A comprehensive computational micromechanics has been presented to predict the transverse mechanical properties and failure envelop of bi-axial stress in a 22-33 plane at high temperatures. First, a paraboloidal elasto-plastic damage model considering the temperature effect of epoxy has been employed. Then, in order to rapidly create the random fiber distribution of the representative volume element (RVE), a simple and effective algorithm of fiber placement and an auto modeling and calculating python script have been developed, where the thickness size effect of RVEs has been discussed. Finally, the transverse tension/compression and out-of-plane shear properties and the corresponding failure envelop of RVEs are analyzed systematically by means of finite element simulations. The results show that the in-plane shear strength exists strongly thickness size effect, and high temperature can significantly weaken the transverse strength, especially for transverse compression, and the temperature effect of modulus can be depicted by a specific Gaussian function. In addition, Hashin and Tsai-wu criteria may be more appropriate to predict the bi-axial failure envelop of ${\sigma }_{2}2-{\tau }_{23}$ at high temperature, and Tsai-Wu criterion is better and more suitable than Hashin and Catalanotti criteria for considering bi-axial compression.

Bio-jet fuels prepared by the thermochemical conversion of triglyceride can be used as complete substitutes of jet fuels. A bio-jet fuel prepared as a substitute of the RP-3 jet fuel and the RP-3 jet fuel itself were, respectively, used to fuel a small aviation piston engine. The characteristic tests of the engine were carried out, and the performances of the power, economy, emissions, and heat release law of the engine fueled with the two fuels were analyzed. The feasibility of the bio-jet fuel as a substitute for the RP-3 jet fuel was proved by the experimental results, which show that when the engine is fueled with the bio-jet fuel, the power and economy performance do not deteriorate; however, the HC emissions increase at small and medium throttle openings, while at large throttle openings, the performances of power and economy decreases, the emissions of HC and NO_x increase, and the CO emission decreases. The bio-jet fuel is more prone to spontaneous combustion than the RP-3 jet fuel, so knock combustion would be more likely to occur at large throttle openings, and large cooling air flux is required to cool the cylinder because spontaneous combustion would increase heat release.

In accordance with the metal-composite structure ice impact status, an experiment of Ice Impact on Aluminum/Carbon Fiber Reinforced Composite dual plate was carried out to study the dynamic responses and damage of the target dual plate. The artificial ice ball with a diameter of 35 mm was launched by a 37 mm gas gun test system to impact the metal face of the plate, high-speed photography was used to measure the launching speed of ice balls and record the impact process. The internal damage of composite plate and the displacement of metal part were measured. Experiment results showed the external damage of the composite plate was mainly manifested by the shallow elliptical impact dent formed on the impact surface contacted with the aluminum plate, with the increase of the impact energy level, the damage on the back of the plate became more serious. When the impact energy reached 400 J, the back of the plate was damaged by fiber breakage. The internal damage measurement results showed The internal delamination shape of the [0/90]_4s plate and the [0/45/90/-45]_2s plate were similar to that of the cross-shaped and plum blossom-shaped laminates, respectively, and the delamination failure was mainly caused by interlaminar shear stress due to the different bending stiffness between layers.

Cyclic response and fatigue behavior are sensitive to the microstructure of material induced by heat treatment. In this paper, three sets of high-temperature superalloy Inconel 718 with different heat treatment, namely annealed, aged, and directly aged high quality (DAHQ), are compared. Difference in grain size distribution, phase, and precipitate, etc., were investigated using an optical camera and scanning electron microscopy. Yield and ultimate strength were found to increase obviously after aging heat treatment. Self-heating phenomenon at 20 kHz was attenuated as grain size decreased. There was a transition from cyclic hardening to softening. Very-high cycle fatigue (VHCF) behavior of Inconel 718 was tested using an ultrasonic fatigue device. Crack initiation duration occupied greater than 99% of the total fatigue life. It concluded that average grain size influences VHCF strength and crack initiation mechanism, and that self-heating phenomenon is not a decisive factor on VHCF strength for Inconel 718.