Drastic Improvements in Bonding of Fiber Reinforced Multifunctional Composites

Achievement of a dramatic increase in the bond strength in the adhesive and composite/adhesive interfaces of existing fiber reinforced composite material joints and structures suitable for various NASA applications is the main goal of this project. The proposed technology developed at Integrated Micro Sensors Inc is based on laser-assisted fabrication of Micro Column Arrays (MCA) on the surface of the two materials prior to bonding. There are several advantages of the MCA technology in the drastic improvement of any bond: (i) mechanical strength increases due to interlocking of the adhesive or brazing material between micro columns, (ii) the bond strength increases due to the increase of the specific surface area by more than an order of magnitude, (iii) stability increases due to the inherent elasticity of the micro cones during a deformation, (iv) increase in the bond durability because of the repeated bend contours of the surface preventing hydrothermal failure, (v) wettability of the material surface significantly improves due to the highly developed surface morphology at the micro and submicron level and changes in local chemistry as a result of surface oxidation. Based on the feasibility proven in the Phase I project, this Phase II project will focus on implementation of the proposed technology for newest materials developed up to date and scaling of the proposed technology to large area and complex shape FRP composite structural joints. The investigation of the approach based on using the bond interface electrical properties for joint health monitoring initiated in the Phase I project, will be further developed into viable transducer device concepts.

The MCA technology is efficient, highly reproducible, environmentally safe, and can be applied virtually to any solid state material. In addition, the MCA technology is highly scalable to large areas and minimum processing times, as the MCA fabrication efficiency is proportional only to the average laser power. Lasers with average powers up to 5 kW are currently commercially available. In addition, precise CNC systems are currently available for providing the MCA fabrication process on curved and complex shape parts. As a result the MCA application range will expand to any area where reliable bonding between to materials is required. Such areas can include medical applications (dentistry and bone surgery), sport gear (golf and hockey clubs, boats), automobile (lighter and stronger parts), etc.

Aerospace applications require novel and reliable material systems and structures to meet the increasing requirements of innovative designs. Lightweight composite materials have a high potential for applications in the areas of increased payload, reduced costs, and better survivability. Subsonic, supersonic, and especially hypersonic thrusts pose an extraordinary challenge for structures and materials. The airframe and engine require lightweight, materials and structural configurations that can withstand the extreme environment of the flight. One of the very important issues in the aerospace industry is bonding of dissimilar materials, since high bond resistance to high and rapid thermal and mechanical loads is required. Composite materials have very different coefficients of thermal expansion. In addition, structural properties and thermal conductivities are different too, which actually adds to the problem. Aerothermic heating, and high mechanical loads caused by ultra-high speeds, is one area of intensive research targeted by the current project.

This is early/mid-stage (TRL 6) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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