Fractography and failure mechanisms in static mode I and mode II delamination testing of unidirectional carbon reinforced composites

Bonhomme, J.; Argüelles, A.; Viña, J.; Viña, I.

doi:10.1016/j.polymertesting.2009.05.003

Cited by 76 publications

(38 citation statements)

References 14 publications

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“…These aspects originate from several microcracks that coalesce ahead of the crack tip as Mode II crack growth arises. These microcracks are oriented at 45° due to the shear stress resultant from this mode and the fracture surface area generated in this process is responsible for the higher values of G IIC . As the adherents move in opposite directions relative to each other due the shear loading applied under Mode II, top and bottom fracture surfaces will present cusps that tilt to directions that oppose to each other .…”

Section: Resultsmentioning

confidence: 99%

Hygrothermal effects on mode II interlaminar fracture toughness of co‐bonded and secondary bonded composites joints

et al. 2018

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Adhesive joints are being more extensively applied in the aeronautical industry, allowing for better integration between the structural parts and overall lower weight if compared with joints made with fasteners and rivets. However, a further evaluation of these new technologies is needed, once their critical fracture toughness under different environmental conditions is still unknown and this value is essential for design and certification of aircraft manufactured with these materials. Thus, this work focuses on the mode II fracture toughness characterization of carbon fiber composite laminates joined by co‐bonded (CB) and secondarily bonded (SB) techniques, using EA 9695 epoxy adhesive aged at different environmental conditions (room temperature ambient—RTA and elevated temperature wet—ETW). Dynamic mechanical analysis (DMA) was used to understand the effect of moisture absorption on the glass transition of materials and on the decreasing of Mode II fracture toughness after aging. The DMA results showed a reduction of 11% in Tg values for the GIIc values of ETW samples in comparison with specimens tested at RTA condition. Reductions about 92 and 94% in Mode II fracture toughnesses were obtained for CB and SB aged specimens, respectively when compared with the toughness values obtained for specimens tested at RTA. Further inspection of the fracture surfaces using scanning electron microscope proved that light fiber‐tear fracture occurred at both RTA and ETW conditions for CB joints, while fracture was mainly light‐fiber‐tear at RTA condition, becoming mostly cohesive after aging for SB joints. POLYM. COMPOS., 40:3220–3232, 2019. © 2018 Society of Plastics Engineers

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Section: Resultsmentioning

confidence: 99%

Hygrothermal effects on mode II interlaminar fracture toughness of co‐bonded and secondary bonded composites joints

et al. 2018

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“…Como determinado por muitos pesquisadores, a morfologia predominante nas faces da fratura, resultantes de carregamento em Modo II, são as formações denominadas de "cusps" no Reino Unido [13][14][15][16] ou "hackles" nos Estados Unidos da América [3,4,17,18] . Neste trabalho, é adotada a nomenclatura de cúspides para identificar esse aspecto comum da fratura interlaminar.…”

Section: Cândido G M Et Al -Fractografia De Compósito Estrutural unclassified

Fractografia de Compósito Estrutural Aeronáutico Submetido ao Ensaio de Tenacidade à Fratura Interlaminar em Modo II

Cândido¹,

Rezende²,

Donadon³

et al. 2014

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Resumo: A fractografia consiste no estudo detalhado da morfologia da superfície de fratura de materiais. Para isto, a técnica de microscopia eletrônica de varredura (MEV) é usualmente utilizada para determinar a causa de falha e a relação do modo de falha com a microestrutura do material em análise. Essas informações permitem estabelecer analogia entre estrutura, propriedade e processamento do material com a iniciação e a propagação da falha. Neste estudo, a análise fractográfica é utilizada para investigar os aspectos que caracterizaram a falha por delaminação em Modo II de laminados poliméricos de uso estrutural. Para isto, espécimes com um inserto de Teflon  introduzido no plano médio de uma das extremidades do laminado (End-Notched) foram submetidos ao ensaio de carregamento em flexão em quatro pontos. Os espécimes foram preparados a partir de um laminado fabricado em autoclave, com camadas (0°, 90°) de material pré-impregnado de tecido bidirecional em estilo plain weave de fibras de carbono IM7/ resina epóxi M21. Os resultados da análise mostram que a superfície de fratura é muito irregular, com a visualização de fibras e impressões de fibras na matriz. Aspectos fractográficos de cúspides e formatos de concha, originados durante o cisalhamento da matriz polimérica, são também observados. Palavras-chave: Fractografia, laminado compósito, delaminação em Modo II. Fractography of Aeronautical Structural Composite Submitted to Mode II Interlaminar Fracture Toughness TestAbstract: Fractography involves a detailed study of the fractured surface morphology of materials. Usually the Scanning Electron Microscopy (SEM) technique is applied to investigate the cause of failure and the relationship between failure modes and the microstructure of the material under investigation. This information allows one to relate structure, processing methods and materials properties with the onset in their failure and propagation. In this study, fractographical analysis is employed to investigate the failure aspects induced by Mode II delamination of structural fiber-reinforced polymer composite laminates. Samples with Teflon  inserted at the mid-plane of one end of the laminate (end-notched specimens) were subjected to four-point bending (4-ENF) test. The samples were prepared from laminates manufactured in autoclave with prepreg layers (0°, 90°) of IM7 plain weave woven fabric fiber architecture and M21-epoxy resin. The results indicate that the fracture surface is very irregular where fibers and fiber prints at the matrix are visualized, along with fractographic aspects named cusps and scallops, formed during the polymeric matrix shearing.

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“…Fractography Analysis SEM fractography analysis was performed on samples of both materials extracted from the insert edge and crack growth zone of the specimens tested under mode I static and fatigue loading [27,28]. Figure 9 (a) and (b) represent 100× magnification micrographs of the near crack front fracture surfaces of specimens tested under static mode I loading for the materials AS4/8552 and AS4/3501-6, respectively.…”

Section: Delamination Crack Growthmentioning

confidence: 99%

Influence of the Matrix Type on the Mode I Fracture of Carbon-Epoxy Composites Under Dynamic Delamination

et al. 2010

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The delamination energy and fracture behaviour under static and dynamic mode I loading of two composites, made of the same unidirectional carbon reinforcement embedded in two different matrices, one tough and the other brittle, was investigated with the aim of analyzing the influence of the employed resin on the fatigue delamination behaviour of both composites. In the case of dynamic loading, the number of cycles necessary for the onset of delamination was determined for a given elastic energy release rate and crack growth rate for different critical energy rates. The double cantilever beam (DCB) test was found to be suitable for promoting the initial delamination. The experimental results confirm the enhanced performance of the tough resin both in terms of crack initiation and growth rate.

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Fractography and failure mechanisms in static mode I and mode II delamination testing of unidirectional carbon reinforced composites

Cited by 76 publications

References 14 publications

Hygrothermal effects on mode II interlaminar fracture toughness of co‐bonded and secondary bonded composites joints

Hygrothermal effects on mode II interlaminar fracture toughness of co‐bonded and secondary bonded composites joints

Fractografia de Compósito Estrutural Aeronáutico Submetido ao Ensaio de Tenacidade à Fratura Interlaminar em Modo II

Influence of the Matrix Type on the Mode I Fracture of Carbon-Epoxy Composites Under Dynamic Delamination

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