In most cases today, the handling and draping of carbon-fiber-reinforced polymer for smaller aerospace parts is done manually. (It is more common for larger parts.) Manual processes can lead to variation and quality problems. Plus, after lay-up, the tooling has to be placed in an oven or autoclave for pre-forming or curing. This involves high investments for an oven or autoclave and leads to long process times.
With those drawbacks in mind, Premium Aerotec has developed an automated handling and draping system for CFRP material, as well as self-heating tooling for pre-forming and curing CFRP parts.
The robotic handling device uses vacuum cups for holding the CFRP material at the end effector. A special plastic foam was developed for the draping process. The foam is tailored to the different kinds of CFRP material (dry laminates or prepeg material) to be draped.
Premium Aerotec has validated the draping system for simple 3D-areas (e.g., reinforcements at the inner loft line of shells) and for complex 3-D areas (e.g., complex C-shape spars).
The combination of the automated draping system and self-heating tools can reduce energy consumption and process cycle time by 16% or more, according to the company. The reduction of energy consumption for these process steps can be about 75%. Overall investment costs can be cut “dramatically,” largely because the need for autoclaving equipment and energy use is eliminated. With self-heating tooling, heat is applied only where it is needed.
The self-heating tooling, developed with the rest of the system at the company’s plant in Varel, Germany, can be made of different materials to suit the intended application. The tooling is equipped with thermocouples to sense temperature.
As a first step in development of the self-heating tooling, a demonstrator consisting of a graphite base body and a CFRP-laminated cover plate was made. The heating device for both pre-forming and curing was integrated inside the cover plate. The deviation of the temperature within the tooling was 10°C at maximum in the relevant area for part curing.
Premium Aerotec plans show that its development is also applicable to larger tooling—about 4 m in width and 10 m in length.
This article is based on SAE technical paper 2009-01-3211 by Dr. Hilmar Apmann, Martin Deepen, and Thorsten Flessner, all of the Research & Development for Production Systems unit at Premium Aerotec GmbH.