BS in Materials Engineering
Materials Engineering Department
Aptera (Oceanside, CA) has developed two epoxy-based, silica fiber-reinforced composites to be used on their three-wheeled all-electric vehicle called the 2e. Aptera’s composites were studied at temperature extremes using a dynamic mechanical analysis (DMA) system and by tensile and short beam shear (SBS) testing using an Instron testing system. These tests were conducted to simulate the loading of the composite in the 2e vehicle. Tensile and short beam shear samples were machined to 150 mm x 25 mm x 2 mm and 40 mm x 13 mm x 6 mm, respectively. DMA samples were machined to 30 mm x 5 mm x 2 mm. The average short beam shear strength at 180°F for resin systems A and B were 11.7 and 17.5 ksi, respectively. The average SBS strength at 0°F, were 49.2 and 37.4 ksi. The DMA tests utilized a dual cantilever bending process with a frequency of 1 Hz and a displacement of 0.02mm. The DMA results gave glass transition temperatures of 161°F and 168°F for Resin Systems A and B. The SBS and tensile samples of both resin systems failed prematurely at 180°F. In each case, the composite’s strength decreased with increasing temperature. Because 180°F is close to the Tg of either resin system, the fiber-matrix adhesion is weakened. As the epoxy passes through the Tg, a reaction takes place where the material becomes less stiff. Resin System B’s improved mechanical properties are a result of the epoxy’s higher glass transition temperature.