Study For Mechanical Properties Of Directional Plexiglas By Experiment And Numerical Simulation

The mechanical properties of directional Plexiglas attract more and more attentions from industry and science since several planes crashed due to the cracks in the hatch. In the paper two specimens along different directions were cut from a directional Plexiglas plate. Isodyne method is applied to measure the stress states of directional Plexiglas. Isodyne images of different specimens along different directions reveal the anisotropic mechanical behaviors in directional Plexiglas. So an anisotropic mechanics model is established to describe material mechanical properties of directional Plexiglas which is determined by five independent elasticity constants.Digit frequency domination correlation method is applied to measure elasticity constants. Recording the gray images of tested object before and after loading two ways could be selected to analyze the surface displacement of the tested object. One way is the analysis of point by point method and the other is full field analysis method. Point by point analysis method is chosen in the paper. Through analyzing elasticity constants along different directions the conclusion which reveals the anisotropic mechanical behaviors in directional Plexiglas is got: along the direction of directional tension, the mechanics properties are enhanced, while along the vertical direction of directional tension, the mechanical properties are weakened.Because of the anisotropic mechanical behaviors in directional Plexiglas, in the paper fracture toughness values are tested along two directions: one is along the direction of directional tension, the other is along the vertical direction of directional tension. The specimen is very small, so there is not enough space to put extensometer.In the paper digit frequency domination correlation method which substitutes extensometer is applied to test crack opening displacement V. Fracture toughness values along the direction of directional tension is larger than along the vertical direction of directional tension. The conclusion is that surface crack along the vertical direction of directional tension expands more easily than the crack around the hole used for connecting along the direction of directional tension. So it is necessary to pay more attention to surface crack in the hatch.Based on anisotropic mechanics model and elasticity constants, Finite element method is applied to test stress and strain distributions of crack tips along different directions which are displayed by matlab software for comparing with experimental result. Through analyzing stress and strain values the conclusion is that surface crack expands more easily than the crack around the hole used for connecting which is coincident with experimental result.Lastly thermo-optical curve which reflects temperature property of directional Plexiglas is tested. It will be foundation to study mechanical properties of directional Plexiglas under different temperatures.