Modeling the nonlinear deformation of flax-fiber-reinforced polymer matrix laminates in active loading

In an attempt to fully utilize the mechanical properties of bast fibers in polymer-matrix composites, unidirectional (UD) or quasi-UD flax-fiber-reinforced composites are being developed and characterized. Their response in tension is markedly nonlinear both in on- and off-axis loading. A semiempirical tensor-linear model is applied to describe such deformation nonlinearity in active combined loading. The deformation model of UD ply, combined with an elementary laminate theory, is used to predict the stress-strain curves of laminated composites in tension. Reasonable accuracy of prediction is demonstrated for fiber-dominated layups.