Sustainable lightweight construction: »Light Materials 4 Mobility«

In this project, new, sustainable lightweight solutions were developed in mate-
rial and process technology, with the aim of maximizing resource efficiency. In the ”Bio Tape“ subproject, the focus was on the development and demonstration of a fiber-reinforced biopolymer system for lightweight structures based on:

  • optimized and recyclable PLA formulations,
  • cellulose regenerate fiber-reinforced injection molding material and
  • basalt-fiber-reinforced UD tapes with a PLA matrix.

In addition, to demonstrate recyclability, the recycling of the materials using caustic or enzyme treatment was investigated The recycling method allows the recovery of the basalt fibers and the monomeric lactic acid. The PLA formulations developed show heat distortion temperatures of up to 140 °C, optimized crystallizability and higher degrees of crystallization, increased ductility, and improved hydrolytic stability.

Hybrid seat back made of basalt fiber
© Fraunhofer ICT
Hybrid seat back made of basalt fiber

By pretreating chemical pulp with caustic soda to optimize the molecular
weight distribution or the degree of polymerization, and by adjusting the solution spinning process, the stable production of regenerated cellulose fibers was possible. The orientation of the cellulose crystallites in the fiber direction resulted in an E-modulus up to 18 times higher than that of regenerated cellulose fibers available on the market. Injection molding material with a PLA matrix and 20 percent fiber reinforcement was produced in a double pultrusion process. In mechanical testing, the composite achieved a Young’s modulus approximately 15 percent higher than that of comparable commercial material systems. The modified matrix systems enabled the production of basalt-fiber-reinforced UD tapes with homogeneous fiber distribution and fiber mass fractions of up to 63 percent The mechanical composite properties were raised to a level comparable to that of the polypropylene/basalt fiber reference system.

Using the optimized fiber-reinforced biopolymer system – based on injection molding material and continuous-fiber-reinforced UD tapes – and the adaptation of the manufacturing processes, a seat structure demonstrator could be produced.

"Biobased materials make a valuable contribution to achieving national and European climate protection and sustainability targets in transport technology."