|High performance fiber reinforced polymer composites for lightning strike protection
|Zhou, Limin (ME)
|Hong Kong Polytechnic University -- Dissertations
Airplanes -- Materials
|Faculty of Engineering
|xvi, 138 pages : color illustrations
|Composite materials play a significant role in current and future aircraft structure due to their exceptional specific strength and stiffness. The usage of composite materials is attracting because reduced weight allows better fuel economy and lower operating cost. However, conductivities of fiber reinforced polymer (FRP) composites are relatively low compared with traditional metallic materials which hinders further application of composite materials. Lightning strike is one of the most hazardous threat to aircrafts' composite structures. It is unpredictable, capricious and can cause both direct and indirect damages to aircrafts . The current solution is mainly based on attaching a kind of metallic protection structure over the composites , however the adding weight of metallic lightning strike protection (LSP) system reduces the fuel savings of composite structures. The development of functional composites with highly conductive properties is desired to protect aircrafts against lightning strike. An alternative solution for LSP is developed in this study by introducing carbon nanotubes (CNTs) and multi graphene platelets (MGPs) into composite structure then results great improvement in both mechanical and functional properties [3, 4]. In this study, CNTs were successfully grown on carbon fiber at 550°C under N2/H2 atmosphere using chemical vapor deposition (CVD) method. Multi graphene platelets (MGPs) was then coated on surface of CNTs-grown carbon fiber. Specimens with uppermost ply modified by carbonaceous nanoparticles were fabricated using two different techniques, they were respectively vacuum assisted resin transfer molding (VARTM) and hand lay-up with autoclaved process. The grown CNTs were identified by scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM). Material properties were further determined through 3-point bending, short beam shear test and conductivities (electrical, thermal) test. A noticeable synergetic effect of CNTs and MGPs builds up phonon transport and electron transfer pathways in the structure then results high functional conductivities. At the same time, mechanical properties were also enhanced by CNTs and MGPs. The electrical conductivities were improved 181 %, 1427 % and 999 % respectively at in plane, through thickness and surface directions. The thermal conductivity of through thickness direction was improved by 48 %. For mechanical properties, interlaminar shear strength was increased by 3 % while the flexural modulus and flexural strength revealed 27 % and 14 % improvement respectively. The Izod impact resistance was also increased by 26 %. The control and modified composite was then simulated in ABAQUS to explore its protecting efficiency against lightning strike. The numerical results revealed that both damage volume and depth were decreased dramatically compared with control composite material. The total damaged layers decreased from 8 plies to 2 plies. This study offers new generation carbonaceous nanoparticles modified carbon fiber reinforced polymer composite which can be applied to minimize or prevent lightning strike's damages to aircraft's composite structures.
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