Examination of Pre-gelation Behavior in AS4/8552 Prepreg Composites

Duffner, Caitlin; Zobeiry, Navid; Poursartip, Anoush

doi:10.12783/asc33/25974

Cited by 2 publications

(3 citation statements)

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“…The driving force leading to this ply saturation is the surface tension driven capillary action which occurs between the resin and the fibre bed within the core of a ply. The strain drop observed in this work can be linked back to this surface tension effect [22]. For the test presented in this paper, the strain response showed a decrease of -1.34 % between 40 °C and 105 °C.…”

Section: Observed Behaviour In Different Zonessupporting

confidence: 59%

“…Previous work has highlighted that the prepreg is not fully saturated, and there is a variable resin distribution within the fibre bed of AS4/8552 UD prepreg. This leads to self-consolidation within the ply when heated [5,21,22]. The driving force leading to this ply saturation is the surface tension driven capillary action which occurs between the resin and the fibre bed within the core of a ply.…”

Section: Observed Behaviour In Different Zonesmentioning

confidence: 99%

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The Effect of Material Variability on the Pre-Gelation Behaviour of Prepreg Composites

Poursartip¹,

Zobeiry²,

Duffner³

2020

SAMPE 2020 | Virtual Series

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Processes such as forming and AFP have become increasingly popular, and these manufacturing techniques require manipulation of the uncured pre-impregnated thermoset matrix composite material (prepreg). Interest in the initial state or pre-gelation behaviour of prepregs has grown due to these manufacturing trends as well as the increasing recent research connecting this regime to processing defects such as wrinkling and porosity. Historically, the pre-gelation behaviour of prepreg has been relatively unexplored due to the challenges that traditional testing methods have in handling the soft raw prepreg. It is shown here that Digital Image Correlation (DIC) can capture the prepreg behaviour through the entirety of a cure cycle on both a local and global level. This work presents the global response of the prepreg, showing the true pre-gelation response, which differs markedly from what has traditionally been presented as the expected behaviour.Additionally, the variability in local prepreg response can be linked back to local strain variations observed using DIC. With the insight into the variability of a ply and the pre-gelation strain response, the findings in this work emphasize the importance of understanding and accurately capturing the initial prepreg condition.

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Section: Observed Behaviour In Different Zonessupporting

confidence: 59%

Section: Observed Behaviour In Different Zonesmentioning

confidence: 99%

The Effect of Material Variability on the Pre-Gelation Behaviour of Prepreg Composites

Poursartip¹,

Zobeiry²,

Duffner³

2020

SAMPE 2020 | Virtual Series

View full text Add to dashboard Cite

show abstract

“…As temperature is ramped up, the softened friction response is due to a decrease in the shear modulus of the resin. With continual heating, the resin migrates to the core of the plies [16,43,50], allowing for improved fiber intermingling and an increase in dry friction. Therefore, the shear response at low temperature processing is dominated by the resin, whereas at high temperature, the shear response is dominated by fiber-fiber contact.…”

Section: Pre-yield Behaviourmentioning

confidence: 99%

Core Movement During Processing of Sandwich Panels

Pawson¹,

Fernlund²

2019

SAMPE 2019 - Charlotte, NC

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Core movement is a phenomenon that plagues sandwich panel fabrication during autoclave processing. External pressure can result in deformation of the core in its weak, lateral direction. This in turn, drags the facesheet plies inward. Parts displaying notable core movement are unfit for service and must be scrapped. Restraining plies, thereby preventing core movement, has become common practice in industrial processing of sandwich panels. Progress has been made in mitigating the risk of core movement through artificially increasing pressure within the core as well as through development of high friction resin/fiber systems. However, a complete understanding of the physics of the problem is still lacking. The focus of this research is to understand how processing conditions affect core movement and to gain a better understanding of the fundamental nature of core movement. Parameters investigated include, temperature, pressure, and a variety of structural features such as tie downs, core machining stabilization, and core chamfer angles. The problem is investigated using novel techniques. In-situ data collection is performed through use of displacement and in-core pressure sensors. Moreover, the entire event is filmed in real time using an autoclavable camera. This allowed for identification of the exact processing parameters during initiation and progression of core movement. Individual ply movement is determined post-processing. It was shown that failure pressure is dictated by viscosity at lower processing temperatures, but at high temperatures this is no longer the case. This implies a shift in the lubrication regime and alters the mechanics of the problem. A basic mechanical model describing the core movement process is outlined and the conditions necessary for core movement initiation are proposed. It was shown that core movement initiates at the chamfer radius and fluctuates between progressing through the core and down the chamfer edge. The results suggest that friction is the governing mechanism behind core movement initiation, which, if true, has important ramifications for sandwich panel design.

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Examination of Pre-gelation Behavior in AS4/8552 Prepreg Composites

Cited by 2 publications

References 0 publications

The Effect of Material Variability on the Pre-Gelation Behaviour of Prepreg Composites

The Effect of Material Variability on the Pre-Gelation Behaviour of Prepreg Composites

Core Movement During Processing of Sandwich Panels

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