Impact-Resistant and Tough Helicoidally Aligned Ribbon Reinforced Composites with Tunable Mechanical Properties via Integrated Additive Manufacturing Methodologies

Strong and tough structural materials occurring in nature have long fueled the search for an advanced class of strong biomimetic synthetic structural materials (SSMs). One such example in recent years is the rapid progress associated with the naturally occurring helicoidal composite structures inspiring the development of the tough helicoidally architectured synthetic structural composites (HA-SSCs). Most of the tough HA-SSCs have been fabricated using conventional composite resins and fibers or modern three-dimensional (3D) printing materials. Only recently, we ventured further into expanding the possibilities of imitating the helicoidal architecture in smaller scales (microns and tens of microns) while exploring the possibilities of utilization of various polymer-based composite formulas. In our previous research articles, we had established near-field electrospinning as an additive manufacturing methodology to construct tough and resilient 3D helicoidal membranes with micron-sized polymer fibers. In this article, we advance to the next level of developing fully composite structures from electrospun helicoidally assembled microribbons. A key aspect explored in this article is the importance of surface treatment. The physical, thermal, and mechanical experiments indicated superior adhesion between the components of composites, which led to enhanced toughness and impact properties. We further affirmed that reducing the helicoidal angular orientation of ribbons in the HA-SSCs can help further enhance the specific toughness and impact resistance of these composites. Furthermore, we found that the mechanical and physical properties of these composites can be tuned via several architectural features (helicoidal rotational angles, interface characteristics between layers and between ribbons) to suit the different strain-rate needs for various applications (combat army vest, sports gears such as helmets, flexible piezoelectric sensors, or polycarbonate-based solar photovoltaics (PV) modules). The experimental findings here suggest the importance of interfacial characteristics (between layers and between ribbons), the ribbon-to-matrix ratio, and angular arrangement of the ribbons as design guidelines for achieving next-generation HA-SSC materials, which are not only strong but also extremely tough and impact-resistant.