Compressive Damage in Three-Axis Woven Thermoplastic Composites

Abstract

This work examines compression-induced damage in a three-dimensional woven carbon/Nylon 6 composite. A carbon yarn commingled with Nylon 6 powder was used to make the woven fabric, which has a 3-axis orthogonal yarn structure in the interior. The fabric was hot-pressed along the thickness direction to form the three-dimensional thermoplastic composites. A matched mold was designed for hot-pressing the composites into a fixed thickness. The influence of the molding temperature on the compressive strength was studied. The compressive tests were conducted using an end-supported, end-loaded fixture. The induced damage modes inside the composite were observed. The major mode of damage is a miniscopic kink-band, in which axial yarns tend to buckle as a whole. The miniscopic kink-band contains a number of smaller modes of damage, such as microscopic fiber buckling, yarn deflection, yarn debonding, yarn split, and shear deformation in transverse yarns. The miniscopic kink-band is inclined at 45° to the loading direction, suggesting that the compression-induced, through-thickness shear is the cause of failure. Even under excessive strain, the specimen showed no breaking apart and was still able to resist the load. The roles of the through-thickness yarns and the 3D structure in the damage mechanisms are discussed.

Keywords

3D composite compressive damage thermoplastic composites

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