MSU Technologies

Dual Mode Sensor for Non Destructive Testing of Composites

Executive Summary

Fiber reinforced composites are used in a wide variety of applications in the automotive, aerospace, boating and energy sectors. Testing the composites for defects is an important part of manufacturing quality control, however, this often requires the costly sampling and destructive testing of finished parts. While several technologies exist for non destructive testing, these devices are often limited to measuring one specific type of flaw. MSU and the US Dept of Army researchers have recently developed a new dual mode system that uses both eddy current testing (ECT) and capacitance imaging (CI). By combining both modes, the system can detect flaws such as fiber breakage or irregularities and interlayer delamination in-situ, without damaging or consuming parts.

Description of the Technology

This invention consists of a electronic circuitry and a unique sensor design which can be electronically switched between ECT and CI modes. In ECT mode, the system detects local changes in electrical conductivity which is indicative of fiber damage in conductive fiber reinforced polymers. In the CI mode, the hybrid sensor is sensitive to local changes in dielectric properties which are caused by matrix damage or interlayer delamination. A wide range of frequencies can be used (currently tested up to 2 MHz). Images from the scans can be visualized on a screen to determine the presence of undesirable defects. The system has been tested on multiple parts including by moving via an XYZ gantry over 3D printed fixtures. It has also been tested on sandwich with conductive honeycomb cores, thick CFRP (up to 25 mm) and aluminum.

Benefits

Synergistically combines inductive & capacitive sensing modalities in one probe & one scan
Non-contact inspection (no couplants needed
Uses both ECT and CI modes for more comprehensive defect measurement
Can be easily fabricated on a flexible substrate & integrated with robotic manipulators to scan complex parts
Advanced signal processing algorithms for reducing the effects of probe tilt and lift-off variations
Developed sensor optimization framework

Applications

Rapid NDE of versatile materials & parts: electrically conductive (metals, CFRP), electrically insulating (plastics, GFRP, AFRP), homogeneous/isotropic & composites
Surface & subsurface damage detection (e.g. cracks, corrosion, voids, interlaminar delamination, wavy fibers)
Inspection of metallic structures such as plates, wires or pipes coated with dielectric insulators
Testing of dissimilar material joints
Automotive, aerospace, boat hulls, wind turbines