Low Velocity Impact Damage Resistance Of Multi-layered/Hierarchical Thermoplastic Composite Sandwich Panels

Composite sandwich structures have been widely used in aeronautics,astronautics,transportation,wind energy and oceanographic engineering owing to the excellent mechanical properties,lightweight and multifunctional design characteristics.Loading conditions such as low-velocity impacts are inevitable in application.Studies on low-velocity impact resistance of thermosetting composite sandwich structures show that complex internal damages and failure mechanisms induced by low-velocity impact restrict the composite industrial application.Compared with thermosetting composites,thermoplastic composites have valuable and attractive advantages such as high toughness,low manufacturing cost,reparability and recyclability.But few research on low-velocity impact performance of thermoplastic composite sandwich structure are reported till now.Low-velocity impact resistance of multi-layered thermoplastic composite corrugated sandwich panels and multi-layered/hierarchical thermoplastic composite honeycomb sandwich panels are thus investigated.In particular,research have been studied in this paper as follow:Firstly,glass fiber reinforced polypropylene(GFRP)multi-layered corrugated sandwich panels were designed and fabricated by hot-pressing and hot-melting bonding methods.Quasi-static compressive tests were conducted and the corresponding numerical models were established via a VUMAT subroutine considering several typical failure modes to investigate the quasi-static compressive response and energy absorption mechanism by changing core configurations and core layer numbers.Deformation modes of two-layered corrugated sandwich panels with different core configurations were revealed.Results showed that the regular structure has the highest specific energy absorption,and the increase of core layers can improve the specific energy absorption of the structure.Secondly,Influence of variables including impact energy,impact location,core configurations and core layer numbers on low-velocity impact responses of multi-layered corrugated sandwich panels such as impact response and energy absorption mechanism were investigated.Symmetrical two-layered corrugated sandwich panels were found to have the highest energy absorption efficiency,and increase of layers reduce the impact damage on structure.A VUMAT subroutine considering several typical failure modes was established to study low-velocity impact response of corrugated sandwich panels and achieved good agreement with the experimental results.Then,Quasi-static compressive tests were carried out to evaluate the compressive response and energy absorption mechanism of the sandwich panel consists of woven glass fiber polypropylene face sheets and polypropylene honeycomb core.The results showed that increasing the layers of sandwich panel reduce the peak stress.A combination of experiments and numerical simulation was conducted to study the impact resistance of multi-layered honeycomb sandwich panels considering different impact energy,core heights and layers of sandwich panel.The results showed that the increase of core height reduce the impact peak value,prolong the whole impact process,and increase the layers of sandwich panel number can improve the damage resistance of the structure.Finally,Structural hierarchy was introduced to achieve the high properties with low relative density.A hierarchical thermoplastic composite honeycomb sandwich panel was fabricated by interlocking assembly technology applying the honeycomb sandwich panel as primary structure to form core ribbons and facesheet plates.The effects of impact energy on low-speed impact response and failure modes were studied.