Investigation of quality related process variables in pultrusion by correlation of numerical and experimental data with application of an inline data acquisition system

Abstract

The pultrusion process is an efficient technology for the continuous production of fiber reinforced polymers. While the process is industrially established for decades, the interactions between process parameters and material quality of pultruded profiles are – despite various studies – not fully understood yet. Due to the complexity of the process and the variety of materials, it is difficult to identify generic and quality related process relationships. Based on a novel multidisciplinary approach, this paper investigates the correlation between simulation data and experimental based process- and quality data. Therefore, a pultrusion-specific epoxy resin is characterized and modelled and thermo-chemical process simulations are performed. A for pultrusion unique inline quality assurance and data acquisition system was developed, built-up and applied during the production of a rectangular, glass-fiber reinforced profile. The analyzed data involves cure variables, die pressure, temperature, pull-speed and -force, ultrasonic data, surface waviness and roughness and void content. As main result, the position of gelation at the profile’s centerline in respect to the die length was determined as important criteria to maintain a sufficient material quality. Furthermore, a correlation between the die pressure and an insufficient degree of cure was identified. No significant influences of the process parameters on the material quality could be observed as long as the process stayed in a stable process window. This indicates that no severe quality losses have to be expected at higher production rates. The methods and results developed in this work are applicable for the implementation in an automated process control in pultrusion.