Title: Advanced Green Composites

Authors: Anil Netravali

DOI:

Abstract: Advanced composites made using high strength fibers such as graphite and Kevlar fibers have replaced steel and other metals in many applications from aerospace to sports gear and from satellites to automobiles because of their significantly higher specific strength and stiffness. Both fibers and resins used in these composites are derived from non-sustainable petroleum. They are non-degradable and no environmentally benign way exists to dispose them at the end of their life. Majority of them are dumped in landfills. Green composites, on the other hand are made using fibers and resins that are biodegradable and mostly derived from fully sustainable plants. They can be easily composted. Major research efforts to develop fully green materials that started in the 1990s have made significant progress in developing green composites. Recent development of high strength liquid crystalline cellulosic (LCC) fibers has allowed fabricating ‘advanced green composites’ that have high tensile and flexural properties. As a result, these composites can compete with aramid-based advanced composites and may be used in some primary structural as well as ballistic applications. This paper discusses fabrication of fully degradable advanced green composites, their mechanical properties and possible applications.

References: The global aerospace industry's increasing emphases on lightweight design, fuel efficiency, and cost optimization has accelerated the adoption of advanced composite materials. Assembly gaps from manufacturing tolerances have proven to be a challenge in the use of composite structures. Curable liquid shims eliminate labor intensive, slow placement of solid shims. This paper discusses the next generation liquid shim (NGLS). This shim cures more quickly and incorporates extremely hard, low-coefficient of thermal expansion (CTE) fillers to achieve highperformance. Cure kinetics were evaluated with Differential Scanning Calorimetry (DSC) and Shore D hardness testing throughout the cure. Handleability was characterized by slump and application time. Mechanical properties were evaluated by Tensile Lap Shear (TLS), dogbone tensile strength, and compression testing. To evaluate crack resistance, the liquid shim was thermocycled between −55°C (−67°F) and 177°C (350°F). The NGLS demonstrates significant performance compared to the state-of-the-art liquid shim product, LOCTITE EA 9377. Key improvements include a reduced cure time (from > 9 hours to approximately 6.25 hours), superior thermocycling crack resistance from 121°C to 177°C (250°F to 350°F), and a higher compressive strength from 121 MPa to 184 MPa (17.6 ksi to 26.7 ksi). These results confirm that the NGLS successfully meets the demands for high-manufacturing throughput, improved thermocycling crack resistance, and superior mechanical performance for advanced aerospace structures.

Conference: SAMPE 2026

Publication Date: 2026/04/27

SKU: 250

Pages: 9

Price: $18.00