Monitoring local fiber volume fraction in preform lap joints using Hall‐effect sensors

Abstract This article describes the use of Hall‐effect sensors for monitoring local values of the fiber volume fraction in vacuum‐assisted resin transfer molding. Nonintrusive sensors mounted on the vacuum bag enable monitoring at a large number of points, under molding inserts and around geometrical features. Magnets can be mounted on the outer face of nonmetallic moulds. Low‐cost sensors can be discarded if damaged and the signal is unaffected by ambient conditions. The technique is demonstrated for lap‐jointed preforms made from two different reinforcements. All results presented in the article are validated using linear variable differential transducers. Although preform thickness is higher at superimposed lap joints, the fiber volume fraction is significantly larger in the joints. Interlaid continuous plies lead to a more reproducible behavior. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers