System and method for characterizing the equibiaxial compressive strength of 2D woven composites

A method for method for determining equibiaxial compressive strength in a woven composite comprising:

• (i) providing a 2D woven composite specimen on a support ring, the 2D woven composite specimen comprising multiple layers and comprising:
• a top surface and a bottom surface, the bottom surface of the 2D woven composite specimen in contact with the support ring,
• a first set of fibers disposed in a first fiber direction and a second set of fibers disposed in a second fiber direction, the first set of fibers and the second set of fibers interlaced at an angle of 90°,
• a first fiber elastic modulus measured along the first fiber direction, a second fiber elastic modulus measured along the second fiber direction, and optionally at least one additional elastic modulus measured along a direction other than the first fiber direction or second fiber direction, wherein the first fiber elastic modulus and the second fiber elastic modulus are each independently greater than the at least one additional elastic modulus, and wherein the 2D woven composite specimen comprises a tensile strength and a uniaxial compressive strength, the tensile strength greater than the unaxial compressive strength, and
• a matrix in which the first set of fibers and the second set of fibers are embedded, the matrix comprising a matrix elastic modulus, the first fiber elastic modulus and the second fiber elastic modulus each individually greater than the matrix modulus, the bottom surface of the 2D woven composite specimen in contact with the support ring;
• (ii) measuring a first strain with a first strain gauge operatively connected to the bottom surface in a configuration that is parallel to the first fiber direction, and measuring a second strain with a second strain gauge operatively connected to the bottom surface in a configuration that is parallel to the second fiber direction;
• (iii) applying an out-of-plane uniaxial load to the center of the 2D woven composite specimen by contacting a loading ring to the to the top surface of the woven composite specimen under montonic force to induce biaxial flexure in the 2D woven composite until at least a portion of the top surface of the woven composite specimen develops at least one visible crack or until the first and second strain measurements diverge, the loading ring having a diameter less than the diameter of the support ring and disposed concentric to the support ring;
• (iv) obtaining strain measurements on the 2D woven composite specimen from the first and second strain gauges during step (iii);
• and
• (v) determining the equibiaxial compressive strength of the woven composite specimen from stresses calculated from the strain measurements obtained along the first fiber direction and along the second fiber direction.