Investigating the effect of layer arrangement and optimization of airplane windshield layering against bird strike

نوع: Type: Thesis

مقطع: Segment: PHD

عنوان: Title: Investigating the effect of layer arrangement and optimization of airplane windshield layering against bird strike

ارائه دهنده: Provider: فرشید خلوصی - مهندسی مکانیک

اساتید راهنما: Supervisors: Dr. Ali Alavi Nia

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr.Hashem Mazaheri-Dr.Hamed Ahmadi-Dr.Saeid Feli

زمان و تاریخ ارائه: Time and date of presentation: 2025

مکان ارائه: Place of presentation: آمفی تئاتر مهندسی

چکیده: Abstract: Bird strike is a major threat to aerial structures, including aircraft. In this thesis, numerical and experimental methods were used to investigate the ballistic resistance of windshields made of main layers (glass and polycarbonate) and interlayers (PVB, SG and TPU) with different layouts against bird strike. Experimental tests were used to investigate the mechanical properties of each layer. Compression and Brazilian tests at different strain rates, as well as a bending test, were performed on the glass material. Quasi-static tensile and compression tests, as well as a dynamic mechanical analysis test, were used to compare the mechanical properties of the interlayers. The results of these tests showed that the behavior of glass was strongly dependent on the strain rate and the energy absorption of the TPU interlayer was higher than that of the other studied interlayers. In the compression test with a strain rate of 0.83 s-1, the ultimate compressive strength of TPU was about 103 MPa. While this value was 57.9 and 148.8 percent lower for PVB and SG samples, respectively. Also, according to the results of the dynamic mechanical test, TPU and SG have the lowest and highest glass transition temperatures, respectively. Subsequently, the bird strike test on the windshield was conducted in accordance with the CS-25 standard. According to this standard, a bird with a mass of 1.8 kg is thrown towards the windshield. The bird strike test was conducted in the speed range of 110-180 m/s. In order to calculate the impact speed, 4 laser velocity meters were used. The angle of impact of the bird to the windshield was considered to be 45 degrees, in accordance with the angle of installation of the windshield on the aircraft. In general, 6 bird strike tests were conducted on windshield with different layouts. The windshield deflection due to the bird strike was measured using the Hall effect. For this purpose, 9 positions on the windshield were identified to calculate the amount of windshield deflection at different locations. In order to reduce the time and cost of the bird strike test, a numerical method was used. The simulation of the bird strike on a windshield was performed in the finite element software LS-Dyna. After ensuring the acceptable accuracy of the simulation results, a parametric study was conducted. The parametric study included the effect of the type of layouts, adding a polycarbonate layer instead of glass, different windshield interlayers, bird strike speed, the angle of the bird strike with respect to the windshield, and the bulk material model. The results of this study showed that the type of interlayer has a significant effect on the strength of the windshield. The windshield with pure SG interlayer ruptured due to its low toughness. The windshield with pure TPU interlayer showed greater resistance than SG. The TPU interlayer had a lower deflection value (about 10%) than the PVB interlayer. The results of bird impacts on W-S-11 and W-S-13 windshields and W-S-12 and W-S-19 windshields showed that by placing a thicker glass layer as the back layer and a thinner layer in the front, the windshield deflection decreased by about 16.9%. As the interlayer thickness increased, the windshield strength increased. The angle of impact had a significant effect on the deflection and the shape of the damage. As the angle of impact increased, the windshield deflection decreased. Also, changing the interlayer layout caused a change in the windshield behavior. The results also showed that when the thickness of the front interlayer increases, the amount of windshield deflection decreases. The use of a polycarbonate layer instead of a glass layer was also investigated. The results showed that the polycarbonate layer provides more strength to the windshield than glass. When polycarbonate was substituted instead of glass in the front layer, the highest amount of windshield strength was achieved. The ballistic limit speeds of the W-F-1 and W-F-2 windshields were about 174 and 114 m/s, respectively. Also, at impact speeds less than 100 m/s, the amount of deflection was almost the same for the two models. Afterwards, in order to more accurately investigate the effect of each layer type on the functions of the amount of energy absorbed, mass, and the ratio of energy absorbed to mass, and also to find a target with an optimal layout that has the highest ratio of absorbed energy to mass, optimization was performed. Optimization was performed in Minitab software using Taguchi method. Finally, in order to reduce the simulation time, a bulk material model was proposed. The proposed bulk model was able to predict the windshield behavior with good accuracy. By using the bulk model, the time required to execute the simulation was reduced by about 75% compared to the laminate model.