Environmental concerns lead manufacturers to use more and more composite material and also to think about their end of life and how to recycle them in order to limit their product’s carbon footprint. In this context, thermoplastic matrices and their recycling abilities are an opportunity and the use of thermoplastic tapes enable a longer storage than thermoset prepreg. However, composite materials are sometimes used in structural ways within severe environments. Current thermoplastic matrices are sensitive to temperature: the very significant variations of all the material’s properties near the glass transition Tg strongly impact its mechanical properties.

Our research team has been working over the past years on the behaviour of composites structures, especially under thermomechanical fatigue loading. A specific model, defined at the ply scale, has been developed and identified for Glass/Epoxy [1] and Glass/PMMA [2,3] composites. In this paper, experimental results for a carbon/thermoplastic composite material, made from tapes with the AFP process, and modelling results are presented. As this material is very new on the market, there is not much data about its mechanical behaviour especially under fatigue loading and the effect of the environment on its properties.

We aim at developing a model capable of considering several phases of mechanical loading combining quasi-static, long-term constant or fatigue loading coupled with different variations of the temperature.

Study

This work is based on the Ladeveze [4] meso-damage model, previously extended to fatigue loading [1,2,5]. The experimental results were used to identify the effect of long-term constant loading (creep) at various temperature and then adapt the damage evolution law of the fatigue model to take into account these additional effects.

During the experimental tests used to develop the model, a large experimental database was created including creep, fatigue and quasi-static tensile tests carried out at several temperature in a classical industrial range: -40°C, -10 °C, 20°C, around Tg ≈ 50°C and 80°C. For instance, before the tests, the samples were stored at various humidity ratio: 0%, 50% and 100% until their mass stop varying.

References

[1] D.Caous ; C.Bois ; J.-C.Wahl ; T.Palin-Luc ; J.Valette ; Procedia Engineering 2018, 213. 173-182

[2] E.Boissin ; C.Bois ; J.-C.Wahl ; T.Palin-Luc ; Journal of Composite Materials  2020, 54, 4269-4282

[3] E.Boissin ; C.Bois ; J.-C.Wahl ; T.Palin-Luc ; D.Caous ; International Journal of Fatigue 2021, 152, 106413

[4] P.Ladeveze ; E.Le Dantec ; Composites Science and Technology 1992, 43, 257-267

[5] J.Payan ; C.Hochard ; International Journal of Fatigue 2002, 24, 299-306