Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Nondestructive evaluation (6)
- Aerospace Engineering (5)
- QNDE (5)
- Blades (3)
- Composite materials (3)
-
- Wind turbines (3)
- Finite element analysis (2)
- Fracture (2)
- Inspection (2)
- Plates (structures) (2)
- Adhesive bonding (1)
- Air coupled ultrasonics (1)
- Composites (1)
- Compressive strength (1)
- Condition monitoring (1)
- Cracks (1)
- Data acquisition (1)
- Delamination (1)
- Fatigue testing (1)
- Fiber waviness (1)
- Glass (1)
- Helicopters (1)
- Nondestructive testing (1)
- Optimisation (1)
- Rayleigh waves (1)
- Resins (1)
- Rotors (1)
- Structural engineering (1)
- Ultrasonic applications (1)
- Ultrasonics (1)
- File Type
Articles 1 - 7 of 7
Full-Text Articles in Aerospace Engineering
Characterization Of Waviness In Wind Turbine Blades Using Air Coupled Ultrasonics, Sunil Kishore Chakrapani, Vinay Dayal, David K. Hsu, Daniel J. Barnard, Andrew Gross
Characterization Of Waviness In Wind Turbine Blades Using Air Coupled Ultrasonics, Sunil Kishore Chakrapani, Vinay Dayal, David K. Hsu, Daniel J. Barnard, Andrew Gross
Sunil Kishore Chakrapani
Waviness in glass fiber reinforced composite is of great interest in composite research, since it results in the loss of stiffness. Several NDE techniques have been used previously to detect waviness. This work is concerned with waves normal to the plies in a composite. Air‐coupled ultrasonics was used to detect waviness in thick composites used in the manufacturing of wind turbine blades. Composite samples with different wave aspect ratios were studied. Different wavy samples were characterized, and a three step process was developed to make sure the technique is field implementable. This gives us a better understanding of the effect …
Inspection And Evaluation Of Dry Fibers In Thick Composites, Vinay Dayal, Sunil Chakrapani, Daniel Barnard
Inspection And Evaluation Of Dry Fibers In Thick Composites, Vinay Dayal, Sunil Chakrapani, Daniel Barnard
Sunil Kishore Chakrapani
This paper presents the investigation of dry fibers in thick composites. Dry fibers can be defined as lack of epoxy in localized regions. These local regions act as potential defects in thick composites under compressive loads and act as an initiation point for defects such as matrix cracking and delamination. Detection and characterization of dryness in glass/epoxy composites, with thickness greater than one inch, is presented in this paper. One inch samples with dry fibers were fabricated and tested. Detection is carried out with the help of air coupled ultrasonics in both through transmission and singled sided inspection. To characterize …
Ultrasonic Testing Of Adhesive Bonds Of Thick Composites With Applications To Wind Turbine Blades, Sunil Kishore Chakrapani, Vinay Dayal, Ryan Krafka, Aaron Eldal
Ultrasonic Testing Of Adhesive Bonds Of Thick Composites With Applications To Wind Turbine Blades, Sunil Kishore Chakrapani, Vinay Dayal, Ryan Krafka, Aaron Eldal
Sunil Kishore Chakrapani
This paper discusses the use of pulse echo based ultrasonic testing for the inspection of adhesive bonds between very thick composite plates (thickness greater than 30 mm). Large wind turbine blades use very thick composite plates for its main structural members, and the inspection of adhesive bond-line is very vital. A wide gamut of samples was created by changing the thickness of plate and the adhesive. The influence of experimental parameters such as frequency on measurement is studied in this paper. Two different frequencies are chosen, and the measurement error bars are determined experimentally. T-Ray measurements were used to verify …
Investigation Of Ply Waviness In Wind Turbine Blades: Experimental And Numerical Analysis, Sunil Kishore Chakrapani
Investigation Of Ply Waviness In Wind Turbine Blades: Experimental And Numerical Analysis, Sunil Kishore Chakrapani
Sunil Kishore Chakrapani
Composite materials used in fabricating wind turbine blades use large tows, stitched fibers which are relatively thick compared to the composites used in many other applications. Thick fibers enables manufactures to save cost of the fiber and build up the thickness quickly, but introduces defects such as waviness, dry patch etc. Waviness in composites has been shown to degrade the tensile and compressive strength of the laminate. Waviness in a critical portion of the blade can lead to the catastrophic failure of the blade which is costly not only from the cost of the equipment but also the loss of …
Ultrasonic Rayleigh Wave Inspection Of Waviness In Wind Turbine Blades: Experimental And Finite Element Method, Sunil Kishore Chakrapani, Vinay Dayal, Daniel J. Barnard, Aaron Eldal, Ryan Krafka
Ultrasonic Rayleigh Wave Inspection Of Waviness In Wind Turbine Blades: Experimental And Finite Element Method, Sunil Kishore Chakrapani, Vinay Dayal, Daniel J. Barnard, Aaron Eldal, Ryan Krafka
Sunil Kishore Chakrapani
This paper presents the investigation of discrete, out-of-plane waviness in thick composite plates with applications to wind turbine blades. The investigation was carried out with the help of air coupled ultrasonics and a two-step procedure was framed to assist production line implementation. The first step involved detection of marcels, and the second step involved the characterization of these marcels with the help of an index called aspect ratio. A set of standardized samples with known aspect ratios were fabricated and used for this study. Finite element models were created to understand the wave propagation in wavy composite plates. All the …
Inspection Of Helicopter Rotor Blades With The Help Of Guided Waves And "Turning Modes": Experimental And Finite Element Analysis, Daniel J. Barnard, Sunil Kishore Chakrapani, Vinay Dayal
Inspection Of Helicopter Rotor Blades With The Help Of Guided Waves And "Turning Modes": Experimental And Finite Element Analysis, Daniel J. Barnard, Sunil Kishore Chakrapani, Vinay Dayal
Sunil Kishore Chakrapani
Modern helicopter rotor blades constructed of composite materials offer significant inspection challenges, particularly at inner structures, where geometry and differing material properties and anisotropy make placement of the probing energy difficult. This paper presents an application of Lamb waves to these structures, where mode conversion occurs at internal geometric discontinuities. These additional modes were found to successfully propagate to the targeted regions inside the rotor and back out, allowing evaluation of the structure. A finite element model was developed to simulate wave propagation and mode conversion in the structure and aid in identifying the signals received in the laboratory experiment. …
Investigation Of Waviness In Wind Turbine Blades: Structural Health Monitoring, Sunil Kishore Chakrapani, Vinay Dayal, Daniel J. Barnard
Investigation Of Waviness In Wind Turbine Blades: Structural Health Monitoring, Sunil Kishore Chakrapani, Vinay Dayal, Daniel J. Barnard
Sunil Kishore Chakrapani
Waviness in composite wind turbine blades was detected and characterized with the help of air coupled ultrasonics. Based on the aspect ratio, the detected marcels are either accepted or rejected. A passive structural health monitoring approach has been presented here to monitor the accepted marcels above a threshold. The fatigue life of specimen is most affected in the presence of a marcel. Hence this study focused on the damage evaluation after fatigue testing. Wavy laminate was subjected to fatigue load to investigate the fracture mechanisms near the marcel. Different types of defects were identified from this study and were used …