Non-Contact Measurement of Level of Impregnation (LOI) for Aircraft Primary Structure Prepreg

Non-contact ultrasound can accurately measure prepreg level of impregnation (LOI) in through transmission.

This is accomplished by measuring the signal amplitude of an acoustic pulse, which is transmitted through a prepreg substrate.  Because the amplitude is extremely sensitive to porosity, this provides a very accurate measurement of prepreg LOI.

Ultran has extensive experience applying our technology for in-process LOI measurement of carbon fiber prepreg.  Our in-line inspection systems are deployed worldwide to suppliers of unidirectional primary structure aircraft prepreg.

Correlation of NCU Transmissivity to Prepreg LOI

Ultran conducted a small business innovation research project (SBIR) for the US Air Force Research Laboratory to establish an accurate method to measure prepreg LOI.

We measured hundreds of prepreg samples of varying LOI and analyzed the relationship between ultrasonic transmissivity and the level of impregnation.  The results demonstrate a clear and accurate ability to measure the level of impregnation for unidirectional carbon fiber prepreg using non-contact ultrasound.

Because NCU can operate continuously and non-destructively, it provides an advantageous method for quality control during and after production.

C-scan Images from Select Prepreg Samples