The purpose of this paper is to investigate the mechanical behavior of fiber-reinforced incompressible nonlinearly elastic solids under large simple shear deformations. Two different rubberlike materials, with distinct properties of adhesion, were reinforced by a single family of parallel fibers of nylon. Fibers of nylon 6 monofilament fishing line with diameters of 0.25, 0.45, and 0.80 mm were used. Fiber-reinforced specimens were tested under monotonic load at constant temperature, and values of amount of shear were obtained by the digital image correlation method. A phenomenological constitutive model is proposed to predict the mechanical behavior of the transversely isotropic materials. The proposed model takes into account the shear and stretch in the fiber, and fiber-matrix iterations. These iterations are related to the quality of the fiber-matrix bonding and fibers pullout. The obtained results can be useful in understanding the mechanical behavior of fiber-reinforced rubberlike solids and fibrous soft tissues.

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A simple model for describing the mechanical behavior of a soft bidirectional-fiber-reinforced composite under simple shear deformation is proposed. Four parameters, including material properties and initial angle of fibers, are required in this model to predict the nonlinear material response. A soft material that was made of silicone rubber and two families of continuous fibers of polypropylene were tested in order to validate the proposed model. Experiments were performed on composite specimens with two distinct fiber orientations. The values of shear strain were evaluated from full-field displacements extracted by the digital image correlation method. The properties of the fibers and the neat matrix were obtained from uniaxial tensile and simple shear tests, respectively. These data were used as input data. The model predictions are in excellent agreement with the experimental data of the elastomeric composite. After validation, the proposed model was used to characterize the shear response of an annulus fibrosus of ovine intervertebral disk, using experimental data from literature. The results indicate that the proposed model is capable of describing the nonlinear response of the annulus fibrosus under simple shear. Moreover, it may be suitable for estimating important mechanical parameters of fibrous soft tissues.