Repairing defects in fibre-reinforced plastics more efficiently

Fibre-reinforced plastics (FRP) are widely used in the aeronautic and automobile industry, but the repair of components made from these composite materials is often less economically viable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fibre layer orientation with an innovative laser-based repair process.

Defects in FRP pieces may be production or operation related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools and repair process, and the possibility of automation.

By using laser scarfing and subsequent patch repair, FRP pieces can be repaired with appropriate fibre orientation. The damaged material is removed layer-by-layer. A precisely fitting replacement, a so called patch, is used to close the defective area. Afterwards, resin can be used to infiltrate and consolidate the new fibre layers and the repaired area becomes very strong. The challenge in laser scarfing is a precise, non-residual removal of the damaged fibre layers. This is made more difficult by the varying thickness of the composite layers.

An optical system for recognising the fibre orientation of the exposed material could provide a solution. An existing system technology from the Apodius GmbH, which is already used for the manufacturing of dry, semi-finished fibre products, is used as technical basis.

In combination with the scanner-based laser scarfing process from the LZH, the new fibre orientation measuring unit achieves a higher geometrical resolution than that of mechanical ablation processes.

The goal of the project partners is to repair defects in FRP components more cost-efficiently. Thus, the replacement of parts could be avoided. The project “Optical measurement of the fibre layer orientation for controlling a precise, laser-based FRP repair” is funded by the German Federal Ministry for Economic Affairs and Energy (BMWi) within the framework of the Central Innovation Program SME (ZIM) for a duration of two years.

Photo credit: http://www.colourbox.com. Material used in the preparation of this article has been drawn from idw – Informationsdienst Wissenschaft.

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