OFDR-Based Integral Process Monitoring and SHM System for Composites Manufactured by Resin Infusion Under Flexible Tooling

Abstract

Composite materials are now widely established across many high-performance industries like aerospace. Increased use has shown they are able to outperform legacy materials when used correctly and maintained well. On the contrary, issues around susceptibility to impact damage in-service and high manufacturing costs have limited applications in other areas. Several SHM-technologies have been successfully used to address many of the in-service monitoring needs. The aim of this work is to build upon a proven SHM system based on fiber optic sensors and develop a complementing integral manufacturing process monitoring regime. Distributed fiber optic sensors based on Rayleigh Optical Backscattering Reflectometry (OBR) are utilized in this research to capture key characteristics over a large area with high spatial resolution. The OBR sensors can monitor the entirety of a product’s life and not just certain aspects of it, thus providing feedback in the manufacturing stage and enabling quality improvements. The presented work assesses OBR for its merit with regards to manufacturing monitoring. The focus lies on the most important factors in liquid resin infusion of a dry fiber bed. The OBR sensor was integrated into the woven fabric during the manufacturing process to provide vital information on the fabric compaction level and infusion parameters. Those factors have great influence on the quality of the manufactured component. In a second stage, several adverse processing conditions, typical for Resin Infusion were simulated and the system’s detection capability of such flaws is analyzed. The results obtained reliably inform the vacuum pressure level and detect manufacturing process errors with millimeter-level spatial resolution. With the added potential for real-time data streaming online parameter changes can be made based on the sensor readings. This confirms the aptitude of the chosen OFDR sensing method and provides the basis for a highly integrated Life-Cycle management system.