Periodic Reporting for period 3 - TAILTEST (Development of a multipurpose test rig and validation of an innovative rotorcraft vertical tail)
Reporting period: 2022-05-01 to 2023-12-31
In the line with the Clean Sky 2 objectives, the main objective of this project was to contribute to the reduction of fuel consumption and CO2 emissions by lowering the structural weight of a rotorcraft tail through application of thermoplastics. During the project the main goal were to design and manufacture a test rig and a load application system, which simulates critical flight condition. A goal associated to the flying Technology Demonstrator under WP B-4.2:”Pressurized Fuselage for Fast Rotorcraft”, is to support activities towards a “Permit to Fly” for test flights.
The main objectives of the project are:
• To perform structural tests and develop validated FE models to support the certification process of an innovative rotorcraft vertical tail.
• To develop, apply, and validate advanced numerical models for the simulation of debonding propagation in adhesively bonded or welded structural joints.
To achieve the main objectives, several intermediate steps have been solved:
• To design and manufacture an innovative multipurpose test rig to be used for testing a full-scale rotorcraft fin and parts of the fin structure like the spar-to-skin joints. The developed test rig includes a load application mechanism to apply loads representative of rotorcraft tail structures. Moreover, the test rig is designed so that a variable stiffness of the fuselage to the fin joint is achieved.
• To perform structural tests on a rotorcraft vertical tail, up to ultimate load for at least the representative load cases, applying an adequate number of conventional measuring sensors like strain gages (SGs) and Linear Variable Differential Transformers (LVDTs) or more sophisticated contactless measurement systems (e.g. Digital Image Correlation - DIC).
• To perform structural analysis of the fin utilizing the Finite Element Method (FEM) and validate developed numerical models by correlating displacement and strain measurements acquired during the structural tests with the respective numerical results.
• To develop advanced numerical models for the simulation of debonding propagation in composite structural joints.
• To perform mechanical tests to obtain the material properties required for the application of the above mentioned advanced numerical models for the debonding prediction.
• To design and perform a sub-scale structural test (e.g. on a spar-to-skin joint), using the multipurpose test rig.
The main objectives of the project are:
• To perform structural tests and develop validated FE models to support the certification process of an innovative rotorcraft vertical tail.
• To develop, apply, and validate advanced numerical models for the simulation of debonding propagation in adhesively bonded or welded structural joints.
To achieve the main objectives, several intermediate steps have been solved:
• To design and manufacture an innovative multipurpose test rig to be used for testing a full-scale rotorcraft fin and parts of the fin structure like the spar-to-skin joints. The developed test rig includes a load application mechanism to apply loads representative of rotorcraft tail structures. Moreover, the test rig is designed so that a variable stiffness of the fuselage to the fin joint is achieved.
• To perform structural tests on a rotorcraft vertical tail, up to ultimate load for at least the representative load cases, applying an adequate number of conventional measuring sensors like strain gages (SGs) and Linear Variable Differential Transformers (LVDTs) or more sophisticated contactless measurement systems (e.g. Digital Image Correlation - DIC).
• To perform structural analysis of the fin utilizing the Finite Element Method (FEM) and validate developed numerical models by correlating displacement and strain measurements acquired during the structural tests with the respective numerical results.
• To develop advanced numerical models for the simulation of debonding propagation in composite structural joints.
• To perform mechanical tests to obtain the material properties required for the application of the above mentioned advanced numerical models for the debonding prediction.
• To design and perform a sub-scale structural test (e.g. on a spar-to-skin joint), using the multipurpose test rig.
During the first project period, the innovative multipurpose test rig for testing a full-scale new design VTOL aircraft fin, as well as parts of the fin structure like the spar-to-skin joints was designed and manufactured. At the same time, a loading system was developed for loading V-shaped tail surfaces for non-standard flight cases of the VTOL-type aircraft. The developed test rig included a load application mechanism able to apply loads representative of VTOL aircraft tail structures. Moreover, the test rig was designed in a way that a variable stiffness of the fuselage to the fin joint can be achieved. After the first period the structural tests on a new design VTOL aircraft, up to the limit and ultimate loads for several representative load cases were conducted. A huge number of conventional measuring sensors strain gages (SGs), Linear Variable Differential Transformers (LVDTs)), and optical contactless strain measurement systems were installed and applied for data collection. Simultaneously numerical models were developed to perform structural analysis of the fin utilizing the Finite Element Method (FEM). Based on the test data developed numerical models were validated by correlating displacement and strain measurements acquired during the structural tests with the respective numerical results. Additionally, advanced numerical models for the simulation of debonding propagation in composite structural joints were developed. The models were supported by mechanical tests to obtain the material properties required by advanced numerical models for the debonding prediction. Finally, a sub-scale structural test (e.g. on a spar-to-skin joint) was designed and performed. These tests were used for the validation of the debonding numerical models at the sub-component level.
