Why repair from the inside

A blade is held together by adhesive bondlines: at the leading edge, at the trailing edge, and between each shear web and the spar caps. In service these bondlines develop voids, cracks, disbonds and missing adhesive, and most of them are only visible from the inside.

Today there are two ways to repair them. A technician can enter the blade, but only reaches the part closest to the root. Or a rope team drills through the shell from the outside and injects adhesive, which perforates intact laminate, needs exterior access and leaves repaired holes in the aerodynamic surface. A crawler that already drives to the defect during the inspection is in the right place to fix it.

Where this sits on our roadmap

Detectra drives the length of the blade cavity and records the inside in 360° video, with every finding tied to its position along the blade. Repair solutions are on our roadmap: the same access to the defect, with equipment that fixes what the inspection found.

How in-cavity bondline repair works

  1. The robot drives through the blade cavity to the bondline defect and records its position along the blade.
  2. The defect is identified with the robot's cameras, by an operator watching the video or by automatic detection.
  3. If needed, the robot prepares the surface.
  4. The robot positions a nozzle at the defect and dispenses structural adhesive onto the bondline, to rebuild a missing fillet, or into it, to fill a crack or void. All of this happens from inside the cavity, without any opening in the shell from the outside.
  5. The bead is shaped and cured, and the result is checked on camera. Where the bead is short, the robot dispenses again.
  6. The repair is stored as a record: position, before and after images, adhesive type and quantity.

Variations

The approach covers all combinations of the following:

  • Platform: a repair module attached to the inspection crawler, a separate repair vehicle, or two coupled vehicles carrying supply and dispensing head. Battery powered, or fed through a tether from the root with adhesive, power and air.
  • Dispensing: two-component cartridges with a static mixer, single-component cartridges, or pumped meter-mix units. Several cartridges, or several adhesive types, per trip.
  • Nozzles: bead nozzles, fillet-shaped nozzles for web-to-cap corners, needle nozzles for injecting into cracks, and a sealing cup pressed around a crack for pressure injection, with a separate vent.
  • Quantity: set from the defect size seen by the robot's camera or depth sensing, and adjusted from the bead seen behind the nozzle.
  • Reach: the nozzle is positioned by driving the robot, on a linear slide, on an articulated arm, or on a telescoping mast that reaches upper bondlines from the lower shell.
  • Seam following: the head follows the bondline automatically while the robot drives, laying a continuous bead over several metres.
  • Surface preparation: brushing, vacuum, abrasion, solvent wipe, plasma treatment or primer.
  • Adhesives: epoxy, polyurethane and methacrylate structural adhesives, UV-curing adhesives, filled or fibre-reinforced pastes, and low-viscosity injection resins. The adhesive may be heated to control viscosity.
  • Curing: at ambient temperature, or accelerated by the robot with an IR lamp, a heated shoe, warm air or UV light.
  • Position: odometry, radio or visual markers, or structural landmarks such as the web stations.
  • Control: teleoperation, operator-marked defects that the robot then repairs, or automatic repair with a human confirming before dispensing.
  • Other materials and structures: sealants, coatings and adhesive-backed reinforcement patches applied the same way, and bondlines in other hollow composite structures such as aircraft wings, boat hulls and tanks.

We describe this openly so the approach stays available to the industry.