Towards a practical structural health monitoring technology for patched cracks in aircraft structure

Baker, A.A.; Rajic, Nik; Davis, Claire

doi:10.1016/j.compositesa.2008.09.015

Cited by 82 publications

(46 citation statements)

References 2 publications

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“…Experimental studies showed variation in the nonlinear response of the joints due to the applied loadings. Baker et al (2009) demonstrated the effectiveness of the strain-based SHM approach for monitoring the boron-epoxy patch repair of a critical fatigue crack in F-111C wing. In addition, conventional strain gages were used in the SHM system.…”

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confidence: 99%

Experimental analyses of metal-composite bonded joints: damage identification

2014

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The advent of composite co-cured and co-bonded integrated construction in aircraft structures has lead to the replacement of fastened joints with bonded joints between the skins and the stiffeners. Skin-stiffener debondings could occur due to impact or other operational reasons and it is usually internal failure. Damage identification of bonded components, which are often vital elements in many structures, is crucial for the prevention of failure of the entire structure. Thus, different researchers have investigated vibration-based methods as an alternative technique to be used in the structural health monitoring (SHM) systems. Hence, this work consists of investigating experimentally through the vibration-based method, the dynamic behavior changes in a bonded metal-composite structure by using piezoelectric transducer and accelerometers in order to monitory the damage. The damage is an artificial debonding in the joint, which was simulated by inserting Teflon™ tapes within the joint. In-situ inspection as ensured by accelerometer and piezoelectric transducers (PZT) bonded to the structure. Indeed, with a simple comparison of the frequency response functions is difficult to conclude if there is damage in the structure, unless a large damage is presented. However, by using damage metrics, it is possible to identify the damage with more accuracy. Thus, the experimental results obtained by the accelerometers were compared to the data provided by the smart composite sensors (PZT). Finally, it was discussed the advantages and limitations of the experimental analyses and the identification technique proposal.

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confidence: 99%

Experimental analyses of metal-composite bonded joints: damage identification

2014

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“…The effectiveness of sensor bonding with its host structure was estimated by Giurgiutiu, 2008 andBaker et al, 2008. The deboning and crack defects of the piezoelectric elements were identified under varying structural load conditions; the change in capacitive values of the piezoelectric materials during the de-bonding of the sensors with their host structures was estimated earlier by Park et al, 2006;Sohn and Lee, 2009.…”

Section: Review Of Shmmentioning

confidence: 99%

“…These approaches use the Bragg grating optical fibers as strain gauges and helps in patch repair. Rodrigo et al (2009) demonstrated how the strain based methodology can be utilized to detect the crack propagation in secondary bonded woven E-glass/vinyl ester composite double plate joints (Baker et al, 2008).…”

Section: Review Of Shmmentioning

confidence: 99%

Inspection of Parts with Complex Geometry and Welds with Structural Health Monitoring Techniques

Korla¹

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“…However a problem with bonded repairs is the difficulty in assessing their strength ( (Noor, 2000), p134). "In response to concerns with the inability to predict the long term integrity of adhesive bonds, severe limitations are imposed on the certification of bonded composite repairs to flight safety structure" ( (Baker et al, 2009. This requirement limits the application of composite bonded patches "to non-primary structures due to the lack of methodology for monitoring the damaged state of the repaired structure" ( (Chapuis et al, 2008), p666).…”

Section: Bonded Patch Repairsmentioning

confidence: 99%

“…These "can only be applied at prescribed intervals when the aircraft is scheduled for servicing" ( (Baker et al, 2009. "SHM offers an alternative approach in which the health or integrity of the patch system is autonomously monitored, possibly on a continuous basis" ( (Baker et al, 2009.…”

Section: Bonded Patch Repairsmentioning

confidence: 99%

Investigation of the effects of structure-sensor interaction on piezoceramic transducers for structural health monitoring applications

Favier¹

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Surface bonded piezoceramic transducers used for structural health monitoring that are subjected to high strain loading are at risk of being compromised by damage to the attaching bond line or to the piezoceramic sensing element. In consequence, when baseline sensor data for a healthy structure is compared to subsequent data obtained from damaged sensors, incorrect assessment of the state of the structure may occur.This project investigated and developed a novel method of attaching piezoceramic transducers to specially prepared thermoset composite surfaces using functional thermoplastic surfaces as bond line media with the aim to improve the protection of the transducer from the damaging effects of high strain structural loading.To evaluate the effectiveness of this new approach, the fatigue performance of thermoplastic weld bonded and cyanoacrylate adhesive bonded transducers were compared.Finite element analysis (FEA) of transducer-bondline-structure models showed that strain transfer from the structure to the piezoceramic element reduced as bond layer thickness increased or as the bond layer modulus decreased. The simulations indicated that within each material layer shear strain changes gradually and the rate of change is different for each material type. At dissimilar material interface boundaries shear strain has a common value but the change gradient differences within each material mean the interface is a likely location for transducer failure.For cyanoacrylate and thermoplastic bonding systems the availability of published data regarding bond strength is limited. Static tensile testing was undertaken to generate some of the bond strength data for different bond layer thicknesses and a range of surface roughness. The data showed that tensile bond strength increased with decreasing adhesive layer thickness and that for the range of surface roughness tested the relative performance of each bond line thickness was similar.To further examine the performance of the two different bonding systems, fatigue testing was undertaken. The relative performance of each system was compared using transducer output voltage and impedance data. Specimens were fabricated by bonding 10 mm diameter, 1 mm thick silver electroded piezoceramic transducers to appropriately ii prepared thermoset composite test coupons. Test samples were subjected to sinusoidal loading at 5 Hz and maximum strains of 1000 µɛ, and 2000 µɛ or 3000 µɛ.For both bond types, sensor voltage output showed an initial period of rapid decrease in amplitude before typically settling at an approximate steady state output. The lower voltage output from the thermoplastic bonded transducers indicated that the thermoplastic bond lines reduced strain transfer between the host structure and the piezoceramic sensing element.The fatigue test results showed that polyvinylidene fluoride (PVDF) bonded transducers experienced a reduced or similar decrease in performance relative to the cyanoacrylate bonded transducers for the same number of load cycles and strain ran...

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Towards a practical structural health monitoring technology for patched cracks in aircraft structure

Cited by 82 publications

References 2 publications

Experimental analyses of metal-composite bonded joints: damage identification

Experimental analyses of metal-composite bonded joints: damage identification

Inspection of Parts with Complex Geometry and Welds with Structural Health Monitoring Techniques

Investigation of the effects of structure-sensor interaction on piezoceramic transducers for structural health monitoring applications

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