The application of a radio influence voltage test to the detection of voids in elastomers : J. Martin, Mater. Eval. May (1970), p. 116

Abstract

A DESCRIPTION IS PRESENTED OF HOW A SERIES OF NDT METHODS WERE EXAMINED IN ORDER TO OBTAIN A RELIABLE SYSTEM OF DETECTING VOIDS IN LARGE ELASTOMER STRUCTURES WHICH ARE BONDED TO METAL. THE TECHNIQUE CHOSEN, CALLED THE RADIO INFLUENCE VOLTAGE (RIV) METHOD, IS AN ADAPTATION OF A TEST USED ON HIGH VOLTAGE POWER INSULATION. IT MEASURES CERTAIN ELECTRICAL CHANGES THAT OCCUR WHEN AN ELECTRICAL STRESS IS APPLIED TO AN ELASTOMER IF THAT ELASTOMER HAS ENTRAPPED VOIDS. THE METHOD IS SHOWN TO BE CAPABLE OF DETECTING VOIDS RANGING FROM APPROXIMATELY 0.005-IN. DIAMETER TO 1/16-IN. DIAMETER IN A 1/8-IN.-THICK LAYER OF NEOPRENE. SIMILAR RESULTS WERE OBTAINED ON 1/4-IN. AND 3/8-IN. LAYERS OF NEOPRENE. THE TEST IS EFFECTIVE EVEN WHEN THE BUBBLES ARE AT A METAL INTERFACE AND IS NOT SENITIVE TO CURE STATE OF THE POLYMER. SINCE THE REQUIRED ELECTRICAL PROPERTIES ARE NOT VERY RESTRICTIVE, THE TEST APPEARS TO BE CAPABLE OF DETECTING SMALL VOIDS IN A WIDE RANGE OF NONMETALLIC MATERIALS. THERE ARE ALSO SOME INDICATIONS THAT THE METHOD MIGHT SERVE AS A BOND QUALITY TEST BECAUSE IN SEVERAL CASES, DEFECTIVE BONDS WERE DETECTED EVEN WHEN THE JOINT WAS FREE OF VOIDS. /AUTHOR/