Effective moduli and failure considerations for composites with periodic fiber waviness

A finite element micromechanical model for fibrous materials introduced in a previous work [J. Compos. Mater. 38 (4) (2004) 273] is used to further study the effects of periodic and localized fiber waviness. A periodic unit cell based on hexagonal fiber packing and sinusoidal fiber waviness was assumed as a representative volume element. Equivalent to this wavy-shaped unit cell, a straight unit cell but with wavy material-orientation is introduced. This type of homogenized continuum modeling simplifies the analysis since the wavy geometry with details of constituent materials is avoided. Thus, stiffness parameters associated with individual lamina with waviness are estimated when subject to the constraining effects of neighboring isotropic or straight fiber material layers. It is shown that the shear constraint of the added layers increases the effective moduli of the wavy layer by inhibiting the fiber straightening deformation mechanism. The local stress distribution is also examined and the potential for material failure is investigated. The methodology provides a platform to study the behavior of wavy fiber composites in a systematic manner.