overview

A lightning strike is a naturally occurring, high voltage, high current, transient electric discharge that can raise local temperatures to 30,000 K at the attachment point over 50–200 μs time scales. Such high temperatures can severely damage aircraft composite structures directly and indirectly near the attachment. In addition, dynamic mechanical pressure loads due to lightning arc channel expansion, arc magneto-hydrodynamic effects, and internal current flow can produce significant amounts of mechanical damage to CFRP composite structures. This project has been performed to characterize composite's lightning damage resistance and developed computational modeling frameworks to predict lightning thermal/mechanical damage to aircraft composite structures.

Carbon fiber-reinforced polymeric (CFRP) composites are widely employed in lightweight and high performance applications. The low thermal endurance of the matrix materials remains a critical problem for use in high temperature applications. In this project, we are currently developing ceramic-based thermal barrier coating (TBC) for aerospace composites. Preliminary study indicated that, using a 1.45-mm thick TBC protected the CFRP substrate can reduce CFRP surface temperature by 300-500°C. With this thin TBC layer, the pristine flexural strength of the TBC/CFRP composite was still preserved, whereas that of neat CFRP was reduced significantly by 95%. Various low temperature TBC for fire-fighting drones, operating 500-1000°C, and high temperature TBC for CFRP composites, withstanding 1500–2500°C, are current under investigated. This project is performed in collaboration with Korea Institute of Science and Technology (KIST), South Korea. 

In this project, a comprehensive literature review on manufacturing defects in filament-wound composite lattice structures is performed. The maximum allowable size, frequency, and volume of each manufacturing defect are presented. Starting with a brief overview of composite lattice structures, various non-destructive test (NDT) methods used to assess various internal or near-surface defects in lattice structures are first discussed. The manufacturing defects considered herein include fiber/tow misalignment (i.e., gaps, overlaps, fiber waviness, twisted tows, and bridging), void, and delamination. The effects of the manufacturing effects on various mechanical properties of both filament wound lattice and laminated composite structures are also thoroughly characterized. 

The thermo-elastic response of aerospace structures is significantly influenced by structural nonlinearities and conventional design tools based on assumption of linearity prove to be insufficient. A nonlinear analysis of the thermoelastic response of aerospace structures opens up the possibility to capture the rich bifurcation behaviour of such panels. The primary objective of this research is to study the impact of non-linearity and local geometric features, particularly corrugations, on the thermo-elastic response and bifurcation characteristics of a hat-stiffened panel. The study derives its motivation from the SR-71 Blackbird that was designed with corrugations in the upper and lower wing skins. 

We aim to develop a novel finite element (FE) model to predict the low-velocity-impact (LVI) and compression-after-impact (CAI) responses of woven carbon fibre/epoxy composites, addressing intra-laminar damage and inter-laminar delamination. First, several LVI tests were performed to introduce initial damages on the composites. CAI tests were then conducted to evaluate the residual compressive strengths of the CFRP composites. Primary damage modes were identified using microscopic observation. Finally, the effects of impactor diameter and impact energy on the LVI response and CAI strength of woven carbon/epoxy laminates were obtained together with discussion of failure mechanism and analyzed using an artificial neural network (ANN). This project is performed in collaboration with Tongji University, China.

Pitch-derived carbon fibers (PCFs) exhibit promising superior thermal and electrical conductivities that make them used in ultra-high temperature thermal applications (2000-3000°C ). In this project, we aim to develop lab-scale and pilot-scale manufacturing process for low-cost PCFs using coal or petroleum precursors. Several manufacturing parameters have been optimized to improve PCF conversion yield and maintain acceptable combined mechanical/thermal/electrical properties. Using as-prepared PCFs, carbon-carbon (C/C) composites are manufactured and their process-structure-property relationship is identified to design ultra-high temperature thermal applications. 

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