lines and without substantially altering the initial fiber orientation of the SMC matrix. This paper describes theoretical and experimental work which has developed a charge shape calculation procedure for molding two‐dimensional SMC components weld‐line free without substantially altering the SMC‐matrix glass fiber orientation. The two main parts of the work are; (i) The theoretical development of a charge shape calculation procedure for molding symmetrical and unsymmetrical plaques. This includes a mathematical description of the compression flow process, which is used to determine flow front development from mold‐cavity pressure and velocity distributions. (ii) The results of experimental work which test the mathematical description of the compression flow process, and charge shape calculation procedure. These results include mold pressure measurements from an instrumented mold, fiber distribution and orientation measurements, and SMC‐material tensile strength properties.