Reviewing Thermoplastic Processing

Trelleborg

Reviewing Thermoplastic Processing

Thermoplastic composites are often cited for their benefits over thermoset materials. Improved performance after impact, specific energy absorption, strength, environmental resistance, and higher operating temperature are just some of the highlights.

However, due to the lack of inherent “tackiness” to the material, it has proven challenging to process. To manually lay up thermoplastics, it is required that each ply is tacked to the previous one using an ultra-sonic welder or a tool resembling a heating iron to melt material in a small area. A heated press or a high temperature autoclave is then needed to consolidate the laminate. This time and labor-intensive process has been one of the reasons why thermoplastic parts have been held back from many applications.

Automated Fiber Placement
When you break it down, thermoplastic processing is a tradeoff among time, temperature, and pressure. Modifying any one of these variables affects the magnitude needed for the other two. Our Automated Fiber Placement machines apply enough heat and pressure to the raw material that very little time is required to produce a laminate that is fully consolidated as it is being laid down. This process is known as in-situ consolidation.

The in-situ process offers a wide range of benefits, one of the most significant being that it eliminates the need for a secondary process such as a heated press, an autoclave, or an oven cure. The equipment for these secondary processes represents a substantial investment from the company utilizing them, especially when they are designed around processing thermoplastics. Removing the need for such equipment reduces project costs and saves company resources.

Additionally, removing secondary processes comes with the added benefit of improved throughput for many applications. While in-situ processing is slower than thermoplastic pre-forming (due to the need to balance the time, temperature, and pressure ratio), the net benefit of cutting out secondary steps results in faster production times.

Creating Cobonded Parts
A complex composite structure involving stiffeners can reap additional benefits from this process. If thermoplastic (or any other melt miscible material) stiffeners are inserted into the fiber placement tool, then as the material is fiber placed, it will bond to the stiffeners. This process is known as cobonding.

Since the part does not have to be post-processed, the tooling does not need to account for thermal expansion differences between the composite part and the tooling material. This in turn allows for the use of less expensive tooling material such as aluminum. Due to the speed of the process, only a small fraction of the heat required to process thermoplastics is transferred to the tool. After the first ply is placed the composite material acts as an insulator to further prevent thermal expansion of the tool. In fact, this process allows placement of thermoplastic material directly on to a 3-D printed mandrel or a magnet without damaging them when the proper precautions are taken placing the first ply.

For more information and detailed descriptions of these processes, visit our Resources page for technical papers and presentations, or contact us today using the button below!

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For more info on In-situ Consolidation and Cobonding, contact: 

Gabriel Benarroch
Business Development Manager

518-377-6471 x212| Email Gabriel