MECHANICAL ANALYSIS AND VISCOELASTIC MODELING OF A 3D INTERLOCK WOVEN COMPOSITE

The aim of this work is to study the cure and temperature dependent homogenized viscoelastic model of a composite material reinforced with three dimensional (3D) woven fabrics. First, the linearly viscoelastic behavior of a composite material made of 3D woven interlock fabrics and epoxy resin was experimentally studied. Rectangular composite plates were manufactured by Resin Transfer Molding (RTM). Three configurations were studied as follows to emphasize the future material response: warp tows oriented at 45 degrees from the longitudinal plate direction, and weft and warp tows respectively oriented along the longitudinal plate direction. Creep tests were carried out with a universal testing machine using a tension fixture to study the viscoelastic behavior of the material at high temperatures. Six isothermals were tested from 120 degrees C to 200 degrees C, measuring the viscoelastic response below and above the glass transition temperature, T-g, of the resin. A mathematical modeling of the homogenized viscoelastic properties of the composite was developed in this work based on resin viscoelasticity and fabric geometrical homogenization. Finally, experimental results were compared to the cure and temperature dependent homogenized linear viscoelastic model developed in this work. This model is a step forward for the accurate prediction of the residual stresses development during the manufacturing of 3D woven interlock composites for structural parts.