FRP repair method to cost less thanks to laser processing

A laser-based method for repairing fibre-reinforced plastics (FRP) that’s more economical for manufacturers is being investigated in a new project conducted by Laser Zentrum Hannover (LZH) and automation firm Apodius.

The goal of the two-year ForLase project is to repair defects in FRP parts more cost efficiently, as at the moment it often costs less to replace the entire part than patching the damaged component.

The technique being developed combines an optical measurement device for determining fibre layer orientation from Apodius with laser scarfing – an ablation process – and patch repair.

Once the fibre layer orientation has been established, the damaged material is ablated with a laser layer by layer. A patch is then used to close the defective area. Afterwards, resin can be used to infiltrate and strengthen the new fibre layers.

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, which can differ across the entire part or just in local areas. While the optical systems from Apodius are already used for manufacturing dry, semi-finished fibre products, these fibre orientation measuring devices are being developed further in order to detect varying layer thicknesses.

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

‘Due to the speed of the image recognition process, the measurement data can be evaluated in real-time. Thus, the prerequisite for controlling the scarfing process can be fulfilled, and the goal of automating the process is much closer,’ explained Dr Peter Jäschke, head of the composite group at LZH. A further advantage of laser processing, as compared to conventional processing, is that the laser is force-, contact- and wear-free.

‘For the manufacturers, this [process] means saving time and costs. And the longer the lifetime of a component, the better the ecological balance and the resource efficiency is,’ said Dr Dietmar Kracht, executive director of LZH.

The project ‘Optical measurement of the fibre layer orientation for controlling a precise, laser-based FRP repair’ (ForLase) is funded by the German Federal Ministry for Economic Affairs and Energy (BMWi) within the framework of the Central Innovation Program SME (ZIM).

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Technology, Repair, Composites