JEC COMPOSITES MAGAZINE - Issue #35 - September 2007 - 63

KNOW-HOW Testing Non-destructive evaluation of lightweight nanoscale structural parts for space satellite vehicles The development of novel multi-functional nanoscale structural materials with higher strength-to-weight or stiffness-to-weight ratios and the related technological processes is a significant problem in space communication technology. The prediction of lattice structural stiffness and strength using non-destructive methods is the subject of this article. NASA’s Marshall Space Flight Center (MSFC) has tested Raytheon’s Radiance infrared camera to devise non-destructive evaluation (NDE) methods for assembling the Space Shuttle and other aerospace components. BY YOSIF GOLFMAN, New R & D Programs & Proposals Neo-Advent Technologies, LLC USA 100 and 140 μm. By combining boron fibre with graphite prepreg, a high-performance material with exceptional mechanical properties – the Hy-Bor laminate – was produced (Table 1). Mechanical properties Tensile strength Tensile modulus Values 1,896 MPA 241 GPA 2,413 MPA 214 GPA 2,756 MPA 241 GPA 103 MPA 0.86% 117 MPA N ew nanoscale hybrid materials can provide engineers and spacecraft designers with a super lightweight material, with superior stiffness and strength, near-zero coefficients of thermal expansion (CTE), and minimal micro-cracking. Recently, boron fibres also gained significant recognition as a way to improve mechanical properties. Hybrid carbon-boron/cyanate ester hybrid prepregs have already been successfully tested in space structures. Flexural strength Flexural modulus Compression strength Compression modulus Interlaminar shear strength Strain Short-beam shear strength Table 1: Mechanical properties of the Hy-Bor laminate Advantages of carbon/boron nanoscale fibres The dynamic behaviour of nanoscale carbon fibre/boron structures used in the manufacture of carbon fibre-epoxy composites for launch vehicle interstate structures has been investigated. The deposition mechanism of boron, carbon and silicon was described in a publication. Silicon and boron form a stronger bond than carbon and boron, so the silicon-boron bond is 1.5 times stronger than the carbon-boron bond.We demonstrated that carbon fibres encapsulated by deposits of core glass silica and germanium can be reinforced by boron fibres in the vapour deposition process where borane (BH3) reacts with glass silica (SiCl4) to form silicon-boron filaments on the nanoscale level. Boron fibres have twice the stiffness and five times the strength of steel. Boron fibres are typically made using the chemical vapour-deposition process and precipitate onto a fine tungsten or carbon filament. The resulting boron fibre is strong, stiff, lightweight, and possesses excellent compressive properties and buckling resistance. For example, Special Materials Inc. uses chemical vapour deposition (CVD) for creating boron layers. The process uses fine tungsten wire for the substrate and boron trichloride gas as the boron source. The manufacturing process is precisely controlled and constantly monitored to ensure consistent production of boron filaments with diameters of Other types of materials, such as low thermal conductivity ceramics, can offer advantages for protective coatings of satellites. Thermal barrier coatings (TBC) have thin ceramic layers that are generally applied by plasma spraying or by physical vapour deposition and are used to insulate air-cooled metallic components from hot gases in gas turbines and other heat engines. The ceramic layer consists of 95.4% ZrO2 and 4.6 % Y2O3. However, these coatings have porous, micro-cracked structures. Recently, scandium was identified as a stabilizer that could be used in addition to yttrium. A composition of 3% scandium and 2.5% yttrium may confer the desired phase stability at 1400ºC. Non-destructive evaluation techniques The materials offering a perfect combination of high modulus/strength and low coefficient of thermal expansion combined with a reduced structural weight are the most desirable composites to address space flight requirements. JEC Composites Magazine / No35 September 2007

JEC COMPOSITES MAGAZINE - Issue #35 - September 2007

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #35 - September 2007