An experimental study of defect evolution in corners by autoclave processing of prepreg material

Netzel, C.; Mordasini, A.; Schubert, J.; Allen, Tom; Battley, Mark; Hickey, Christopher; Hubert, Pascal; Bickerton, Simon

doi:10.1016/j.compositesa.2021.106348

Cited by 24 publications

(15 citation statements)

References 13 publications

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“…Hubert et al [72] determined that the thickening of a corner tend to occur with a concave tool contrary to the convex shape that induces the thining explained by two different mechanisms in their later work [73]. The first being the corner/flange pressure variation, where the resin accumulates and flows to the corner due to its locally low pressure [74] and the second being the inter-ply friction. Hallander et al [75] determined the influence of the interlayer friction by changing the fiber orientation and implanting a veil on the outcome of the forming procedure of the unidirectional (UD) laminate composite with mixed ply materials formed into the C-channel.…”

Section: A) Out Of Plane Deformationmentioning

confidence: 99%

Composite preforming defects: a review and a classification

2021

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Advancing in the process of extending the use of composites for structural parts applications, it is inevitable to work on complex shapes. That is the main reason why understanding the complex forming mechanisms and the factors put into play during the process of composite materials is a major interest for both pre-impregnated forming and dry fabric preforming. Thus, the apdpearance of defects is a major concern and predicting their appearance for optimal product quality is the priority. A great number of authors showed that defects degrade the overall performance of the composite by creating local heterogeneities. Many factors can initiate these defects. This article is an assembly of the development of the literature on this subject. It is an attempt to provide a description for each defect and a classification order following the scale, the behavior mechanisms, the appearance plan. This will help to converge toward an identification of the defects manifesting during the composite forming.

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Section: A) Out Of Plane Deformationmentioning

confidence: 99%

Composite preforming defects: a review and a classification

2021

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“…Specifically notable are combination of multiple defects as observable in Figure 1 (a) -(c). In Figure 1 (a), taken from the recent study by Netzel et al [7] looking into the influence of environmental variable on the defect formation in corner pieces, a fairly simple wrinkle pattern can be observed in combination with a singular void. Far more complex states are shown in Figure 1 (b), where both wrinkling and in-plane waviness combine with resin pockets.…”

Section: Wrinkles In Realistic Partsmentioning

confidence: 99%

“…Similarly, studies investigating the formation of wrinkles, including those experimental specimens were produced for which more complex morphologies could be observed (e.g. Netzel et al [7]), still only extracted either height or width separately [8,[14][15][16], the aspect ratio [7], the maximum angle [17,18], or a spatial distribution of angles [19]. A notable exception to these experimental studies is the work by Hayman et al who included the height, width, and maximum angle in the characterisation of wrinkles in their study on sandwich panels [20].…”

Section: Wrinkles In the Literaturementioning

confidence: 99%

The Effect of Out-of-Plane Waviness Asymmetry on Laminate Strength

Maes¹,

Elsaid²,

Hallett³

et al. 2021

American Society for Composites 2021

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The study of defects and their influence on the performance of composite structures is well documented. However, simplifications are often made regarding the morphology of these defects. As part of the CerTest project, a database of composite features and defects is being built, for which an assessment must be made of what information is relevant. This study looks specifically at out-of-plane waviness and seeks to investigate whether the commonly used severity metrics (e.g. maximum angle) are sufficient to characterize such defects when considering more complex morphologies. To assess this, previously developed numerical methods are used to investigate the tensile and compressive strength of cross-ply and quasi-isotropic laminates. These laminates are seeded with asymmetrical out-of-plane waviness. The numerical results demonstrate that for reliable prediction of the strength reduction caused by out-of-plane waviness, the asymmetry is an important consideration with relative reductions from symmetric to asymmetric wrinkle of up to 50% found within the wrinkles evaluated in this study.

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“…5,[17][18][19][20] Recently, an experimental approach has shown a strong causal link between local material health and the type of part being consolidated. 18 The geometry of the tooling in vacuum bag consolidation can create delaminations or crackings in very localised areas of the part. However, there is a lack of numerical models to understand the local evolution of stress, strain and material health.…”

Section: Introductionmentioning

confidence: 99%

Thick thermoplastic composite laminate consolidation: Experimental observations and numerical approaches

Denis

NGuyen

Lecointe

et al. 2022

Journal of Composite Materials

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Since the benefits of composite materials have been demonstrated, particularly those relevant to the fields of transports and energy, increasingly high industrial expectations are emerging. As the control of the processes is complex, the thickness of the composite materials does not usually exceed a few millimetres. The aim of the work presented in this paper is to highlight new phenomena related to the oven/autoclave consolidation of thicker thermoplastic composites. In the case of such thick composites, the influence of certain phenomena that are usually neglected becomes important and a physical interpretation becomes necessary (the thermal contact resistance between mold and part and the influence of mold geometry). Here, an experimental approach is compared with numerical simulations of heat transfer and crystallization in order to validate the proposed thermokinetics model. Finally, some numerical observations are discussed and analyzed.

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An experimental study of defect evolution in corners by autoclave processing of prepreg material

Cited by 24 publications

References 13 publications

Composite preforming defects: a review and a classification

Composite preforming defects: a review and a classification

The Effect of Out-of-Plane Waviness Asymmetry on Laminate Strength

Thick thermoplastic composite laminate consolidation: Experimental observations and numerical approaches

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