Effect of fiber waviness on stiffness and strength reduction of unidirectional composites under compressive loading

An investigation has been conducted of the effect of fiber waviness on stiffness and strength reduction of unidirectional composites under compressive loading. Analytical models have been developed for determining the elastic properties and compressive strength as a function of fiber waviness for three types of wavy patterns: uniform, graded and localized waviness. Compression tests were conducted to verify the predictions. Experimental results were in good agreement with predictions based on the analytical models. It is shown that in unidirectional composites both major Young's modulus and compressive strength are degraded seriously with increasing fiber waviness. Material anisotropy is also shown to influence the degree of stiffness and strength reduction. Interlaminar shear failure was found to be the dominant failure mechanism for unidirectional wavy composites under compressive loading.