Mechanical properties of interfaces within a flax bundle – Part I: Experimental analysis

In order to model the tensile behaviour of flax fibre based composites, the properties of each of the constituents need to be determined. In addition to the fibres, the matrix and the fibre/matrix interface, the fibre/fibre interface present within a bundle of flax fibres is an element which is rather hard to characterize but whose properties also need to be taken into account to understand properly the deformation and rupture modes of the derived composites. In the first part of this study, the protocol used to determine these properties is described; the results of the mechanical tests and the microscopic observations carried out on pairs of fibres are given and exploited to lead to the fibre/fibre interface properties. In the second part, various cohesive zone models will be evaluated using these interface properties and numerical simulations will be performed for the purpose of validation.