Automated Immersion Type Ultrasonic C-Scan Inspection of Triangular Thermoset Composite Grid Structures for Aerospace Applications

Composite grid architectures, also known as lattices, are a lightweight structural application of fiber-reinforced composite materials. These structures are manufactured by laying down unidirectional fiber-reinforced composite tapes in different principal directions, which overlap at intersection points, forming a grid. The unidirectional elements between intersections are described as ribs, whereas intersection points are names as nodes. While, grid-stiffened composite structures are well known, their application was rare due to the challenges of their complex manufacturing and inspection processes. This work focuses on developing a non-destructive inspection method for composite lattice structures for aerospace applications. Carbon fiber-reinforced thermoset composite triangular grid structures were inspected by ultrasonic immersion type automated C-Scan equipment. Composite lattice inspection calibration samples were developed by inserting different types of artificial defects between the sample prepreg layers during manufacturing. An inspection procedure was developed for these complex structural parts with the aid of these calibration samples. The sensitivity of the scanning process according to the defect size was defined for C-Scan setup.