Strong and Tough Tape-Based Quasi-Composites inspired by Spider Silk

Fibrils are a dominant archetype in biogenic and synthetic structural materials. Composites relying on unidirectional fibers are limited in penetration resistance and are anisotropic. Advanced structures like Bouligands address these problems. One remaining deficiency of fibrous systems is the weak mechanical coupling between fibers. One possible solution is to flatten fibers to ribbons, to increase contact area between filaments. We found such natural materials systems, like certain cocoons, or the recluse spider’s ribbon silk. Our analysis has revealed that these materials have several other advantages, such as enhanced toughness, even at the single-filament level, or adhesive locking mechanisms. This can lead to van der Waals-based adhesive bonds surpassing the tensile strength of the tapes. Inspired by these findings, we have combined tapes with Bouligand-type approaches to make matrix-free “quasi-composites” with tunable mechanical properties and outstanding mechanical performance. We employ solvent cast printing to make such tapes and entire composites either by directly welding them together during manufacture or by stacking layer-by-layer afterward, resulting in quasi-composites with varying inter-tape adhesive strengths. Our stacked quasi-composites outperform the constituent tapes by up to 30% in strength and 290% in toughness. Our work presents the foundation to develop quasi-composites with high-performance tapes that significantly out-perform all existing fiber-reinforced composites.