Caul plates are smooth metal plates, free of surface defects, the same size and shape as a composite lay-up, used immediately in contact with the lay-up during the curing process. They transmit normal pressure and temperature, and provide a smooth surface on the finished laminate. Used in conjunction with heat blankets for composite repair, caul plates prevent the heater blanket wires from making impressions in the repair. They provide a smoother, more aerodynamic surface and allow for more uniform distribution of heat. They also enable placement of thermocouples closer to the center of the repair.
Caul plates can be difficult to form to complex contours. Also, metal caul plates can cause thermocouple calibration problems. One solution to this problem is to use flashbreaker tape. Silicone rubber caul plates can act as insulators, if thick enough to prevent thermocouple mark-off.
For complex shapes, repair tooling is sometimes required. Repair plies can be laid up and debulked in the repair tool, or even partially cured (a process known as “staging”). The repairs can then be bonded to the original structure. This is not usually practical for quick field repairs, but is more useful for heavy maintenance type of repairs performed in a dedicated facility with specific repair equipment.
Published courtesy of Abaris Training Resources, Inc