Novel filler materials for composite out-of-plane joints

Sápi, Zsombor; Hutchins, Sam; Butler, Richard; Rhead, Andrew

doi:10.1016/j.compstruct.2019.111382

Cited by 10 publications

(7 citation statements)

References 22 publications

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“…When transverse bending loads are transmitted to the corner area of the T-joint, due to the significantly lower interlaminar mechanical properties of composite materials compared to that is inplane [7], the conventional T-joint may experience failure modes such as bonding interface failure, laminate delamination, and random crack propagation within the triangle filling area [8]. In order to improve the load-carrying capacity of the conventional T-joint, some researchers have adopted methods such as stitching [9][10][11][12], Z-pin [13][14][15], and triangle filling area reinforcement [1,16,17] to delay the failure in interlaminar and triangle filling areas. Moderate stitching and Z-pin can effectively delay and reduce delamination damage to the joint and improve its load-carrying capacity [18], but they may also weaken the in-plane mechanical properties of laminates [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…Moderate stitching and Z-pin can effectively delay and reduce delamination damage to the joint and improve its load-carrying capacity [18], but they may also weaken the in-plane mechanical properties of laminates [19][20][21]. Moreover, the filling material in the triangle area is still connected to the L-shaped layer through the resin matrix, and the triangle filling area remains a weak position for bearing load, thus the degree of improvement in the mechanical performance of joints by this method is limited [17]. It can be seen that conventional T-joints have always struggled to address the problem of interlaminar load transfer in the corner area, severely limiting the application potential of composite T-joints.…”

Section: Introductionmentioning

confidence: 99%

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A Novel Preparation Method of Composite Bolted T-joint with High Bending Performance Based on Prepreg-RTM Co-Curing Process

Zhang,

Luo,

Deng

et al. 2024

Preprint

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A co-curing resin system consisting of 9368 epoxy resin for prepreg and 6808 epoxy resin for resin transfer molding (RTM) was developed. A corresponding preparation method of novel polymer composite bolted T-joint with internal skeleton and external skin was proposed based on prepreg-RTM co-curing process, and novel T-joints were fabricated. A series of conventional configuration T-joints based on RTM process and T-joints made of 2A12 aluminum alloy were prepared simultaneously. Bending performances were studied on these T-joints experimentally. The results indicate that 9368 epoxy resin and 6808 epoxy resin exhibit good compatibility in rheological and thermophysical properties. The novel T-joints prepared with prepreg-RTM co-curing process show no obvious fiber local winding or resin-rich regions inside, and the interface quality between internal skeleton and external skin is excellent. The main failure modes of the novel T-joint under bending load include separation of skin and skeleton and fracture along the thickness on the base panel; the skeleton carries the main bending load, but there is still load transfer between external skin and internal skeleton through their interface. The internal damages of the novel T-joint are highly consistent with surface damages observed visually, facilitating the detection and timely discovery of damages. The initial stiffness, damage initiation load, and ultimate load of the novel T-joint are 1.65 times, 5.89 times, and 3.45 times that of conventional T-joint, respectively. When considering the influence of density, the relative initial stiffness and relative ultimate load of the novel T-joint are 1.44 times and 2.07 times that of aluminum alloy T-joint, respectively.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Novel Preparation Method of Composite Bolted T-joint with High Bending Performance Based on Prepreg-RTM Co-Curing Process

Zhang,

Luo,

Deng

et al. 2024

Preprint

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“…As illustrated in Figure 2, the polymer composite bolted T-joint with configuration (hereafter abbreviated as conventional T-joint) consists of two L ers, a bottom layer, a triangle filling area and outer wrapped skin, where L-s and base panel layers are composite laminates, and the triangle filling area m of resin matrix, short fibers, or twisted fibers [6]. When transverse bending lo mitted to the corner area of the T-joint, due to the significantly lower inte chanical properties of composite materials compared to that is in-plane [7] tional T-joint may experience failure modes such as bonding interface fail delamination, and random crack propagation within the triangle filling area to improve the load-carrying capacity of the conventional T-joint, some rese adopted methods such as stitching [9][10][11][12], Z-pin [13][14][15], and triangle filling a ment [1,16,17] to delay the failure in interlaminar and triangle filling are stitching and Z-pins can effectively delay and reduce delamination damag and improve its load-carrying capacity [18], but they may also weaken the chanical properties of laminates [19][20][21]. Moreover, the filling material in the is still connected to the L-shaped layer through the resin matrix, and the tr area remains a weak position for bearing load, thus the degree of improv mechanical performances of joints by this method is limited [17].…”

