New Optimized Method to Recycle CFRP Composites While Maintaining Strength

 Researchers from the University of Sydney’s School of Civil Engineering have developed an optimized method for recycling CFRP composites while maintaining 90 percent of their original strength.

Loss of Properties in Recycled Products

Until now, it has been difficult to continuously recycle products made of carbon fibers. Given that most recycling involves shredding, cutting or grinding, fibers are worn out, decreasing a future product’s viability.

“Globally and in Australia there has been a march towards better recycling processes, however there is often the belief that a material can be recycled an infinite number of times – this simply isn’t the case. Most recycling processes diminish mechanical or physical properties of materials,” said the study’s lead researcher Dr Ali Hadigheh.

This presents a huge challenge and threat to the environment, as it has led to the production of virgin carbon fibre which contributes significantly to greenhouse gas emissions.

Cost-effective Method for Recycling Carbon Fiber

To combat this issue and to support a true circular economy, scientists have developed an efficient and cost-effective method for recycling carbon fiber, which is present in tablets through to BMWs.

Scientists used a two phased, optimized process. The first step is called pyrolysis which breaks down a material using heat, but significantly chars the materials which prevents it from developing a good bond with a resin matrix. The second process, oxidation, uses high temperature to remove this char.

Pyrolysis and oxidation alone are not enough to preserve carbon fibers and these processes have existed for some time already. To ensure a high-quality recovery and economic efficiency, thermal decomposition of CFRPs need to be guided by analyzing the energy required to initiate a chemical reaction in the composite, and separate carbon fibers from the surrounding resin matrix.

Specific Parameters for Successful Method

“What makes our method so successful is that we have added specific parameters – such as temperature, heating rate, atmosphere or time spent being oxidized and heated – that preserve the functionality of carbon fiber.”

“We embarked on the project with the aim of producing high grade, low-cost structural materials made from recycled carbon fiber composites, for use in industries from aerospace and automotive through to sporting goods and renewable energy and construction.”

Source: University of Sydney