Research On Stretch Machine Mechanical Properties And Stretching Process Of Aviation Plexiglass

The plexiglass is widely used in aviation.With the rapid development of aviation technology,higher requirements are put forward for the performance of aircraft transparent parts.In order to better match the current aircraft and adapt to the complex environmental conditions in the air,it is necessary to toughen plexiglass.Among many toughening methods,the effect of biaxially oriented stretch technology is the most superior,and it is currently the most important plexiglass modification technology in the aviation industry.At present,domestic and foreign scholars mainly study the properties of oriented plexiglass,but lack of research on biaxial stretching equipment and stretching process.This paper analyzes the mechanical properties and stretching process of aviation plexiglass stretching machine.Based on the detailed analysis of the structural characteristics and stretching principle of the aerospace plexiglass stretching machine,the main beam and clamping structure were reasonably simplified,and then the force analysis was carried out.The finite element simulation analysis of the main beam was carried out,and the stress and deformation cloud diagram of the structure was obtained,and the weakest position of the structure is clarified.The optimized structure was obtained by setting the main beam variables as width and tension center distance,and the rationality of the structural strength and stiffness was verified by the check formula.The finite element simulation of the clamping structure was carried out under the maximum load during clamping and after cooling.According to the results,the clamping range is defined and the structural strength is verified to meet the requirements.Based on the thermomechanical coupling theory of viscoelastic materials,the WLF time-temperature equivalence principle was used to simulate the viscoelastic properties of the plexiglass by of Prony series.The finite element simulation of the biaxial stretching process of plexiglass at different stretching speeds and temperatures was carried out,and the influence of different parameters on the stretching force was analyzed.The results showed that the optimal stretching speed and temperature for biaxial stretching of plexiglass were 30mm/min and139°C,and obtain the displacement-stretching force curve and displacement-stretching force expression of the clamping zone at this stretching speed and temperature.In order to reduce the shrinkage force generated by the plexiglass during cooling,a natural cooling setting simulation was carried out on the basis of obtaining the optimal parameters,and the retraction of the tie rod was used to effectively reduce the shrinkage force exceeding 10000 N.Finally,a biaxial tensile test of 35 mm thick plexiglass was carried out according to the obtained process parameters.,and the simulation and experimental results are compared,and the trend of the two is consistent,and the error is small.Through the finite element simulation of 50 mm and 75 mm thick plexiglass,the process parameters of biaxial stretching of 50 mm and 75 mm thick plexiglass are given.