Abstract: A method of arresting delamination between and within plies of a composite laminate having layers containing a resin without significantly degrading the structural strength of the laminate characterized by emplacing within a plurality of the laminate layers having a resin, at a plurality of respective discrete locations, narrow strips of a tough adhesive having a fracture toughness greater than the fracture toughness of the resin in the respective layers of laminate. The adhesive has a Mode I critical strain energy release rate in the range of 5 inch pounds per square inch or more; for example, about 10 inch pounds per square inch. Also disclosed is a preferred method of constructing the laminate to employ this invention.

Abstract: A functionally improved tape-like, heterogeneous, strip material for use in the fabrication of laminated structural shapes having high value of Young's Modulus and high tensile strength, comprising collocated, unidirectional, tectonic filaments such as graphite, boron, silicon-carbide, S-glass and E-glass, embodied in planar concourse, into an organic, thermosetting resin matrix or sheath such as an epoxy or polyimide base polymer forming a basal tract having at least one integral marginal tract of differing physical character so that a relatively lower Young's Modulus is exhibited by the material comprising the marginal tract than that exhibited by the basal tract. This difference in structural characteristic serves to provide an inherent arrestment barrier against fast rupture propagation of fractures which may develop in the basal tract material when the composite strip is subjected to sustained overload or external damage.