Performance of Patch Repaired Composite Panels - Static and Fatigue

Darwish, Feras H.; Shivakumar, Kunigal; Hamoush, Sameer; Hsu, David K.

doi:10.2514/6.2006-2271

Cited by 5 publications

(4 citation statements)

References 6 publications

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“…This clearly indicates the importance of good bonding adhesion and the bonding geometry between the filler plies and the parent material. Additional test data also indicate that a bond line angle of less than 60° with respect to the load direction would restore the strength nearly to that of an undamaged composite strength [73]. This adds to the validity to the importance of the bonding geometry.…”

Section: Scarf Repairmentioning

confidence: 75%

“…Repairs are essential for performing life extensions of structures that may have reached their service life or may have been damaged prematurely. Bonded composite patch repair methodologies are seen as the most viable method for repair because the fiber reinforced layers of the repair patch can be optimized to handle any magnitude and direction of loads that are seen during service [73].…”

Section: Repairmentioning

confidence: 99%

“…Scarf repairs has been shown to have several advantages over other repair methods, including [73,81,[83][84]: (1) scarf-repair in moisture conditioned state show an increase in the shear strength as the testing temperature decreases, (2) scarf repairs do not add high amounts of resin meaning it does not modify the percentage relation between fiber and matrix, (3) scarf joints experience lower peel stress compared to other joint configurations, (5) existence of a small delamination under the surface layer of the patch does not affect the performance of scarf-repaired panel under static tensile load, ( 6) the repairs are only marginally thicker than the parent material, ( 7) each repair ply overlaps the ply that it is repairing resulting in a straighter and stronger load path, ( 8) scarf repairs minimize the secondary effects of bending and, ( 9) scarf repairs offer a flush finish and have the ability to repair thick structures. The disadvantages of scarf repair are as follows [79,[83][84]: (1) scarf repairs are more difficult to apply, (2) scarf repair techniques induces small resin-rich regions in the laminate which can contribute to strength reduction of the composite, (3) scarf repairs are very time consuming, and ( 4) resin heterogeneity and the discontinuity of the reinforcement in the repaired areas leads to differences in strength and fatigue resistance of original and scarf-repaired composites.…”

Section: Scarf Repairmentioning

confidence: 99%

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Numerical modelling of impact damage on carbon fiber reinforced polymer laminates

Roy¹

2021

Preprint

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In recent years, the usage of carbon fiber reinforced polymers in the aviation industry has increased significantly. While numerous advancements have been made in the field of testing and analysis of advanced composites, improvements can still be made in terms of time and cost. This thesis is focused on numerical modelling of nonlinear three-dimensional transient-dynamic impact damage, and also assesses various numerical techniques for reducing computational costs while maintaining the accuracy of results under impact loadings. This thesis does so using three studies and the computational package LS-DYNA. The first study is performed to elucidate the behaviour of a stiffened thin-walled fuselage section subjected to low-velocity, high-energy blunt impact. The fuselage section is comprised of thin skin panels, stringers, frames and shear ties, all of which are modelled as multidirectional carbon fiber laminates. The critical locations during the impact, the failure sequence, and the failure loads, locations and times are all identified. The obtained numerical results are compared to experimental results on low-velocity impacts on composite

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Section: Scarf Repairmentioning

confidence: 75%

Section: Repairmentioning

confidence: 99%

Section: Scarf Repairmentioning

confidence: 99%

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Numerical modelling of impact damage on carbon fiber reinforced polymer laminates

Roy¹

2021

Preprint

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“…According to the research of Darwish et al, 20 the use of a circular bonded scarf patch repair for a composite panel under static tensile test can restore up to 93% of its tensile strength, especially when used on critical, highly loaded components. Because the flush scarf patch repair eliminates load eccentricity, which causes peel stresses in lap joints, and is more aerodynamically appropriate, it has become a preferred repair method, especially for thick, solid composite laminates.…”

Section: Introductionmentioning

confidence: 99%

Stress model and strain energy release rate of a prescribed crack in scarf joint/repair of composite panels

Yang

Tomblin

Salah

2015

Journal of Composite Materials

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An analytical model for stress distribution was derived and an analytical model for determining the strain energy release rate of a prescribed crack in a scarf joint or a bonded scarf repair of a composite panel was developed. The crack closure method was used to calculate the strain energy release rate at the crack tip after a prescribed crack was inserted at high adhesive stress locations. In the stress model, the first-order laminated plate theory was applied to the composite panels, including the following: (1) scarfed parent substrate and corresponding repair panel for a bonded scarf repair or (2) both adherend panels for a scarf joint, assuming a linear elastic adhesive. The bondline was presumed to be thin, so the adhesive stresses were presumed to be uniform through the thickness. The coupled second-order differential equations obtained via kinematics and force equilibrium were solved semi-numerically using the symbolic computational tool Maple. Finite element analyses using the commercial software ABAQUS™ were conducted for comparison purposes, and results correlated well with the developed analytical model. Experimental strain data of the bonded scarf repairs was also used to verify the developed model. It can be seen that the highest adhesive stresses occur at locations where high-stiffness plies are discontinued. The obtained strain energy release rate can be used for failure analysis if appropriate critical energy release rates in conjunction with proper mode mixture rule are used.

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