Effect of areal weight and chemical treatment on the mechanical properties of bidirectional flax fabrics reinforced composites

In this paper several bidirectional flax fibers, usually used to made curtains, were employed as reinforcement of an epoxy matrix. Four different laminates were made by a vacuum bagging process, with varying both the areal weight and the treatment of the fabric. These structures were mechanically investigated carrying out both tensile and three point flexural tests. In order to evaluate the effect of the identified variables on the mechanical parameters (i.e. Young modulus and maximum stress) a statistical analysis was performed. Finally, by comparing the flax composite with a glass one, the convenience of the replacement of glass fiber was investigated in term of cost, weight and mechanical performances, by evaluating the structural efficiency coefficient of the cost of the material. The presence of layers with different areal weight within the structure induced a significant worsening of the flexural properties, with the start of cracks that produced a delamination failure. Also the tensile modulus got worse. Whereas the treatment on the fibers always improved the mechanical properties because the treated layer showed a behaviour of a pre-impregnated structure. For flexural stresses, the cost analysis was favourable to the substitution of the glass fibers with the flax ones. From this study, the composites reinforced with flax fibers could be used in several fields, as marine or automotive.