Strength of scarf-bonded CFRP repairs containing disc-shaped zones of weak bonding considering hot-wet conditioning

Harder, Sergej; Röper, Florian; Gibhardt, Dennis; Koert, Benedikt; Fiedler, Bodo

doi:10.1016/j.ijadhadh.2020.102643

Cited by 6 publications

(4 citation statements)

References 20 publications

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“…The repair site of the FRP component prepared in this way is then mostly filled up with preimpregnated layers, so-called prepregs [6][7][8][9]. There are several approaches to repair FRP structures, e.g., the scarf method or doubler method [6,[10][11][12][13][14][15][16]. These initial repair processes are always associated with high manual effort and manufacturing expenses and often significantly reduce the composite strength of the repaired component or cause extra weight.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Bonding Mechanism between Overlapping Textile Layers for FRP Repair Based on Dry Textile Patches

Rabe,

Arbulu,

Häntzsche

et al. 2023

Materials

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Lots of damaged fiber-reinforced plastic (FRP) components are replaced by new components instead of repairing. Furthermore, only very labor-intensive repair methods are available on the market to fully restore the integrity of the structure. This requires a high level of experience or, alternatively, very cost-intensive technology, such as the use of computer tomography and robotics. The high costs and CO2 emissions caused by the manufacture of FRP components then bear no relation to their service life. The research project IGF-21985 BR “FRP-Repair” aims to solve the named challenges. Using semiconductor oxide catalysts, the matrix can be locally depolymerized by ultraviolet (UV) radiation, and thus removed from the damaged area of the FRP component. Subsequently, the damaged fibers in this area can be detached. By using customized textile repair patches and local thermoset reinfiltration, the repair area is restored. With this process, the fiber structure can be repaired locally with new fibers on the textile level. The repair is similar to the original production of a fiber composite in an infusion process. No additional adhesive material is used. As a result, repaired FRP structures with restored mechanics and a near-original surface can be realized. This article provides an insight into the actual steps of the development of the FRP component repair process using dry textile patches. The empirical investigation of overlapped rovings and UD material showed the expected results. Residual fracture forces of up to 86% could be achieved. The most interesting approach on the roving level was splicing the overlapping fibers. The free ends of the fibers of the patch and part are mechanically bonded. This bond at the textile level is further strengthened by infusion with matrix.

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Section: Introductionmentioning

confidence: 99%

Investigation of the Bonding Mechanism between Overlapping Textile Layers for FRP Repair Based on Dry Textile Patches

Rabe,

Arbulu,

Häntzsche

et al. 2023

Materials

View full text Add to dashboard Cite

show abstract

“…The repair site of the CFRP component prepared in this way is then mostly filled up with pre-impregnated layers, so-called prepregs [ 7 , 8 , 9 , 10 ]. There are several approaches to repair CFRP structures, e.g., the scarf method or doubler method [ 7 , 11 , 12 , 13 ]. These initial repair processes are always associated with high manual effort and manufacturing expenses and often significantly reduce the composite strength of the repaired component or cause extra weight.…”

Section: Introductionmentioning

confidence: 99%

Novel Repair Procedure for CFRP Components Instead of EOL

Rabe¹,

Böhnke²,

Kruppke³

et al. 2021

Materials

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Today, numerous carbon fiber (CF) reinforced plastic (CFRP) components are in continuous usage under harsh environmental conditions. New components often replace damaged structural parts in safety-critical applications. In addition to this, there is also no effective repair method to initially restore the mechanics of these structures using dry fiber material. The high costs of CFRP components are not in proportion to their lifetime. The research project IGF-19946 BR “CFRP-Repair” addresses this specific challenge. By using an oxide semiconductor that is activated by ultraviolet (UV) irradiation, the thermoset matrix can be depolymerized and thus locally removed from the damaged CFRP component. Afterward, the harmed fibers can be physically removed from the laminate in this certain area. A load-adjusted tailored fiber reinforcement patch is subsequently applied and consolidated by local thermoset re-infiltrating. Using this procedure, the structure can be locally repaired with new CF. As a result, repaired CFRP structures can be obtained with reduced mechanics and an approximately original surface. This article gives an insight into the developed repair procedure of CFRP components in an innovative and more efficient way than the state-of-the-art.

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“…However, achieving its full recovery potential depends directly on the quality of the bondline which is difficult to keep consistence, because it has to be carried out in a controlled environment and depends on the skills of the technician [1]. Hence, the repair quality can vary significantly and currently there is no consistent way of evaluating the strength of a bondline without destructive testing [2,3]. Therefore, the need for developing techniques which could monitor and assess the bondline strength during manufacture and in service is an important area of research.…”

Section: Introductionmentioning

confidence: 99%

Damage detection & localization on composite patch repair under different environmental effects

Lambinet

Khodaei

2020

Eng. Res. Express

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This paper presents a structural health monitoring (SHM) methodology for detecting damage in a composite bonded repair. The application of guided wave based techniques in a step-sanded bonded repair under operational and environmental load is thoroughly investigated. A two step damage detection and localization algorithm is presented, were in the first level the path damage indices (PDIs) for each transducer pair is calculated. The PDIs are then compared to a set threshold (based on the environmental and operational conditions) to increase the reliability of damage detection while reducing false alarm. In addition, a self-diagnosis approach based on electro-mechanical impedance (EMI) measure is proposed to identify the faulty sensors prior to the diagnosis. Once the transducer pairs with possible damage in their path has been selected, the second level of the proposed methodology is damage localization. To address the challenge of edge reflection, complex geometrical shape and layup of the repair patch which introduced anisotropy to the wave propagation, a novel damage detection based on probability imaging technique is proposed. The methodology is developed based on assigning probabilities of damage to the Minimal Intersection Score (MIS) to reduce the path saturation related to each path having the same probability of damage being located anywhere along it. The proposed method, uses a smart sub-division technique based on Voronoi Tessellation which is adaptable to any shape (circular, rectangular, elliptical). The reliability of the proposed method is then demonstrated with experimental results on a composite step-sanded repair subjected to impact damage under vibration and temperature variations, and the choice of input parameters such as wave form and excitation frequency on the probability of detecting damage is demonstrated.

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Strength of scarf-bonded CFRP repairs containing disc-shaped zones of weak bonding considering hot-wet conditioning

Cited by 6 publications

References 20 publications

Investigation of the Bonding Mechanism between Overlapping Textile Layers for FRP Repair Based on Dry Textile Patches

Investigation of the Bonding Mechanism between Overlapping Textile Layers for FRP Repair Based on Dry Textile Patches

Novel Repair Procedure for CFRP Components Instead of EOL

Damage detection & localization on composite patch repair under different environmental effects

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