Composite structures with damage detection capability

A method for detecting damage in a polymer-matrix fiber-reinforced composite structure, the structure comprising a plurality of layers each comprising a polymer-matrix composite, the plurality of layers comprising a first layer, wherein the first layer comprises a first polymer-matrix and a first fluorescent agent interspersed through the first polymer-matrix, the structure being configured such that damage to one of the layers results in a change in fluorescence observable from the at least first layer at the point of damage, the method comprising:

• applying light having a wavelength selected to induce fluorescence in the first fluorescent agent to the polymer-matrix fiber-reinforced composite structure;
• detecting a detected fluorescence pattern;
• and
• comparing the detected fluorescence pattern to a predetermined normal fluorescence pattern without damage.

A method for making a polymer-matrix fiber-reinforced composite structure, the structure comprising a plurality of layers each comprising a polymer-matrix composite, the plurality of layers comprising a first layer, wherein the first layer comprises a first polymer-matrix and a first fluorescent agent interspersed through the first polymer-matrix, the structure being configured such that damage to one of the layers results in a change in fluorescence observable from the at least first layer at the point of damage, the method comprising:

• providing a polymer;
• mixing the first fluorescent agent into the polymer to form a fluorescent-based polymer;
• arranging a layup using the fluorescent-based polymer;
• and
• making the polymer-matrix fiber-reinforced composite structure by curing or solidifying the layup;
• wherein the first fluorescent agent is interspersed throughout the first polymer-matrix.