Spray and deposition characteristics of unsaturated polyester resin applied for impregnating long fiber preform composites

Abstract Spray up is a method intensively applied for short fiber reinforced plastic (FRP) products manufacturing. The current study investigated the application of spray up for impregnation and manufacturing of long fiber FRP products, which can bring major advantages of minimized impregnation time and fewer product defects. Computational fluid dynamics (CFD) modeling was applied to investigate the spray and deposition characteristics of the viscous general‐purpose unsaturated polyester resin on a glass fiber preform. Validation of CFD results was done using phase Doppler anemometer and camera imaging techniques, and errors were calculated. Droplet velocity distributions 30 cm from the nozzle tip showed an average absolute percentage error of 4.3% and root mean square error value of 0.68 m/s, which are minimal. CFD and experimental values of sprayed resin area coverage (main area) after 4 s of spray were 17 and 16.3 cm in diameter, respectively; this is a relatively small error. Resin pool thickness on the target surface was variable, values predicted numerically. Non‐uniformity of pool thickness can be compensated by using appropriate compaction mechanisms. It is also possible to impregnate large size and complex shape products using multiple nozzles of proper arrangement.