In this project, the through-thickness or interlaminar properties of woven composite materials were investigated under tensile and compressive loading conditions. Experiments were conducted on three thick composite materials consisting of a) 3K twill carbon fibers, b) 12K twill carbon fibers and c) 8HS-7781 satin glass fibers impregnated with an epoxy resin. Tensile and compressive properties such as modulus, strength and strain to failure were determined as well as their corresponding failure modes. For deeper understanding of the damage mechanisms, a full field high-resolution digital image correlation system was used. Clear formations of global strain as well as strain concentrations were identified. Strain levels were also associated with corresponding failure modes. Following this, low magnification optical microscopy analysis was performed on the fracture surfaces. Here, failure mechanisms such as fiber/matrix interface debonding and matrix resin fracture were revealed. Such properties proved to be vital to accurately model the mechanical behavior of lightweight composite structures subjected to three-dimensional state of stresses.
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