Ultra-stiff and strong composites for structures with complex geometries

Important results from the project

The material developed finds its inspiration in nature. Nature’s structural materials feature high stiffness, strength and damage tolerance. These materials uses staggered stiff inclusions embedded in a soft matrix, where the stiff inclusion carries the load and provides stiffness. Whereas the thin soft matrix transfers loads via shear and provides slip-planes in the material. Furthermore, the inclusions are considered two-dimensional materials as they have large length to thickness aspect ratios.

Expected long term effects

Here, we mimic the discontinuous architecture of natural composites to realise significantly stiffer and stronger man-made composites than ever before. Here, ultra-high modulus CFRP thin tapes constitute the stiff two-dimensional inclusions. Given the tape thickness of approximately 20 micrometre, very high volume fractions of the stiff tapes can be achieved. Use of short, thin, tapes is found to allow processing of structures from ultra-high modulus carbon fibres. Process needs to be improved to allow us to manufactur compsoites with fibre volume fractions of 60% or higher.

Approach and implementation

The project team collaborated in the material development and analyses to demonstrate 200 micrometre thick isotropic composite plates with stiffness in the range of 90-160 GPa, strength of 640-935 MPa and strain to failure (c.f. first-ply-failure) in the range 0.4-1.5% depending on the choice of fibre.