Investigation on strain rate sensitivity of 3D printed sPEEK-HAP/rGO composites

Abstract

Nanofillers can be added to polymers to improve their mechanical behaviour. However, the yield behaviour of most polymer composites is influenced by strain rate. The majority of the research focused on the behaviour of polymer composites at high strain rates. This work aims to investigate how hydroxyapatite (HAP) and reduced Graphene Oxide (rGO) nanofillers affect the mechanical properties of sulphonated polyetheretherketone (sPEEK) at low (tensile and compression behaviour) and high strain rates (compression behaviour). The thermal, mechanical, and toughness responses of sPEEK filled with HAP and varying Mf of rGO (0.5%, 1%, and 1.5%) at different strain are studied in detail. The strong strain rate effect was seen in HAP and rGO loaded sPEEK composites. The strain rate sensitivity factor of sPEEK-HAP/rGO increased with strain rate but reduced with increased rGO concentration. Under low strain rate compression, HAP and rGO loaded sPEEK absorbed approximately 4% more energy at Mf of 1.5% than the neat sPEEK. Higher concentration of rGo (1.5%) withstood better melt processing, and demonstrated excellent integrity inside the sPEEK-HAP matrix. Increased rGO density resulted in lower sPEEK-HAP composite density and better mechanical characteristics, even at low strain rates. MFI decreases as rGo concentration increases, which might resolve printing issues. The increased compatibility between sPEEK-HAP and rGO particles was demonstrated by SEM images.