Chang-Sun Hong

Low-velocity impact damage is a major concern in the design of structures made of advanced laminated composites, because such damage is mostly hidden inside the laminates and cannot be detected by visual inspection. It is necessary to develop the impact monitoring techniques providing on-line diagnostics of smart composite structures susceptible to impacts. In this paper, we discuss the process for impact location detection in which the generated acoustic signals are detected by PZT using the im

In this paper, we present the simultaneous measurement of the strain and temperature during cures of various composite laminates using fiber Bragg grating/extrinsic Fabry-Perot interferometric (FBG/EFPI) hybrid sensors. The characteristic matrix of the hybrid sensor is derived analytically. For the fabrication of the three types of graphite/epoxy composite laminate, two FBG/EFPI hybrid sensors were embedded in each composite laminate in two mutually perpendicular directions. We performed the rea

In this paper, fiber Bragg gratings (FBGs) were applied to measure dynamic strains inside a subscale wing under real-time wind tunnel testing. Two re-coated FBGs were embedded in the wing skin. The FBG sensor system includes a wavelength swept fiber laser with a wavelength indicator and fast signal processing modules. The agreement among the three kinds of sensor inside the subscale wing (FBG, electric strain gauge and PZT sensor) was confirmed in the bench test. The optical fiber strain sensors

In this paper, we present a simultaneous measurement of strain and temperature during and after cure of unsymmetric cross-ply composite laminate using fibre-optic sensors. Fibre Bragg grating/extrinsic Fabry-Perot interferometric (FBG/EFPI) hybrid sensors are used to measure those measurands. The characteristic matrix of the sensor is derived analytically and measurements can be done without sensor calibration experiments. A wavelength-swept fibre laser is utilized as a light source. Two FBG/EFP

This paper presents the simultaneous measurement of strain and temperature using fiber Bragg grating/extrinsic Fabry-Perot interferometric (FBG/EFPI) sensor. This hybrid sensor consists of a FBG element encapsulated in EFPI sensor. Temperature can be measured from FBG part and strain from EFPI. We have analytically derived the relationship of the sensor outputs to measurands (strain and temperature) and yielded the characteristic matrix of sensor. Therefore, it is not necessary to perform sensor

Buckling and postbuckling behaviors were analyzed numerically and experimentally for composite plates with a hole. In the finite element analysis, the updated Lagrangian formulation and the eight-node degenerated shell element were used. For the progressive failure analysis, the maximum stress criterion was applied to the average stress in each layer of all the finite elements and then stiffness and stress corresponding to the failure mode were reduced to zero for the failed layers of all the el

Advanced composites are being extensively used for aerospace structures due to the high stiffness to weight and high strength to weight ratios. Measuring internal strings of composite structures is of great interest with respect to the structural integrity of aerospace structures. A large number of sensors are required for large-scale structures such as aircraft. Fiber Bragg grating (FBG) sensor system based on the wavelength division multiplexing (WDM) technology offers a versatile and powerful