Section: Introductionmentioning

confidence: 99%

“…When transverse bending lo mitted to the corner area of the T-joint, due to the significantly lower inte chanical properties of composite materials compared to that is in-plane [7] tional T-joint may experience failure modes such as bonding interface fail delamination, and random crack propagation within the triangle filling area to improve the load-carrying capacity of the conventional T-joint, some rese adopted methods such as stitching [9][10][11][12], Z-pin [13][14][15], and triangle filling a ment [1,16,17] to delay the failure in interlaminar and triangle filling are stitching and Z-pins can effectively delay and reduce delamination damag and improve its load-carrying capacity [18], but they may also weaken the chanical properties of laminates [19][20][21]. Moreover, the filling material in the is still connected to the L-shaped layer through the resin matrix, and the tr area remains a weak position for bearing load, thus the degree of improv mechanical performances of joints by this method is limited [17]. It can be s ventional T-joints have always struggled to address the problem of inter transfer in the corner area, severely limiting the application potential of joints.…”

Section: Introductionmentioning

confidence: 99%

A Novel Preparation Method of Composite Bolted T-Joint with High Bending Performance Based on the Prepreg-RTM Co-Curing Process

Zhang,

Luo,

Deng

et al. 2024

Polymers

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A co-curing resin system consisting of 9368 epoxy resin for prepreg and 6808 epoxy resin for resin transfer molding (RTM) was developed. A corresponding preparation method for a novel polymer composite bolted T-joint with internal skeleton and external skin was proposed based on the prepreg-RTM co-curing process, and novel T-joints were fabricated. A series of conventional configuration T-joints based on the RTM process and T-joints made of 2A12 aluminum alloy were prepared simultaneously. Bending performances were studied on these T-joints experimentally. The results indicate that 9368 epoxy resin and 6808 epoxy resin exhibit good compatibility in rheological and thermophysical properties. The novel T-joints prepared with the prepreg-RTM co-curing process show no obvious fiber local winding or resin-rich regions inside, and the interface quality between the internal skeleton and the external skin is excellent. The main failure modes of the novel T-joint under bending load include the separation of the skin and skeleton and the fracture along the thickness on the base panel; the skeleton carries the main bending load, but there is still load transfer between external skin and internal skeleton through their interface. The internal damages of the novel T-joint are highly consistent with surface damages observed visually, facilitating the detection and timely discovery of damages. The initial stiffness, damage initiation load, and ultimate load of the novel T-joint are 1.65 times, 5.89 times, and 3.45 times that of the conventional T-joint, respectively. When considering the influence of the density, the relative initial stiffness and relative ultimate load of the novel T-joint are 1.44 times and 2.07 times that of the aluminum alloy T-joint, respectively.

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“…It was observed that the effects of the fillers on the initial failure load were little, whereas the normalized strength with integrally woven 3D inserts was enhanced by about 30% when compared the T-joints without the insert. Sápi et al 15 introduced eight novel filler concepts and experimentally validated against the baseline filler (noodle) via T-joint tensile tests. According to their study, the effects of the different fillers on the damage tolerance, the failure initiation load, strength were discovered.…”

Section: Introductionmentioning

confidence: 99%

Effects of the fillers on the interface strength of the hat-stiffened composite panel

Liu,

Guan

2023

Polymers and Polymer Composites

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Hat-stiffened composite skins have been widely used in primary structures of aircraft components. The bonding strength at the stiffener-skin interface is critical to ensure the advanced load-bearing capacity of the stiffened skin, whereas, the deltoid regions are usually the weakest locations because of the geometrical singularity. Inserting fillers into the deltoid regions could alter the bonding strength. In this study, a series of four-point bending tests are conducted on the co-cured hat-stiffened composite skin specimens with and without fillers and with different pre-fabricated debonding defects, furthermore, finite element simulations are implemented to predict the failure process. The stiffness, initial failure load, failure mode and failure process are analyzed to obtain the influences of the fillers on the damage tolerance of the hat-stiffened composite panels, and the influential mechanisms were revealed by the combined analyses of the test and simulation results. It is found that the usage of fillers can increase the initial stiffness of the panel without prefabricated defects by about 10%, but provide limited influence on the initial failure load. The pre-fabricated debonding defect along longitudinal direction has little influence on the stiffness and failure load, but the influence of the defect along transverse direction are higher. The initial failure of all hat-stiffened composite panels with/without filler and with/without prefabricated defects under four-point bending onsets around the deltoid region. The usage of the fillers changed the load transfer and the stress status in the deltoid region of the hat-stiffened composite panels and as a consequence, the initial failure modes were changed and the failure load were increased by the fillers. This work provides a technical support for the damage tolerance design and strengthening method of hat-stiffened composite structures.

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Novel filler materials for composite out-of-plane joints

Cited by 10 publications

References 22 publications

A Novel Preparation Method of Composite Bolted T-joint with High Bending Performance Based on Prepreg-RTM Co-Curing Process

A Novel Preparation Method of Composite Bolted T-joint with High Bending Performance Based on Prepreg-RTM Co-Curing Process

A Novel Preparation Method of Composite Bolted T-Joint with High Bending Performance Based on the Prepreg-RTM Co-Curing Process

Effects of the fillers on the interface strength of the hat-stiffened composite panel

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