Effects of material and geometric nonlinearities on the tensile and compressive behavior of composite materials with fiber waviness

The effects of fiber waviness on the nonlinear behavior of unidirectional c omposites under tensile and compressive loadings have been investigated the oretically and experimentally. Unidirectional composites examined were comp osed of continuous fibers with sinusoidal waviness in a matrix. As a conseq uence of material and geometric factors, both the tensile and compressive b ehavior of these composites was generally nonlinear under finite deformatio n. Analytical models were proposed for predicting the nonlinear tensile and compressive behavior as a function of fiber waviness for three types of fi ber waviness pattern: uniform, graded and localized fiber waviness. The mat erial and geometric nonlinearities due to fiber waviness were incorporated into the models based on complementary energy density and an incremental me thod. Specimens with various degrees of fiber waviness were fabricated. Ten sile and compressive tests were conducted on the specimens to obtain the el astic properties and behaviors of the composite materials with fiber wavine ss. The experimental results were in good agreement with the predictions. ( C) 2000 Published by Elsevier Science Ltd. All rights reserved.