Flutter Failure Risk Assessment for Damage-Tolerant Composite Aircraft Structures

The primary structure of an unmanned air vehicle (UAV) wing is commonly composed of outer wing skins attached (bonded or fastened) to a main wing spar both composed of advanced composite materials. The main wing spar is designed to take the primary bending and transverse shear loads, whereas the wing skin is designed to take the wing torsion loads. Since these aircraft are developed for long range continuous (surveillance) flight with minimal time for ground inspection, it is desirable to have an in-flight structural health monitoring (SHM) system for insuring the structural integrity of the wing structural components and attachments. In the current study an SHM computational and experimental testbed is developed for analyzing the structural integrity of a composite wing spar, where fixturing is included to produce realistic wing bending and torsion natural frequencies and corresponding coupled bending-torsion vibration modes. The wing spar is instrumented using Bragg graded fiber optic distributed strain sensors along the spar length on three sides to determine the axial strain and bending modal curvature distributions and in a wavy configuration on the fourth side in an attempt to monitor spar twisting behavior. Initially, finite element studies of a damaged composite wing spar are performed to determine the modal curvature distributions for evaluation of numerous published SHM approaches. Finally, an experimental study is performed where the free vibration response of the undamaged and damaged wing spar is monitored based upon either an impact excitation or an initial displacement. While these results clearly show the damage using the computational models, there are difficulties locating damage using the distributed fiber optic strain sensors.

show abstract

“…In the current development, these methods are extended to include the multiple optical fibers (1)(2)(3) …”

Section: C) Damage Index (Di)mentioning

confidence: 99%

“…Flight structures in particular suffer from impact, overload, and fatigue damage, which can then grow internally under cyclic operational loads and overloads to the point of catastrophic failure either by strength exceedance or stiffness degradation leading to dynamic instability (i.e. flutter) [2].…”

Section: Introductionmentioning

confidence: 99%

Detecting Damage in a UAV Composite Wing Spar Using Distributed Fiber Optic Strain Sensors

Martins

Kosmatka

2015

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

View full text Add to dashboard Cite

show abstract

“…; qg. In particular, the wing skin-to-spar adhesive joints are recognized as the most fatigue-sensitive structural elements of a lightweight composite UAV because the progressive debonding, evolving from the wing-root along these joints, can compromise the global aeroelastic performance of the vehicle (Bauchau & Loewy, 1997;Styuart, Demasi, Livne, & Lin, 2008;Styuart, Demasi, Livne, & Mor, 2011;Styuart et al, 2007;Wang, Inman, & Farrar, 2005). All probabilistic information necessary to fully embed and execute this analysis step within the proposed SHM-DP framework are contained in the joint PDF of the load intensity measure vector denoted as f IM (im).…”

Section: Probabilistic Load Hazard Analysismentioning

confidence: 99%

Developing an integrated structural health monitoring and damage prognosis (SHM-DP) framework for predicting the fatigue life of adhesively-bonded composite joints

Gobbato¹,

Kosmatka

Conte

2015

Fatigue and Fracture of Adhesively-Bonded Composite Joints

View full text Add to dashboard Cite

“…Direct MCS is the simplest nonintrusive approach used in relatively simple aeroelastic studies [42][43][44][45][46][47][48][49][50]. This method requires numerous evaluations of the function of interest (e.g., flutter Mach number) at values of the uncertain inputs dictated by their probability distributions.…”

Section: A Characterization Of Input Probability Distributionmentioning

confidence: 99%

Hypersonic Aeroelastic and Aerothermoelastic Studies Using Computational Fluid Dynamics

Lamorte

Friedmann

2014

AIAA Journal

View full text Add to dashboard Cite

A framework for aerothermoelastic-stability-boundary calculation for hypersonic configurations using computational fluid dynamics combined with radial basis functions for mesh deformation is developed. Application of computational fluid dynamics enables one to consider different turbulence conditions, laminar or turbulent, and different models of the air mixture, in particular real-gas model, which accounts for dissociation of molecules at high temperature. The effect of transition on the flutter margin of the heated structure is also considered using an uncertainty-propagation framework. The aerothermoelastic-stability margin of a three-dimensional low-aspect-ratio wing, representative of a control surface of a hypersonic vehicle, is investigated for various flight conditions. The system is found to be sensitive to turbulence modeling, as well as the location of the transition from laminar to turbulent flow. Real-gas effects play a minor role for the flight conditions considered. This study demonstrates the advantages of accounting for uncertainty at an early stage of the analysis, and emphasizes the important relation between transition from laminar to turbulent, thermal stresses, and stability margins of hypersonic vehicles.

show abstract

Flutter Failure Risk Assessment for Damage-Tolerant Composite Aircraft Structures

Cited by 17 publications

References 18 publications

Detecting Damage in a UAV Composite Wing Spar Using Distributed Fiber Optic Strain Sensors

Detecting Damage in a UAV Composite Wing Spar Using Distributed Fiber Optic Strain Sensors

Developing an integrated structural health monitoring and damage prognosis (SHM-DP) framework for predicting the fatigue life of adhesively-bonded composite joints

Hypersonic Aeroelastic and Aerothermoelastic Studies Using Computational Fluid Dynamics

Contact Info

Product

Resources

About