Mr. Celestine Kelah Wakha Profile

Celestine Kelah Wakha

at Univ of Maryland College Park

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Author

Publications (2)

Proceedings Article | 19 May 2005 Paper

A smart composite patch for the repair of aircraft structures

Kelah Wakha, Paul Samuel, Darryll Pines

Proceedings Volume 5767, (2005) https://doi.org/10.1117/12.600532

KEYWORDS: Sensors, Composites, Aluminum, Finite element methods, Aerospace engineering, Chemical elements, Actuators, Smart sensors, Aircraft structures, Nondestructive evaluation

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Recent interest in bonded composite patch repair technology for aerospace systems is because this method can be carried out at a reduced cost and time and can easily be applied to complex geometric structures. This paper details the development of a dual stiffness/energy sensor for monitoring the integrity of a composite patch used to repair an aluminum structural component. The smart sensor has the ability to predict the elastic field of a given host structure based on the strain state of two sub-sensors integrated into the structure. The present study shows the possibility of using the sensor to deduce the local instantaneous host stiffness. Damaged structures are characterized by a reduction in their elastic stiffness that evolve from microstructural defects. A local smart sensor can be developed to sense the local average properties on a host. In this paper, sensors are attached to a structure and a modified Eshelby's equivalent inclusion method is used to derive the elastic properties of the host. An analytical derivation and a sensitivity analysis for the quasistatic application is given in a papers by Majed, Dasgupta, Kelah and Pines. A summary of the derivation of the dynamic Eshelby tensor is presented. This is of importance because damage detection in structures undergoing vibratory and other motions present a greater challenge than those in quasistatic motion. An in-situ health monitoring active sensor system for a real structure (an aluminum plate with an attached repair patch) under close-to real lifecycle loading conditions is developed. The detection of the onset of any damage to the structure as well as the repair patch and the subsequent monitoring of the growth of this damage constitute important goals of the system. Both experimental and finite element methods were applied. Experimental results are presented for tests of the aluminum plate with the repair patch under monotonic quasi-static and dynamic loading vibratory conditions. In summary, the study shows that smart bonded composite repair patches are very effective in the repair of thin aluminum structures since they are able to determine the integrity of the repair structure as well as the repair patch.

Proceedings Article | 5 August 2003 Paper

Multifunctional piezoelectric stiffness/energy sensor for monitoring the health of structures

Kelah Wakha, Majeed Majed, Abhijit Dasgupta, Darryll Pines

Proceedings Volume 5056, (2003) https://doi.org/10.1117/12.483465

KEYWORDS: Sensors, Ferroelectric materials, Aluminum, Finite element methods, Diagnostics, Active sensors, Chemical elements, Solids, Structural health monitoring, Aerospace engineering

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