Toughened Bio-Polyamide 11 for Impact-Resistant Intraply Basalt/Flax Hybrid Composites

The automotive sector covers almost 40% of polyamide (PA) total demand. A suitable solution to improve the sustainability of this sector is the exploitation of PA matrices sourced from renewable origins, such as PA11, and their reinforcement with natural fibers such as vegetable flax and mineral basalt. A preliminary study on the quasi-static properties of PA11-based composites reinforced with an intraply flax/basalt hybrid fabric demonstrated their feasibility for semi-structural purposes in the transportation field, but their application needs to be validated against dynamic loading. In this regard, this work investigated the low-velocity impact performance of PA11 flax/basalt hybrid composites (10 J, 20 J and 30 J) as a function of temperature (room temperature and +80 °C) and plasticizer addition (butyl-benzene-sulfonamide). The results proved that plasticized PA11 is endowed with a lower glass transition temperature (~15 °C, from DMA) and melting temperature (~10 °C, from DSC), which simplifies manufacturing and processing, but also possesses a higher toughness which delays penetration phenomena and reduces permanent indentation at room temperature between 20.5% and 42.8% depending on impact energy. The occurrence of matrix plasticization at +80 °C caused a more flexible and tougher response from the laminates with a decrease in linear stiffness and a delay in penetration phenomena which made the plasticizer effect less prominent.