Fractal interfacial enhancement of composite delamination resistance

A composite structure comprising a first lamina and a second lamina, said first lamina having a first laminal surface which defines a first laminal fractal profile, said second lamina having a second laminal surface which defines a second laminal fractal profile which is complementary with respect to said first laminal fractal profile, said first laminal surface and said second laminal surface being complementarily joined so as to form an interfacial region which defines an interfacial fractal profile which is described by the engagement of said first laminal fractal profile and said second laminal fractal profile, said interfacial region being bounded by said first laminal surface and said second laminal surface, said interfacial fractal profile being bounded by said first laminal fractal profile and said second laminal fractal profile, said interfacial region being at least substantially characterized by longitudinal constancy of said interfacial fractal profile through said interface in an orthogonal direction with respect to an imaginary vertical plane which passes through said first laminal fractal profile, said second laminal fractal profile and said interfacial fractal profile, wherein:

• said composite structure comprises secondary bond material which at least substantially occupies said interfacial region;
• said first laminal surface describes an arrangement of first longitudinal elevations and first longitudinal depressions;
• said second laminal surface describes an arrangement of second longitudinal elevations and second longitudinal depressions;
• said first longitudinal elevations mate with said second longitudinal depressions;
• said second longitudinal elevations mate with said first longitudinal depressions;
• said longitudinal constancy is manifested by said first longitudinal elevations, said first longitudinal depressions, said second longitudinal elevations and said second longitudinal depressions;
• said first lamina includes a first resin and a plurality of first unidirectional fibers which are disposed in said first resin in an orthogonal direction with respect to said imaginary vertical plane;
• said second lamina includes a second resin and a plurality of second unidirectional fibers which are disposed in said second resin in an orthogonal direction with respect to said imaginary vertical plane;
• some said first unidirectional fibers are disposed in said first longitudinal elevations;
• and
• some said second unidirectional fibers are disposed in said second longitudinal elevations.

A matrix composite laminate comprising first and second layers which join so as to form a tortuous interface, wherein:

• said first layer includes plural parallel linear first fibers;
• said second layer includes plural parallel linear second fibers;
• said first and second fibers are parallel to each other;
• said first layer has a tortuous first face;
• said second layer has a tortuous second face;
• said tortuous first face has plural first ridges and plural first grooves which are parallel to each other and to said first and second fibers;
• said tortuous second face has plural second ridges and plural second grooves which are parallel to each other and to said first and second fibers;
• said first ridges, said first grooves, said second ridges and said second grooves are parallel to each other;
• some said first fibers are placed in said first ridges;
• some said second fibers are placed in said second ridges;
• said first face is characterized by a first face fractality which manifests in the direction perpendicular to said first and second ridges and first and second grooves;
• said second face is characterized by a second face fractality which manifests in the direction perpendicular to said first and second ridges and first and second grooves;
• said tortuous interface is characterized by an interface fractality which manifests in the direction perpendicular to said first and second ridges and first and second grooves;
• said first face fractality and said second face fractality are inversely congruent, said first face fractality and said second face fractality thereby meshing with each other, said first face fractality and said second face fractality thereby defining said interface fractality, said first ridges thereby fitting said second grooves, said second ridges thereby fitting said first grooves, said first and second ridges and first and second grooves thereby defining said tortuous interface;
• said first face is characterized by at least approximate linearity which manifests in the direction of said first and second ridges and first and second grooves;
• said second face is characterized by at least approximate linearity which manifests in the direction of said first and second ridges and first and second grooves;
• said tortuous interface is characterized by at least approximate linearity which manifests in the direction of said first and second ridges and first and second grooves;
• said first face fractality manifests approximately identically at at least substantially all locations along said first and second ridges and first and second grooves;
• said second face fractality manifests approximately identically at at least substantially all locations along said first and second ridges and first and second grooves;
• and
• said interface fractality manifests approximately identically at at least substantially all locations along said first and second ridges and first and second grooves.