Smart cure cycles for fiber metal laminates using embedded fiber Bragg grating sensors

Prussak, Robert; Stefaniak, Daniel; Kappel, Erik; Hühne, Christian; Sinapius, Michael

doi:10.1016/j.compstruct.2019.01.079

Cited by 33 publications

(27 citation statements)

References 26 publications

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“…The tensile strength is between 500 and 700 MPa, with a yield strength of 210 MPa and a Young's modulus of 200 GPa. Due to its good mechanical and durability properties, the alloy is used in aircraft construction and automotive engineering, and has been used in multiple previous studies on fibre metal laminates [8,[23][24][25][26][27].…”

Section: Materials and Specimen Preparationmentioning

confidence: 99%

CFRP Thin-Ply Fibre Metal Laminates: Influences of Ply Thickness and Metal Layers on Open Hole Tension and Compression Properties

et al. 2020

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Thin-ply laminates exhibit a higher degree of freedom in design and altered failure behaviour, and therefore, an increased strength for unnotched laminates in comparison to thick-ply laminates. For notched laminates, the static strength is strongly decreased; this is caused by a lack of stress relaxation through damage, which leads to a higher stress concentration and premature, brittle failure. To overcome this behaviour and to use the advantage of thin-ply laminates in areas with high stress concentrations, we have investigated thin-ply hybrid laminates with different metal volume fractions. Open hole tensile (OHT) and open hole compression (OHC) tests were performed with quasi-isotropic carbon fibre reinforced plastic (CFRP) specimens. In the area of stress concentration, 90° layers were locally substituted by stainless steel layers of differing volume fractions, from 12.5% to 25%. The strain field on the specimen surface was evaluated in-situ using a digital image correlation (DIC) system. The embedding of stainless steel foils in thin-ply samples increases the OHT strength up to 60.44% compared to unmodified thin-ply laminates. The density specific OHT strength is increased by 33%. Thick-ply specimens achieve an OHC strength increase up to 45.7%, which corresponds to an increase in density specific strength of 32.4%.

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Section: Materials and Specimen Preparationmentioning

confidence: 99%

CFRP Thin-Ply Fibre Metal Laminates: Influences of Ply Thickness and Metal Layers on Open Hole Tension and Compression Properties

et al. 2020

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“…In the infusion process, integrated sensors can not only be used to determine the degree of cure, because a sufficiently dense network additionally allows the detection of the flow front [1] in advance of the curing reaction. A comparatively new topic is represented by so-called smart cure cycles [2,3], in which residual stress states are to be reduced by lowering the temperature of the curing component when the gel point is reached. In this way, a stress-free temperature closer to the actual service temperature of the component is achieved and residual stresses decrease while the load-bearing capacity of the component is increased.…”

Section: Introductionmentioning

confidence: 99%

“…In this way, a stress-free temperature closer to the actual service temperature of the component is achieved and residual stresses decrease while the load-bearing capacity of the component is increased. While Kim et al still predicted the gel point using simulations based on DSC data [3], Prussak et al instead used integrated fibre Bragg sensors [2], which determine the point at which a mechanical interaction between the epoxy resin and the surrounding laminate begins.…”

Section: Introductionmentioning

confidence: 99%

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Reducing the Weakening Effect in Fibre-Reinforced Polymers Caused by Integrated Film Sensors

et al. 2021

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Integrating foil sensors into fibre-reinforced plastics offers the advantage of making manufacturing measurable with spatial resolution and thus simplifies quality control. One challenge here is the possible negative influence of the integrated sensors on the mechanical behaviour of the structure. This article shows how the different parts of a film sensor influence important mechanical strength parameters of fibre composites. A comparison of two thermoplastic carrier films shows that by choosing polyetherimide (PEI) instead of polyimide (PI), a considerably more advantageous failure behaviour of the composite is achieved. While integrated PI films reduce the interlaminar shear strength by 68%, no impairment is noticeable due to PEI films. For the critical energy release rate, PEI-based film sensors even lead to a significant increase, while a significant deterioration of 85% can be observed for PI-based sensors. However, not only the film substrate plays a decisive role for the interlaminar shear strength, but also the sensor structures themselves. In this article, sensor structures made of gold were investigated. The decisive parameter for the impairment seems to be the area share of gold structures in the sensor. For a sensor pattern made of gold lines with an area filling of 50%, a reduction of the interlaminar shear strength of up to 25% was observed depending on the angle between the shear stress and the gold lines. No impairment was observed for sensor structures with less gold area. The results show that PEI substrates can be a superior alternative for sensor integration into fibre composites and suggest that there is a trade-off between sensitivity and degradation of mechanical properties when designing interdigital sensors.

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“…Furthermore, they can initiate cracks in the fiber-matrix interface which can result in delamination and premature component failure [2]. The stresses depend on the process history and can be influenced by the curing process itself [5,6]. In the initial state, the matrix usually behaves like a liquid.…”

Section: Introductionmentioning

confidence: 99%

Phenomenological Analysis of Thermo-Mechanical-Chemical Properties of GFRP during Curing by Means of Sensor Supported Process Simulation

2020

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Inherent process-induced deformations (PID) and residual stresses impede the application of composite parts. PID lead to a geometrical mismatch in assemblies and require subsequent work for tolerance compensation. Unknown residual stresses cause overweighted structures resulting from unnecessary high safety factors. To counteract the deformations, the tool design needs to be modified until the component geometry meets the specifications. This process is mostly carried out empirically and is time and cost intensive. To improve the efficiency of the development process, an in-deep comprehension of the manufacturing processes is mandatory. Therefore, experimental and simulation-based methods are increasingly applied and enhanced. The object of this work is to investigate the development of process-induced strains as well as the material behaviour during the manufacturing for a GFRP plate. The process-induced strains are monitored by optical fiber Bragg grating (FBG) sensors. The change of the material phases is detected by dielectric sensors. Furthermore, a detailed process simulation considering viscoelastic effects and reaction kinetics is performed. Finally, the measurements are correlated with the simulation data to validate the simulation approach. A very good correlation for both the reaction kinetics as well as the process-induced strains is observed.

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Smart cure cycles for fiber metal laminates using embedded fiber Bragg grating sensors

Cited by 33 publications

References 26 publications

CFRP Thin-Ply Fibre Metal Laminates: Influences of Ply Thickness and Metal Layers on Open Hole Tension and Compression Properties

CFRP Thin-Ply Fibre Metal Laminates: Influences of Ply Thickness and Metal Layers on Open Hole Tension and Compression Properties

Reducing the Weakening Effect in Fibre-Reinforced Polymers Caused by Integrated Film Sensors

Phenomenological Analysis of Thermo-Mechanical-Chemical Properties of GFRP during Curing by Means of Sensor Supported Process Simulation

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