Effect of variable fiber volume fraction on the elastic properties of wrinkled composite laminates with a micromechanics modeling approach

Laminated polymer composites are used extensively in the automotive and aerospace industries due to their high stiffness and strength-to-weight ratios. Although these composites have become a key enabler in engineering design, this material system is prone to developing out-of-plane wrinkles in its internal layers during layup and/or resin curing, which may severely degrade critical material properties, such as elastic modulus and strength. As the fibers within the composite structure take on internal waviness patterns, the distance between layers may change depending on the profile of the wrinkle, which affects local elastic properties due to the resulting spatially varying non-uniform fiber volume fraction. The aim of this work is to investigate how this phenomenon affects the homogenized properties of a wrinkled composite layup. Our approach uses the Rule of Mixtures, Chamis, Halpin-Tsai, Bridging, and Vignoli-Savi-Pacheco-Kalamkarov micromechanics models to estimate laminate orthotropic elastic properties from its constituents via modifications to Takeda’s analytical homogenization procedure. The goal is to quantify the change in homogenized elastic properties as the local volume fraction varies due to waviness within a laminated composite panel, ultimately increasing safety and reliability for vehicles and other applications that may employ laminated composites.