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