| Effects of periodic fiber waviness on the compression strength of unidirectional composites were investigated. A fabrication method for constructing idealized unidirectional glass/epoxy composites containing uniform fiber waviness was developed and static compression testing was performed. Additionally, a progressive damage micromechanics model incorporating constituent-specific failure criteria was used to predict the experimentally determined strengths through the use of fiber, matrix, and interface failure criteria. With the severity of fiber waviness reaching levels typically found in woven composites, compression strength dropped by over 50%; however, greater severities of waviness than typically found in woven composites did not cause any further significant drops in strength. Specimens with much less pronounced fiber waviness still exhibited strength reductions of nearly 25%. The progressive damage prediction results were within 7.2% of actual data on average and deviated at most by 16.6%. Compression failures in the wavy fiber specimens originated at the fiber/matrix interface in regions subjected to high interfacial shear stresses which was in agreement with the finite-element predictions. Results suggest that a well-defined relationship exists between compression strength and fiber waviness and that the fiber/matrix interface plays a key role in determining the compression strength of such composites. |
