Unlike traditional pipe-repair "weld patch" or "steel patch" methods, vacuum-assisted, hot-work-free composite repair bonds carbon fiber cloth directly over the affected area to seal leaks and reinforce. Carbon fiber's thermal expansion coefficient is very close to steel, giving long service life. The technique applies to steel vessels and storage tanks, providing strength reinforcement, fatigue repair and buckling repair — including local surface defects.
Advantages Over Mechanical Repair
- High specific strength and modulus — minimal added weight after bonding
- Tailorable design — ply schedule customised to load and conditions
- Conforms to complex curvature — in-situ cure on shaped surfaces; preserves the original profile
- Lower stress concentration — bonding raises defect-zone stiffness and reduces crack-tip stress intensity; no new holes drilled
- Short cycle, low cost
- Minimal equipment — primarily a repair kit and a vacuum pump
- Hot-work free — safe and reliable
Critical Elements
Adhesive Selection
The adhesive arrests the crack. Match it to service load and environment: fatigue resistance, shear and peel strength, fluid and hygrothermal resistance. Two families: two-component adhesives (room-temperature cure) and film adhesives (heat-bonded cure).
Patch / Substrate Matching
The patch should cure at the lowest practical temperature, with thermal expansion matched to the host. Boron/epoxy is common abroad but costly; for industrial repair, carbon/epoxy — long used in aerospace — is more economical and suited to complex geometry.
Surface Preparation
Mechanical removal of oxidation and contaminants, or chemical deposition of a controlled oxide layer. Standard: grit-blast or grind to St3 followed by a silane coupling agent.
Vacuum-Assisted Cure
Pressure, temperature and time are controlled by a dedicated vacuum pump and matched consumables — continuous conditioning across the bondline.