Composite structural supercapacitors were fabricated using an adhesive polymer electrolyte, mixture of epoxy, PVDF, and lithium trifluoromethanesulfonate (LiTFS). Multi-cell supercapacitors were made into composite panels. Each cell has a planar configuration with metal foils and carbon fiber as mechanical reinforcements/currrent collectors, carbon powder/carbon naotubes as active materials, and the adhesive polymer electrolyte as the matrix. A systematic study on the adhesion, in-plane tensile strength, and conductivity versus composition of the adhesive polymer electrolyte was conducted. The conductivity of the epoxy based adhesive polymer electrolyte is in the magnitude of 10^-2 S cm^-1 when the concentration of epoxy resin is less than 30%. Structural SCs were fabricated using a vacuum bagging method. The maximum specific energy is achieved as 2.64 Wh kg^-1. The mechanical property of the structural SCs in this work is acceptable. The greatest ultimate tensile strength (UTS) of the structural SC can reach 80 MPa while the UTS of the baseline structural SC is 112 MPa. The strength of the structural SCs can be improved significantly using a stronger epoxy. The response of electrochemical performance of the structural SCs to in-plane tensile stress was studied. Before fracture, the specific power and the specific energy increases slightly or remains the same.