Temperature effect on the single and repeated impact responses of intraply flax/basalt hybrid polypropylene composites

Low-velocity impacts can severely jeopardize the structural reliability of polymer composites. In view of this, the present work provides a thorough overview of the impact response of polypropylene (PP) composites reinforced with an ecofriendly intraply flax/basalt hybrid fabric, assessing the effect of different parameters: energy level, temperature, and number of impacts. Indeed, high-energy single impacts are as dangerous as low-energy repeated impacts for the structural integrity of laminates. Moreover, considering the poor interfacial adhesion between hydrophobic polyolefin matrices and hydrophilic vegetable fibers, the effect of a maleic anhydride coupling agent was evaluated. A detrimental effect of coupling agent on composites impact response was observed, determining a reduction of the impact life (impacts to failure from 83 to 63 at 10 J and from 30 to 9 at 15 J) because several energy dissipation mechanisms were prevented. Decreasing temperatures (-40°C) caused an embrittlement effect on neat PP composites with an increase between 7.3% and 20.3% of maximum force and a decrease between 7.5% and 10.9% of maximum displacement, whereas increasing temperatures (80°C) led to a softening of compatibilized composites with a decrease between 13.8% and 27.5% of maximum force and an increase between 28.1% and 34.4% of maximum displacement.