Project results are documented in several deliverables, the project leaflet, and the newsletter. 12 papers were presented at various international conferences (6th International Conference of Engineering Against Failure (ICEAF VI), European Conference on Fracture (ECF 23), EASN International Conference on Innovation in Aviation and Space for Opening New Horizons, International Conference on Strength of Materials, and 7th International Conference of Engineering Against Failure (ICEAF VII)). 4 open access papers were published in scientific journals. The project results were exploited through the two functional samples which document unique solutions of the Attachment of the Fin/aft fuselage segment, and RH dummy system that allows the replacement of one tail surface (FIN) and the introduction of a load into the fuselage so that multiple load cases can be represented without significantly changing the test configurations. This solution achieves significant time and cost savings compared to the situation where a full-scale test with both tail surfaces would be applied. The results of the TAILTEST project will be applied during the development and certification of the new Leonardo Next Generation Civil Tiltrotor (NextGentCTR) aircraft which is the main exploitation activity.
Project results are documented in several deliverables, the project leaflet, and the newsletter. 12 papers were presented at various international conferences (6th International Conference of Engineering Against Failure (ICEAF VI), European Conference on Fracture (ECF 23), EASN International Conference on Innovation in Aviation and Space for Opening New Horizons, International Conference on Strength of Materials, and 7th International Conference of Engineering Against Failure (ICEAF VII)). 4 open access papers were published in scientific journals. The project results were exploited through the two functional samples which document unique solutions of the Attachment of the Fin/aft fuselage segment, and RH dummy system that allows the replacement of one tail surface (FIN) and the introduction of a load into the fuselage so that multiple load cases can be represented without significantly changing the test configurations. This solution achieves significant time and cost savings compared to the situation where a full-scale test with both tail surfaces would be applied. The results of the TAILTEST project will be applied during the development and certification of the new Leonardo Next Generation Civil Tiltrotor (NextGentCTR) aircraft which is the main exploitation activity.
The TAILTEST project aims at contributing to the greening of the aviation industry in two ways: (a) by enabling the lowering of the structural weight of a VTOL aircraft tail through the experimental testing and the numerical simulation of a rotorcraft vertical tail fin and (b) by enhancing the use of novel hybrid bonded/bolter joints and thermoplastic composite materials that offer reduced required energy for manufacturing and improved recycling opportunities compared to the typically employed thermosetting composite material.
Within the project, major innovations with a strong impact on future manufacturing of VTOL aircraft structures and testing standards used for static and dynamic characterisation of adhesively bonded thermoplastic materials and structures are foreseen, namely:
1.Thorough structural characterisation and certification of the fin V-tail aircraft structure.
2.Development optimization and application of novel variable stiffness test rig to accurately represent the supporting structure behaviour during certification and validation tests.
3.Development of a multipurpose test rig to be used both for certification tests of a vertical tail fin, as well as, for validation tests of representative hybrid bonded/bolted joints.
4.Development and validation of theoretical and numerical models enabling better understanding of bonded joints debonding process and providing tools for the prediction of debonding evolution, both in static and dynamic loading conditions.
Within the project, major innovations with a strong impact on future manufacturing of VTOL aircraft structures and testing standards used for static and dynamic characterisation of adhesively bonded thermoplastic materials and structures are foreseen, namely:
1.Thorough structural characterisation and certification of the fin V-tail aircraft structure.
2.Development optimization and application of novel variable stiffness test rig to accurately represent the supporting structure behaviour during certification and validation tests.
3.Development of a multipurpose test rig to be used both for certification tests of a vertical tail fin, as well as, for validation tests of representative hybrid bonded/bolted joints.
4.Development and validation of theoretical and numerical models enabling better understanding of bonded joints debonding process and providing tools for the prediction of debonding evolution, both in static and dynamic loading conditions.