Abstract

Compression After Impact (CAI) test is normally used for the assessment of damage tolerance of composite laminates. The applicable specification for the execution of these tests is AITM 1-0010. However, for thicknessess under 4mm were buckling occurs, the applicable specification is the AITM 1-0077, which introduces the use of anti-buckling tooling covering the entire surface of the specimens. The tooling, which is used in the aeronautical industry  for the testing of thin specimens presents two problems which are the difficulty of assembly and of obtaining realiable results, and the visibility of the specimen during the test.

This work comprises the design, manufacturing and validation of a novel anti-buckling device for compression after impact thin specimens. For that purpose, a study of the specification toolings along with a review of the already developed anti-buckling tooling literature has been carried. As part of the validation process three series of impacted specimens of 3mm thickness.

This activity is developed as part of the project CERES, which is framed under Clean Sky 2, and has the main objective of validating the manufactured anti-buckling tooling. This tooling has been developed as an innovative solution for its application in compression after impact thin specimens. 

Abstract

RESUMEN: El uso de hidrógeno como fuente de energía es una estrategia prometedora para reemplazar los combustibles fósiles, además de las baterías y los biocombustibles. La industria aeroespacial europea ya está trabajando en el desarrollo de tecnologías de propulsión con emisiones reducidas o nulas y considera en gran medida la tecnología del hidrógeno. En la aeronáutica es favorable almacenar el H2 en forma líquida, LH2, a temperaturas de 20K para tener la mayor densidad de energía del combustible posible. Esto significa, que todos los materiales en contacto con el LH2 necesiten estar caracterizados a esta temperatura.

El INTA empezó a realizar ensayos criogénicos de materiales compuestos hace 27 años. Inicialmente en el ámbito de la caracterización de materiales compuestos de tanques para lanzadores reutilizables. Más adelante se ha investigado también la monitorización estructural de tanques de LH2, la detección de fugas de hidrogeno y pilas de combustible. Actualmente, el INTA está involucrado en la caracterización de materiales compuestos en proyectos de tanques de LH2 y las estructuras de material compuesto que llevan estos tanques para la aviación sostenible.

El articulo da una visión de las actividades realizadas en el campo de los ensayos criogénicos de materiales compuestos y facilita datos obtenidos en estos ensayos, comparando el comportamiento de diferentes materiales y diferentes tipos de ensayos. Además, se van a explicar las nuevas líneas de investigación que se están realizando en el INTA en la caracterización de materiales compuestos y su comportamiento antes y después de estar en contacto con el hidrogeno.

ABSTRACT: The use of hydrogen as an energy source is a promising strategy to replace fossil fuels, in addition to batteries and biofuels. The European aerospace industry is already working on the development of propulsion technologies with low or zero emissions and heavily considers hydrogen technology. It is favoured in aeronautics to store H2 in liquid form, LH2, at temperatures of 20K to have the highest possible energy density of the fuel. This means that all materials in contact with LH2 need to be characterized at this temperature.

INTA began to carry out cryogenic tests on composite materials 27 years ago. Initially in the field of characterization of composite materials for tanks for reusable launchers. Later, the structural monitoring of LH2 tanks, the detection of hydrogen leaks and fuel cells have also been investigated. Currently, INTA is involved in the characterization of composite materials in LH2 tank projects and the composite material structures that these tanks carry for sustainable aviation.

The article gives an overview of the activities carried out in the field of cryogenic tests of composite materials and provides data obtained in these tests, comparing the behaviour of different materials and different types of tests. In addition, the new lines of research that are being carried out at INTA in the characterization of composite materials and their behaviour before and after being in contact with hydrogen will be explained.