Enhancing the endurance of UAVs by the use of structural power composites: System-level study of a flying wing

Sammanfattning: This thesis studies the feasibility of integrating the novelStructural Battery (SB)[1] into the airframe of a UnmannedAerial Vehicle (UAV). The potential advantages in terms ofmass, range and endurance are studied.The aircraft performance is analysed using conventionalflight mechanics, modelled in Matlab and Xfoil. The structureis designed and analysed using composite laminate theoryand beam theory in conjunction with verification in AnsysMechanical. An iterative procedure was used to arriveat a design that satisfied the set structural- and flight requirements.The currently demonstrated structural battery has a specificenergy density of 23.8Wh/kg, an elastic modulus of25GPa and tensile strength of at least 300MPa.[1]The laminae properties used in this master thesis were estimatedusing the Reuss and Voigt model combined with theRule of Mixtures (RoM). A quasi isotropic SB laminate wasmodelled according to the previous structural requirementsand assumed material properties. It yielded an elastic modulusof 54GPa. In order to simplify the analysis the energyand stiffness were decoupled. The SB was assigned a specificenergy of 23.8Wh/kg and 60.6Wh/kg according to thevalues measured and estimated previously[1].A SB with a tensile modulus of 54GPa and specific energyof 24Wh/kg was shown not to be beneficial to integrate intothe primary aircraft structure. The designed SB yieldeda reduction in flight range of 5.8%. This was shown bycomparing the designed SB with a reference aircraft configuration.The reference configuration uses a conventionalbattery that has a specific energy density of 160Wh/kg andconventional Carbon Fibre Composite (CFC) with an elasticmodulus of 71GPa.It was shown that the integration of the SB modelled wouldbecome beneficial compared to the reference aircraft configurationwhen the SB specific energy exceeds 33Wh/kg.The integration of a structural battery with a specific energyof 60.6Wh/kg yielded a flight range improvement of16.9% compared to the reference aircraft.