Experimental Study of Thickness Gradient Formation in the VARTM Process

ABSTRACT

Although the vacuum assisted resin transfer molding (VARTM) process has been the focus of much attention in the past several years, it is only recently that research tools have been developed to investigate fundamental process mechanisms associated with it. One area of concern for composites manufacturers is the ability to maintain dimensional tolerances throughout the process cycle. It has been well known that a thickness gradient forms during VARTM, leading to corresponding gradients in fiber volume fraction and the associated mechanical properties. In this work, the formation of these thickness gradients is investigated using an array of linear variable differential transformers (LVDTs) to monitor surface displacements during infusion. SMARTweave sensors are used to correlate resin flow with the surface displacements for infusions, using either a line resin source or point resin source. Software is used to display the surface displacements as a three-dimensional plot so that the entire part surface may be visualized during infusion.

Key Words:

• Gradient
• LVDT
• Resin transfer molding
• Surface displacement
• Thickness
• VARTM

ACKNOWLEDGMENTS

The authors would like to thank Dr. Melquiades Allende, Dr. James Campbell, and Mr. Pete Freese for their helpful contributions and ideas, and Mr. Doug Strand for his assistance with the experimental work. This work was funded by the U.S. Army Research Laboratory.