• Journal of Aerospace System Engineering
• /
• v.7 no.1
• /
• pp.39-43
• /
• 2013

In this study, damage assesment and repair technique of aircraft adopted on Sandwich composite structure were performed. The sandwich composite structure were damaged by drop weight type impact test machine. The damaged sandwich composite structure was repaired using external patch repair method after removing damaged area. This study presents comparison results of the experimental investigation between the impact damaged and the repaired specimen.

• The Journal of the Korean dental association
• /
• v.55 no.10
• /
• pp.676-687
• /
• 2017

Objectives : The aim of this study was to evaluate the effects of a composite of bone substitute and collagen barrier membrane (bone patch) for local ridge augmentation at peri-implant dehiscence defects on the clinical efficacy and positional stability in dogs. Materials and methods : Implant placement and ridge augmentation procedure were performed at surgically created peri-implant dehiscence defects in canine mandible (n=6). Four treatment modalities were randomly applied: i) bone patch group, ii) Guided bone regeneration (GBR) without pin fixation group (bone graft and collagen membrane), iii) GBR with pin fixation group, and iv) negative control group. After 12 weeks, clinical, micro-CT and histological analyses were performed. Results : Histologic analysis showed that bone patch group had similar results to GBR group and GBR with fixation group in terms of new bone formation. Micro-CT analysis revealed similar results to histologic analysis in terms of total volume maintenance. Operating time was shorter in bone patch group compared to GBR group and GBR with fixation groups. Conclusions : GBR using bone patch could simplify the ridge augmentation procedure with reduced operating time and equivalent biological performance compared to the conventional procedure.

• Advances in aircraft and spacecraft science
• /
• v.10 no.4
• /
• pp.335-346
• /
• 2023

In this study, The Von Mises stresses in composite plate loaded in tension and repaired by a boron/epoxy scarf patch were analyzed using the finite element method. The performance of the repairs depends on several parameters: the dimensions and the intrinsic properties of the patch and the adhesive which are dependent on each other. Therefore, the method of experiment designs is used to determine the interaction effect of different parameters (patch folds), their optimum and the most influential parameter. The optimum of stacking sequences allows reducing stresses significantly, and thus permits designers to improve the quality of repairs.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.12
• /
• pp.967-974
• /
• 2013

Recently the authors had proposed the z-pinning patch concept to simply manufacture z-pinned composite structures at industrial production site and manufactured composite single-lap shear joint specimens using the concept. Through static tensile test on the specimens they had obtained 54~68% improvement of the joint strength. As a sequential study of it, in this study, fatigue test has performed to measure an improvement of joint strength under cyclic loading. The z-pin's material is stainless steel and its surface was specially machined into zagged shapes and chemically corroded to increase the connection force with composite materials. Approximately 98~125% improvement of the joint strength under cyclic loading was obtained.

• International Journal of Aeronautical and Space Sciences
• /
• v.6 no.1
• /
• pp.17-26
• /
• 2005

An optical phase tracking technique for an extrinsic Fabry-Perot interferometer (EFPI) is proposed in order to overcome interferometric non-linearity. Basic idea is utilizing strain-rate information, which cannot be easily obtained from an EFPI sensor itself. The proposed phase tracking system consists of a patch-type EFPI sensor and a simple on-line phase tracking logic. The patch-type EFPI sensor comprises an EFPI and a piezoelectric patch. An EFPI sensor itself has non-linear behavior due to the interferometric characteristics, and a piezoelectric material has hysteresis. However, the composed patch-type EFPI sensor system overcomes the problems that can arise when they are used individually. The dynamic characteristics of the proposed phase tracking system were investigated, and then the patch-type EFPI sensor system was applied to the active suppression of flutter, dynamic aeroelastic instability, of a swept-back composite plate structure. The proposed system has effectively reduced the amplitude of the flutter mode, and increased flutter speed.

