Experimental evaluation of the elastic limit of carbon‐fibre reinforced epoxy composites under a large range of strain rate and temperature conditions

Abstract

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

A strain rate and temperature dependent criterion to describe the linear - non linear behaviour’s transition of organic matrix composite materials in shear: Application to T700GC/M21

“…To the authors knowledge, the value of the transition between linear and non-linear behaviour is usually characterised by inverse methods for a laminate [±45 • ]. In previous works [1], a direct method to evaluate accurately this transition using only experimental raw data was proposed. In these works, the authors obtained this transition for six different strain rates at ambient temperature and for three different strain rates at −40 • C and −100 • C. This transition is hereafter referred as σ t /ε t .…”

“…In these works, the authors obtained this transition for six different strain rates at ambient temperature and for three different strain rates at −40 • C and −100 • C. This transition is hereafter referred as σ t /ε t . In [1], the strain rate and temperature dependencies of this transition were established. Therefore to take into account this transition in a behaviour model, it is necessary to have a model of this transition which includes temperature and strain rate dependencies.…”

“…These tests were described in more details in [1,18,19]. For each test, the method described in [1] was applied and the transition between the linear and non linear behaviour, σ t and ε t , was characterized. The obtained results are plotted in Figure 1.…”

“…This behaviour once studied, the question arises of the transition between linear and non-linear behaviour. This transition can be evaluated in terms of stress σ t or strain ε t [1].…”

“…For this purpose, an experimental investigation on the T700GC/M21 [±45] laminate for a large range of strain rates and temperatures using an hydraulic jack has been used [17,18]. The σ t and ε t obtained in [1] were considered for modelling purposes. In a first step a strain rate dependent model is proposed.…”