3D printing of reinforcements made of fiber composite material

Concrete has excellent compressive strength, but only very limited tensile strength. For concrete structures such as foundations, beams, columns and ceilings, steel reinforcing bars are therefore usually installed to absorb the tensile forces that occur. The production of such reinforced concrete components is energy-intensive and harmful to the climate. In addition, the service life of reinforced concrete structures is limited due to their susceptibility to corrosion.

State of the art

One alternative is to use bars and mesh made of carbon fiber composite material. Such composite reinforcements do not corrode and the specific tensile strength is higher than that of steel. This makes it possible to build lighter and with less material. As a result, the component cross-section is reduced and concrete is saved. The reinforcement parts can be shaped more individually according to the loads to be carried than before. However, the fibers and their processing are currently cost-intensive. Researchers are therefore working on economical processing methods.

Technology

Researchers at KIT have developed an alternative 3D printing process based on electromagnetic heating that processes continuous fiber-reinforced thermoplastics (CFRTP) at high speed. In order for the plastic material to pass through the injector, it must be soft enough and malleable due to heat. This is achieved with a microwave applicator as the print head, which enables uniform and rapid heating even with large filament diameters. In contrast to conventional heating, microwaves generate the heat directly in the material. The poor thermal conductivity of plastic, which limits the printing speed in conventional filament 3D printers, is then irrelevant. Microwave printing technology enables the flexible production of mechanically resilient carbon fiber composite structures as reinforcement.

Advantages

With a printing speed up to ten times faster than conventional technologies, the additive process offers great potential for many industrial applications. As part of the Helmholtz validation project MWPrint4ReCon, a robot-based prototype of the microwave printer, including a path planning and control system, was set up at KIT.

Options for companies

KIT is looking for development partners from the software, printing and construction industries to use the process for printing three-dimensional reinforcement structures made of carbon fiber composite material.