Thermographic analysis of a long fiber–reinforced thermoplastic compression molding process.

Temperature gradients across tooling surfaces and within parts during the compression molding process represent a major contributor to warpage patterns. The main objective of the current study was to analyze the limitations of thermography as a method to be used for the measurement of part surface temperature. Comparisons performed against simulation and thermocouple data revealed that while thermography is a relatively accurate method, reflectivity and environmental radiation could cause errors of up to 8%. Nonetheless, since thermography data remains precise with respect to the relative temperature distribution, it was used for the assessment of the effect of compression molding process parameters on part ejection temperatures. In this regard, it was found that mold temperature has an overwhelming influence on final part temperature, whereas hold time has a less significant, but still measurable influence. Other parameters such as pressure, charge temperature, and charge orientation exhibited no practical significance. It was also found that parts exhibited strong temperature nonuniformities and gradients of nearly 25 °C within patterns that were largely consistent among parts. Given that this study also suggested that simulation yields reasonable temperature field predictions in compression molding, these results are expected to guide future warpage reduction efforts with possible effects on a wider adoption of composite components in automotive industry. [ABSTRACT FROM AUTHOR]