INTRODUCTION 

The HexTOOL™ material is a new composite solution for manufacturing molds to produce aerospace components. HexTOOL™ uses Hexcel’s established HexMC® technology. This product consists of high strength carbon fiber, with a nominal fiber volume of 60%, and HexPly M61 BMI (bismaleimide) resin, at 40% resin content, cured at 190 °C in autoclave under 7 bar pressure. This is an alternative to conventional tooling materials, including metal. 

HexTOOL is characterized by an excellent temperature resistance (up to 220°C), and a structural complexity that is different from conventional composites. The HexTOOL ply is composed of unidirectional impregnated short carbon fibres (60 × 80 × 0.15 mm), which are randomly arranged in the ply plane. The whole assembly forms a thick composite, which is quasi-isotropic in the ply plane. Thanks to its particular structure and its machinability and repairability properties, this material is well suited for the manufacture of composite molds. 

REQUIRED WORK 

In this context, we study the durability of the HexTOOL composite under fretting sollicitation. Fretting is a mode of contact loading in which the contact is subjected to vibrations of low amplitude (force or displacement driven, generally) but causing local damage. Depending on the amplitude range, fatigue or wear damage mechanisms may occur. The influence of parameters such as applied load (stress), temperature, as well as the morphology of the microstructure on the mechanical behavior and damage are among the main areas of interest. The globally isotropic behavior of the material is challenged at the scale of the tested surfaces. An analysis of the local behavior and structure is essential for a detailed understanding of the tribological response of the material. 

Moreover, the experimental protocol requires a series of preliminary characterizations of the samples, in order to have the necessary elements for the post-treatments and analyses of the damaged surfaces by comparison before / after test. This work includes the following items : 

• Literature review   

• Selection of a list of preliminary data on the samples to be studied with the project supervisors 

• Preparation and drafting of a complete analysis protocol for data sets (before testing : which quantities to measure, which test means and measurement parameters, which processing and analysis software to use / after testing : how to post-process the damaged surfaces) 

• Characterization tests (hardness, scratch, surfometry, microscope / SEM ) 

• Realization of damage tests on fretting bench 

BIBLIOGRAPHY 

[1] O. KLINKOVA et al., 2011 https://doi.org/10.1016/j.triboint.2011.09.006 

[2] G. CHARDON et al., 2015 https://doi.org/10.1016/j.triboint.2014.09.002 

[3] S. TEREKHINA et al., 2011 https://doi.org/10.1016/j.triboint.2010.11.014