Experimental evaluation of surface damage relaxation effect in carbon-fiber reinforced epoxy panels impacted into stringer

Дубинский, С. В.; Fedulov, Boris; Feygenbaum, Yuri; Gvozdev, Sergey; Metelkin, E. V.

doi:10.1016/j.compositesb.2019.107258

Cited by 10 publications

(7 citation statements)

References 14 publications

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“…The value of 0.24 mm is 17% smaller than the value measured directly after the impact. This observation is in accordance with the 20% of dent relaxation reported by Thomas [20] and the relaxation of 22% reported by Dubinskii et al [21]. Even though in both mentioned studies the relaxation was measured over a much longer time frame, in the present test series no further time-dependent relaxation was detected in measurements conducted after several days.…”

Section: Impact Testssupporting

confidence: 94%

“…Also, the dent depth reveals a significant scatter which even increases after the relaxation. This effect can also observed in the measured dent depth by Dubinskii et al [21]. The other characteristic values which derive from the force history curves, reveals only slight scattering.…”

Section: Impact Testssupporting

confidence: 76%

“…Even though in both mentioned studies the relaxation was measured over a much longer time frame, in the present test series no further time-dependent relaxation was detected in measurements conducted after several days. Possible influence factors on the time-dependent relaxation velocity might be the damage size, the material and the stacking sequence of the laminate which we can deduce from the different relaxation behavior in reported in the studies by Dubinskii et al [21] and Wagih et al [43].…”

Section: Impact Testsmentioning

confidence: 80%

“…The metric to assess the damage visibility in a damage tolerant design is the dent depth at the impact location. As shown by Thomas [20] or Dubinskii [21], significant relaxation of the dent depth after the impact has to be expected. The relevant dent depth to assess the visibility is the value after the relaxation, as stated in the Composite Materials Handbook [49].…”

Section: Damage Visibilitymentioning

confidence: 92%

“…This minimum is assumed as a linear function of the initial dent depth after the impact d ini . Further, Dubinskii et al [21] studied the dent relaxation in stiffened panels, considering the influence of time and the environmental conditions. In their experimental analysis, a relaxation between 22% and 61% was reported for the investigated conditions.…”

Section: Introductionmentioning

confidence: 99%

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An Experimental Study of the Cyclic Compression after Impact Behavior of CFRP Composites

Bogenfeld

Gorsky

2021

J. Compos. Sci.

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The behavior of impact damaged composite laminates under cyclic load is crucial to achieve a damage tolerant design of composite structures. A sufficient residual strength has to be ensured throughout the entire structural service life. In this study, a set of 27 impacted coupon specimens is subjected to quasi-static and cyclic compression load. After long intervals without detectable damage growth, the specimens fail through the sudden lateral propagation of delamination and fiber kink bands within few load cycles. Ultrasonic inspections were used to reveal the damage size after certain cycle intervals. Through continuous dent depth measurements during the cyclic tests, the evolution of the dent visibility was monitored. These measurements revealed a relaxation of the indentation of up to 90% before ultimate failure occurs. Due to the distinct relaxation and the short growth interval before ultimate failure, this study confirms the no-growth design approach as the preferred method to account for the damage tolerance of stiffened, compression-loaded composite laminates.

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Section: Impact Testssupporting

confidence: 94%

Section: Impact Testssupporting

confidence: 76%

Section: Impact Testsmentioning

confidence: 80%

Section: Damage Visibilitymentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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An Experimental Study of the Cyclic Compression after Impact Behavior of CFRP Composites

Bogenfeld

Gorsky

2021

J. Compos. Sci.

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Experimental investigations into damage mechanism in the low‐velocity impact and tension‐after‐impact testing of z‐pin reinforced curved CFRP composite

Liu,

Sang,

Jin

et al. 2024

Polymer Composites

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This paper studies the influence of z‐pins on the impact resistance and residual tensile properties of composite large curvature components through low‐velocity impact and tension‐after‐impact tests to explore the damage mechanism. Unpinned and z‐pinned specimens with different diameters (0.3 and 0.5 mm) and spacing (3, 4, and 5 mm) were impacted at energies of 28 J and 14 J + 14 J and were stretched until failure. The theoretical models were used to predict impact dent depth and tensile strength, and the effectiveness of z‐pins and damage patterns were characterized by force‐time/displacement curves and through visual observation. The agreement between the experiments and predictions can thus validate the presented approach. Through the low‐velocity impact test, it is found that z‐pins with higher density and smaller diameter make the impact dent shallower and the surface damage less, thus showing better performance. Later, the impacted specimens mainly show delamination, explosion, breakage, and splitting after tension. During the first stage of the force‐displacement curves, since z‐pins mitigate the delamination, tensile strength shows a 29.58%–59.17% increase while in the third stage, a decrease of 3.95%–15.12% occurs due to initial damage caused by z‐pins.Highlights Different impact energies are implemented on large curved CFRP laminates of z‐pins with different diameters and spacing to explore the damage mechanism. Low‐velocity impact and tension‐after‐impact (TAI) tests are used to simulate the centrifugal force of the blade subjected to impact and rotation after impact. Z‐pinned group with a small diameter and high density causes less damage and tensile strength in the first stage increases while decreasing in the third stage compared with the unpinned group.

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A method of predicting visual detectability of low-velocity impact damage in composite structures based on logistic regression model

Jiang

Guan

et al. 2021

Chinese Journal of Aeronautics

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Experimental evaluation of surface damage relaxation effect in carbon-fiber reinforced epoxy panels impacted into stringer

Cited by 10 publications

References 14 publications

An Experimental Study of the Cyclic Compression after Impact Behavior of CFRP Composites

An Experimental Study of the Cyclic Compression after Impact Behavior of CFRP Composites

Experimental investigations into damage mechanism in the low‐velocity impact and tension‐after‐impact testing of z‐pin reinforced curved CFRP composite

A method of predicting visual detectability of low-velocity impact damage in composite structures based on logistic regression model

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