The mechanical behaviour of organic matrix composite materials such as T700GC/M21 carbon fibre reinforced polymer (CFRP) is generally considered by the industry as being orthotropic elastic for the sizing of aeronautical structures under normal isothermal "static" flight loads. During the aircraft lifetime, it may be exposed to severe loading conditions at various temperatures. However, the mechanical behaviour of CFRP is known to exhibit a linear behaviour or a non-linear behaviour according to the types of loads that are considered creep or extreme conditions. The observed non-linearity can be commonly attributed to several physical phenomena such as non-linear viscosity, plasticity, or damage.In the literature, different models can be found that are based on three components: a first elastic reversible behaviour, a second non-linear behaviour, and a failure criterion. An important issue is to understand and characterize the transition between the elastic reversible behaviour and the non-linear behaviour. To answer this question, the present paper describes an experimental methodology that permits to evaluate this transition thanks to raw experimental data, and its application to a range of constant but different strain rate and temperature tests performed on the T700GC/M21 CFRP material. KEYWORDS dynamic properties, mechanical properties, non-linear behaviour, polymer-matrix composite, temperature dependency Strain. 2017;53:e12248.wileyonlinelibrary.com/journal/str

The organic matrix composites (OMC) are widely used in aeronautical industry. The mechanical behaviour of these materials is known to be strain rate and temperature dependent. Therefore it is necessary to take the influence of temperature and strain rate into account in the behaviour models. The mechanical behaviour of OMC can be split into two different parts: a first linear and a second non linear phasis. To predict the evolution of the mechanical behaviour, it is important to evaluate the transition between linear and non linear behaviour with respect to the influence of the strain rate and the temperature. For this purpose, different strain rate and temperature dependent failure criteria and yield stress criteria, available in the literature were considered. These criteria were compared to the experimental results obtained in previous works [1]. Finally a strain rate and temperature dependent criterion was proposed to describe more accurately this transition evolution.