Composite laminate free-edge reinforcement with U-shaped caps. Part I - Stress analysis.

Howard, William; Gossard, Terry; Jones, Robert M.

doi:10.2514/3.10152

Cited by 21 publications

(8 citation statements)

References 8 publications

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“…Where b is the curved laminate width, y/b = 1 represents the free edge for the untreated laminate and the boundary between CFRP and resin edge for the treated laminate. The use of edge caps [2][3][4][5] has also been shown to reduce interlaminar direct stress but not interlaminar shear stress. The caps consist of a C-shape that is clamped around the laminate at the free edge.…”

Section: Figure 13mentioning

confidence: 99%

“…The high stress intensity caused by free edges has long been a known issue and there have been many techniques proposed to reduce it. Caps can be bonded onto the free edges and this has been shown to reduce interlaminar normal stress but does not significantly reduce interlaminar shear stress [2][3][4][5]. The edges can be altered to tailor structural properties, using an isotropic filler material and by changing the orientation of a ply near the free edge to reduce interlaminar stresses in this region [6].…”

Section: Introductionmentioning

confidence: 99%

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Resin treatment of free edges to aid certification of through thickness laminate strength

Fletcher

Kim

Dodwell

et al. 2016

Composite Structures

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Large aerospace parts are typically certified by testing narrow specimens, such as curved laminates, which have exposed free edges. These edges (not present in the production part) have been found to reduce the 3D strength of curved laminates by over 20%, showing this certification method is unreasonably conservative. The free edges also create a singularity, such that Finite Element (FE) modelling is challenging, which is typically approximated using non-linear analysis of cohesive interlaminar zones. A new treatment process is developed whereby a layer of resin is applied to the free edges of curved laminates. This significantly reduces the edge effect and delays failure. The resin edge treatment increases the strength of the curved laminate test specimens by 16%. The treatment also simplifies FE modelling by allowing for non-zero stresses normal to the laminate edge, removing the singularity. This enables use of linear FE models, which converge at the laminate edge. A linear FE method developed in this paper is conservative and predicts the strength of treated curved laminates to within 5% of the average test value. Hence it is shown that the resin edge treatment can be used to improve reliability of both certification tests and FE models.

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Section: Figure 13mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Resin treatment of free edges to aid certification of through thickness laminate strength

Fletcher

Kim

Dodwell

et al. 2016

Composite Structures

View full text Add to dashboard Cite

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“…Delamination is the main failure modes for composite laminates which can suffer up to 60% reduction in stiffness and still remain visibly unchanged [2]. Researchers proposed several solutions to solve or mitigate delamination-related problems [3][4][5][6][7][8][9]. Carbon nanofibers/nanotubes (CNFs/CNTs) proved to be the most effective solution in terms of mechanical reinforcement [10][11][12], but their difficult mixing process with the resin [13] and serious risks for human health [14] make them unsuitable in many cases.…”

Section: Introductionmentioning

confidence: 99%

Study on Mode I fatigue behaviour of Nylon 6,6 nanoreinforced CFRP laminates

Brugo

Minak

Zucchelli

et al. 2017

Composite Structures

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The benefits of interleaving polymeric electrospun nanofibers in between laminae of composite structure have been widely demonstrated in the past several years. Among the work that still has to be done, this paper aims to study delamination propagation of virgin and nanomodified specimens under Mode I fatigue loading. A 40-micron thick layer of Nylon 6,6 nanofibers have been produced and interleaved in carbon fiber-epoxy resin composite laminates; static and dynamic double cantilever tests have been performed to determine delamination growth onset and crack propagation rate vs. maximum energy release rate respectively. Nanomodified specimens exhibited improved delamination resistance during both the tests: delamination toughness increased 130% and cracks propagated 36 to 27 times slower than virgin interfaces. The benefits of the nanointerleave and its working mechanism have been explained using micrographs and SEM images, which revealed a double-stage reinforce mechanism

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“…External loads, impacts, fatigue, deformations, and so on may induce plies to debond and thus the so‐called delamination phenomena, which is the most common failure mode for composite laminates. Several methods have been developed over the years to enhance the delamination resistance of advanced composite laminates .…”

Section: Introductionmentioning

confidence: 99%

Influence of geometrical features of electrospun nylon 6,6 interleave on the CFRP laminates mechanical properties

2013

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Twenty plies, woven carbon fiber/epoxy matrix, virgin, and Nylon 6,6 electrospun nanofiber interleaved composite laminate beams are tested under Modes I and II fracture mechanic to assess the effect of nanointerleave on the global behavior of the laminate. Aim of the work is to study the effect of geometrical features of the nanoreinforce on the mechanical response of a laminate subjected to fracture mechanic loads. Nanofiber orientation, nanolayer thickness, and nanofiber diameter have been considered. From the experiments, mechanical parameters have been extracted and used to compare the configurations. The work highlights the importance of an accurate choice of the nanointerleave and showed that thick interleaves may weaken the interface if a high number of voids is left after the curing process, the smaller is the fiber diameter the higher is the energy absorbing capability of the specimens, and that fiber orientation has different effect depending on the loading mode

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Composite laminate free-edge reinforcement with U-shaped caps. Part I - Stress analysis.

Cited by 21 publications

References 8 publications

Resin treatment of free edges to aid certification of through thickness laminate strength

Resin treatment of free edges to aid certification of through thickness laminate strength

Study on Mode I fatigue behaviour of Nylon 6,6 nanoreinforced CFRP laminates

Influence of geometrical features of electrospun nylon 6,6 interleave on the CFRP laminates mechanical properties

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