• Structural Engineering and Mechanics
• /
• v.17 no.3_4
• /
• pp.347-356
• /
• 2004

In order to extend the lifetime of buildings and civil infrastructure, patch type fibrous composite retrofitting materials are widely used. Retrofitted concrete columns and beams gain stiffness and strength, but lose toughness and show brittle failure. Usually, the cracks in concrete structures are visible to the naked eye and the status of the structure in the life cycle is estimated through visual inspections. After retrofitting of the structure, crack visibility is blocked by retrofitted composite materials. Therefore, structural monitoring after retrofitting is indispensable and self diagnosis method with optical fiber sensors is very useful. In this paper, we try to detect the peel out effect and find the strain difference between the main structure and retrofitting patch material when they separate from each other. In the experiment, two fiber optic Bragg grating sensors are applied to the main concrete structure and the patching material separately at the same position. The sensors show coincident behaviors at the initial loading, but different behaviors after a certain load. The test results show the possibility of optical fiber sensor monitoring of beam structures retrofitted by the composite patches.

• Steel and Composite Structures
• /
• v.29 no.3
• /
• pp.309-318
• /
• 2018

Steel girders are the structural members often used for passing long spans. Mostly being subjected to patch loading, or concentrated loading, steel girders are likely to face sudden deformation or damage e.g., web breathing. Horizontal or vertical stiffeners are employed to overcome this phenomenon. This study aims at assessing the feasibility of a machine learning method, namely the support vector machines (SVM) in predicting the patch loading resistance of longitudinally stiffened webs. A database consisting of 162 test data is utilized to develop SVM models and the model with best performance is selected for further inspection. Existing formulations proposed by other researchers are also investigated for comparison. BS5400 and other existing models (model I, model II and model III) appear to yield underestimated predictions with a large scatter; i.e., mean experimental-to-predicted ratios of 1.517, 1.092, 1.155 and 1.256, respectively; whereas the selected SVM model has high prediction accuracy with significantly less scatter. Robust nature and accurate predictions of SVM confirms its feasibility of potential use in solving complex engineering problems.

• Steel and Composite Structures
• /
• v.49 no.4
• /
• pp.419-430
• /
• 2023

This paper is aimed at investigating the effect of multiple longitudinal stiffeners on the patch loading resistance of slender steel plate girders. Firstly, a numerical study is conducted through geometrically and materially nonlinear analysis with imperfections included (GMNIA), the model is validated with experimental results taken from the literature. The structural responses of girders with multiple longitudinal stiffeners are compared to the one of girders with a single longitudinal stiffener. Thereafter, a patch loading resistance model is developed through machine learning (ML) using symbolic regression (SR). An extensive numerical dataset covering a wide range of bridge girder geometries is employed to fit the resistance model using SR. Finally, the performance of the SR prediction model is evaluated by comparison of the resistances predicted using available formulae from the literature.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.29 no.6
• /
• pp.525-533
• /
• 2009

Emphasis in the paper is placed on describing guided wave successes and challenges for applications in aircraft and composite materials inspection. Guided wave imaging methods discussed includes line of sight, tomography, guided wave C-scan, phased array, and ultrasonic vibration methods. Applications outlined encircles lap splice, bonded repair patch, fuselage corrosion, water loaded structures, delamination, and ice detection and de-icing of various structures.

• International Journal of Aeronautical and Space Sciences
• /
• v.14 no.2
• /
• pp.146-151
• /
• 2013

Carbon nanofibers (CNFs) are electrically conductive. When CNFs are used as fillers in resin, this electrical conductivity can be yielded without adversely affecting the mechanical properties of the resin. When an elastomer is adopted as the resin, a conductive elastomer can then be produced. Due to its flexibility and conductive properties, a large strain sensor based on changes in resistivity may be produced, for strain sensing in flexible structures. In this study, a patch-type large strain sensor using resistivity change in a CNF/elastomer composite was proposed. The measurement limits of the sensor were investigated experimentally, and the limit was found to be 40%, which greatly exceeded the limits of conventional metal-foiled strain gages. Also, the proposed CNF/elastomer large strain sensor can be used to measure flexible materials, while conventional strain gages cannot be used to measure such strains.