Abstract: Portable shadow moire apparatus is disclosed for indiscriminately manipulng the grid and light source thereof over a specimen surface, with the grid oriented substantially in parallel therewith and in close proximity thereto. Self aligning support is provided on such apparatus, along with height adjustability for that support. Utilization of very high density grids is made possible by such apparatus to enhance the detection sensitivity thereof. Light source direction variability is also provided to control the magnitude of detectable distortion.

Abstract: An apparatus is disclosed for remotely detecting cracks of sub-critical lth which originate from stress raisers in structural materials, wherein the apparatus typically comprises a source of light, a continuous length of optical fiber to conduct the light, strain responsive devices coupled to the fiber and bonded to the structural member in close proximity to the stress raisers, and a light responsive detector which is optically coupled to the fiber in order to detect breaks in the fiber induced by either tensile or shear forces eminating from cracks around the stress raisers.

Abstract: Interlaminar shear strength of an aircraft wing made of graphite-epoxy laate is significantly increased by embedding thin steel wires in preselected locations of high stress in alternating rows .+-.45.degree. to the plane of the laminate before it is cured. This cross wire reinforcement prevents brittle delamination, arrests propagation of delamination and reduces scatter of interlaminar strength.