The project completed the following major tasks. The Blade concept was designed as a full and scaled model. The scaled model design was simulated and shown to cause the same damage as the full model on the fuselage and as seen by the damage mechanisms in the blade and the rate of energy absorption. Material coupons and impact plates were modeled, manufactured/fabricated, and tested which led the way for calibration of the composite multi scale progressive failure models to be developed. Low level plate impact testing was performed which determined the ballistic limit for this specific composite. Impact simulations validated the testing results and showed failure mechanisms inside the composite. Blade sections were then designed for specific mass and stiffness requirements with three choices for layups determined. One was down selected. The simulations began on the full and scaled blade models which had the blade impacting the fuselage at two different angles. It was shown that the fuselage could survive the blade impact and that the scaled model with a tuned layup different from the full blade can be utilized in test to save cost of manufacturing and test plan.
The project began with an initial blade designs from analytical and FE models meeting Airbus requirements of mass and stiffness distribution along the length of the blade.
For the Initial Blade Design, three admissible material and lamination scenarios were determined, in compliance with requirements set by Airbus. These scenarios include the following conceptual cases: (1) single material & uniform section layup, (2) multiple materials & uniform section layup, and (3) multiple materials & stiffened sections. The third scenario with both fabric (0/90) and (+-45) for skin and unidirectional materials for girders was chosen as the best candidate. The blade design was enhanced with additional reinforcement layers on the FE model and Rohacell HT71 foam inside the blade and was shown to meet all stiffness requirements for flapping, lead-lag, tension, and torsion.
The material class was chosen and finalized as IM7-RTM-6. Manufacturing of coupons and low level plate impact specimens began. The following coupons were tested for unidirectional coupons: in plane tension, compression, and shear tests. For the weave tension, compression, three point bending, DCB fracture, and ENF fracture. Multi scale multi physics composite durability and damage tolerant models were built using unidirectional tests as calibration and weave tests as validations. This completely formed the progressive failure damage mechanics models for impact predictions.
Detailed plate impact testing was performed on 300x300x5mm3 Woven-Carbon/RTM6 Epoxy plates with a 30mm spherical steel impactor. Various velocities were to be considered in order to experimentally determine the ballistic limit. Three different energy levels were decided, namely under/at/over the ballistic limit of the material. The velocities corresponding to these cases were 56, 80 and 96m/s. Each case was repeated twice to ensure repeatability of testing with high speed cameras showing impact event and NDE C-Scans revealing damage area around footprint. Simulations were performed with success with correlation between test and simulations. Ballistic limits were simulated, along with other velocities under the limit, showing fiber, matrix, and delamination damage similar in size and shape to C scans.
Blade impact models on curved fuselage structures with both full and scaled models were performed. Using an innovative damage equivalency technique that designed scaled models, impact simulations of the full and scaled FE models showed similar damage patterns on the fuselage and energy absorption rate. The scaled blades, 70% of full model, could be manufactured to save manufacturing cost and produce same test results as the full blade. The impact simulations showed the fuselage to survive Airbus impact requirements. The models showed the amount of plastic deformation was small and no penetration happened.
With all the building block simulations, manufacturing, and test verifications performed this was a successful project.
The only item left uncompleted for unfortunate reasons was to manufacture scaled blades and ten (10) partial blade components sections from root, mid, and tip.
