The stretch-induced wrinkling of thin films is solved through the modified von Kármán large deflection equations by first selecting the suitable deformation expressions that satisfy boundary conditions. Then, adopting the principle of minimum potential energy we obtain the deformations of simply supported rectangular thin films. The obtained significant deflections are nonlinearly elastic and of the lowest order of infinite solutions. The parameters of aspect ratio, the thickness and material of thin films are studied analytically and numerically. The highlighted results of wrinkle amplitude and load are in good agreement with experiments. The methodology also indicates the limit load impending plasticity and predicts the applied load precisely for each wrinkle. Further, it can be extended to the variety of multifunctional orthotropic and multi-layered thin films.

The mechanical properties of Ti/APC-2/Kevlar/epoxy hybrid composite laminates after low velocity impact were investigated at room temperature. There were three types of samples, including three layered [Ti/(0/90) s /Ti], five layered [Ti/(0/90) 2 / Ti ] s and nine layered [Ti/Kevlar/Ti/(0/90) 2 / Ti ] s. The lay-ups of APC-2 were cross-ply, while Ti layers were treated by chromic acid anodic method. Ti and APC-2 were stacked to fabricate the composite laminates via hot press curing process. Kevlar layers were added to fabricate nine-layered composite laminates via vacuum assisted resin transfer molding. The drop-weight tests were conducted with a hemispherical nosed projectile in 10 mm diameter. The impact loads were 5 kg and 10 kg and impact heights were adjusted to penetrate samples or the maximum height 1.50 m. The static tensile tests were conducted to measure the residual mechanical properties after impact. The free body drop tests were also simulated by using finite element method and software ANSYS LS-DYNA3D. The results showed that the bottom Ti layer absorbed more internal energy than the top Ti layer, then the cracks were found in the bottom Ti layer more often. The ultimate tensile strength reduced significantly after impact. The initial longitudinal compliance increased with the impact height increasing and decreased after the samples penetrated. Comparing the experimental data with the numerical results, it was found that the damage of the latter was more serious than that of the former. On the conservative side, the results of numerical simulation are acceptable and adopted for applications when no testing data available.

The mechanical properties and fatigue responses of double-edge-cracked Ti/APC-2 hybrid nano-composite laminates by tensile and cyclic tests were obtained. The double-edged cracks were cut with the crack lengths of 2.0 mm and 3.0 mm symmetrically and anti-symmetrically. The mechanical properties of symmetrically cracked samples are more detrimentally than those of anti-symmetrically counter parts. The greater the cracked angles, the greater the maximum load, however, the results of crack

The mechanical properties, wrinkling phenomenon and fatigue response of polymeric polyethylene rectangular thin films due to both static tensile and cyclic tests were investigated. From the tensile tests we obtained the stress-strain curves and observed the formation of wrinkles for original films. The evolution of wrinkles resulted from in-plane to out-of-plane deformation and deflection. Also, the tensile tests for notched films were performed such as with a central hole, two vertical holes and two horizontal holes. From the fatigue tests the total strain vs. life curve was achieved. It was composed of two straight lines of both elastic and plastic parts.