Sheet Molding Compound with highly aligned fiber reinforcement: An experimental investigation

This paper presents a method for aligning chopped glass fibers during SMC production on an SMC-line, using a vibrating gate to obtain a preferential fiber orientation in the semi-finished material. The vibrating gate consisted of multiple blades with varying height and relative distance, resulting in multiple slit configurations. Processing parameters of this test setup were varied in an experimental study to determine the effects on the resulting fiber orientation. Digital image analysis was used to quantify the degree of fiber orientation in the semi-finished material, and in the molded SMC plates produced thereof. In addition to that, tensile strength and modulus were characterized in dependance of load direction following DIN EN ISO 527. Material anisotropy was also characterized with a non-destructive test method using tensile discs. It was found that the chosen process approach was suitable to achieve a preferential fiber orientation, with the blade distance being the most influential parameter on fiber alignment. Highest fiber alignment results were achieved with a configuration with 5 mm relative distance between blades: (a) A fiber fraction of 45% was achieved within 0° ± 20°, (b) in the 0° orientation, tensile strength was doubled, and modulus was increased by 55% compared to a reference SMC with random fiber distribution.