Effect of fiber waviness on the bending behavior of S-glass/epoxy composites

A study was conducted on the influence of localized ply waviness on the strength of uniaxial fiberglass composites subjected to three-point bending. A series of experimental three-point bending tests were performed to discover how wave geometry will affect the strength of these materials. It is shown that any waviness will decrease the strength, but this reduction is maximized by increased amplitude, deceased wavelength, and concave up waves as well as increased total specimen length. As much as 37% reduction in strength compared to a flat specimen is seen in the case of large concave up waves. The dominant failure mode for unidirectional wavy composites under bending was shown to be interlaminar shear, which in turn leads to microbuckling. Finally, a failure criterion is derived which can predict the load and location where failure will begin.

► Large concave up waves provide a reduction in bending strength compared to specimens with no waves.
► Small and medium concave down waves provide greater strength than those with large or no waves.
► A failure criterion was developed which includes the component strengths, volume fractions and geometry.
► Failure initiated at the resin pocket for all samples considered herein.
► The dominant failure mode was microbuckling preceded by interlaminar shear and delamination.