Optimization of curing cycle in carbon fiber-reinforced laminates: Void distribution and mechanical properties

Hernández, S.; Sket, F.; González, C.; LLorca, J.

doi:10.1016/j.compscitech.2013.06.005

Cited by 118 publications

(116 citation statements)

References 21 publications

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“…In prepreg consolidation experiments, long thin cylindrical voids, which are parallel to the fibres have been discovered, showing the improved visualisation abilities compared to 2-D through-thickness microscopy which would show any such void as a pinhole [31,32]. CT imaging showed similar long thin voids in material prepared from compression-moulded prepregs [34]. The enhanced ability of 3-D volume rendering in CT imaging, to characterise void morphology, compared with 2-D microscopy has been illustrated [33].…”

Section: Introductionmentioning

confidence: 68%

“…The long, thin shape of the yarn voids is similar to the voids characterised in prepreg materials [31,32,34]. Examples of each are shown in 2-D slices of images from SRCT in Fig.…”

Section: Constituent Propertiesmentioning

confidence: 81%

“…The enhanced ability of 3-D volume rendering in CT imaging, to characterise void morphology, compared with 2-D microscopy has been illustrated [33]. Unprecedented quantifications of the distribution and size of individual voids have been achieved with CT imaging [33,34]. However, CT-imaging has not been widely used thus far for the void characterisation of resin-infused composite parts, with the exception of the study by Schell et al [35] that presents 2-D scans of infusion-induced voids, and Vila et al [23] that illustrates in-situ voids imaged during the process of infusion in a single fibreglass roving.…”

Section: Introductionmentioning

confidence: 99%

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High-resolution computed tomography in resin infused woven carbon fibre composites with voids

Sisodia

Garcea

George

et al. 2016

Composites Science and Technology

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Significance of paperRecent efforts in the composites industry towards less-expensive means to produce high-performance parts have often involved optimisation of liquid composite moulding processes such as resin transfer moulding (RTM). The most significant gap in part quality between RTM manufactured parts and traditional autoclave processes is the usually higher void content in the former, arising from the entrapment of bubbles during infusion, and the lower consolidation pressures used during such processes. Many laboratories around the world are working on understanding bubble entrapment and subsequent bubble mobility, so as to optimise RTM processes to reduce the concentration and size of voids. This paper contributes to that understanding with threedimensional examination using CT imaging of the morphology, size, clustering and location of the individual voids in composite parts made with RTM. Most important / novel contributionsThis paper presents visualisation of the voids in a composite part with significantly more statistical information regarding size distribution, orientation and location than has been previously shown in the literature. It also addresses a reinforcement architecture more typical to RTM, an un-balanced weave, than the unidirectional fabrics usually studied in previous work on void formation. Analysing a complex reinforcement along with the enhanced visualisation abilities of the CT-imaging technique allowed novel observations and conclusions regarding voids: 1) As the orientation angle between a reinforcement layer and the resin flow direction increases from parallel to perpendicular, larger voids and a greater number of voids were observed in that layer. This was linked to the resulting greater propensity for fatigue crack propagation between voids in layers transverse to the loading direction. A simple optimisation strategy is thus to infuse in a direction transverse to the expected primary load direction, thus creating the fewest voids in the transverse-to-load direction. 2) Voids accumulate around both the layer interfaces and yarns and are nearly completely absent from the layer thickness between those interfaces and away from yarns. 3) Void distribution follows the orientation of fibres in adjacent layers, suggesting that out-of-plane flow is a significant mechanism in void formation and mobility. 4) Observations 1-3 above all imply that current void formation and mobility models must be expanded from a microscale approach to the laminate scale, in order to focus on out-of-plane bubble movement and yarn bubble entrapment. M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT AbstractTomographic imaging using both microfocus radiation and synchrotron radiation was performed to assess the void defects in resin transfer moulded woven carbon fibre composites. The focus of this study is on characterising the void homology (e.g. local void size and spatial distribution) in relation to weave orientation, infusion direction and potential effects on damage formation in tensile loadin...

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Section: Introductionmentioning

confidence: 68%

“…The long, thin shape of the yarn voids is similar to the voids characterised in prepreg materials [31,32,34]. Examples of each are shown in 2-D slices of images from SRCT in Fig.…”

Section: Constituent Propertiesmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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High-resolution computed tomography in resin infused woven carbon fibre composites with voids

Sisodia

Garcea

George

et al. 2016

Composites Science and Technology

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“…Currently, composite laminates with low void content (i.e. <2%) are most often manufactured by the autoclave process [6][7][8]. Yet the composites industry is increasingly considering lower cost alternative processes such as hot-press molding because autoclave curing is expensive partially due to the high cost of the required equipment [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Effect of laminate edge conditions on the formation of microvoids in composite laminates

Anderson¹,

Altan²

2015

AIP Conference Proceedings

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Abstract. Manufacturing defects such as microvoids are common in thermoset composite components and are known to negatively affect their strength. The resin pressure developed in and the resin flow out from the laminates during cure have been reported to be the primary factors influencing the final void content of a composite component. In this work, the effect of laminate edge conditions during the cure process on the formation of microvoids was experimentally investigated. This was achieved by fabricating eight-ply laminates from TenCate® BT250/7781 prepreg in a hot-press at a constant cure pressure of 170 kPa while limiting the laminate perimeter available for resin flow by 0%, 25%, 50%, 75%, and 100%. The individual plies of these five laminates were conditioned at 99% relative humidity before curing to maximize the moisture present in the lay-up before fabrication. The presence of moisture in the lay-ups was expected to promote void formation and allow the effect of restricting flow at the edges of a laminate to be better identified. The restriction of resin outflow was found to cause the average characteristic void diameter to decrease by 17% and void content to rise by 33%. This phenomenon was identified to be a result of the outflow restriction increasing the number of voids trapped within the laminate and indicates that for laminates cured at low pressures resin outflow is the dominant mechanism for void reduction.

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“…Figure 1 shows the three types of fibres, including glass, carbon, and Kevlar were used in fabricating the specimens. Table 1 illustrates the mechanical properties comprising strength, failure strain, and Young's Modulus of carbon, glass, and Kevlar fibres [11]. The Kevlar fabric used in all composite target constructions was plain-woven Hexcel Aramid (poly-paraphenylene terephthalamide), high-performance fabric Style 706 (Kevlar KM-2, 600 denier) with a real density of 180 g/m 2 .…”

Section: Introductionmentioning

confidence: 99%

The Effects of Stacking Sequence Layers of Hybrid Composite Materials in Energy Absorption under the High Velocity Ballistic Impact Conditions: An Experimental Investigation

Randjbaran¹

2013

J Material Sci Eng

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Optimization of curing cycle in carbon fiber-reinforced laminates: Void distribution and mechanical properties

Cited by 118 publications

References 21 publications

High-resolution computed tomography in resin infused woven carbon fibre composites with voids

High-resolution computed tomography in resin infused woven carbon fibre composites with voids

Effect of laminate edge conditions on the formation of microvoids in composite laminates

The Effects of Stacking Sequence Layers of Hybrid Composite Materials in Energy Absorption under the High Velocity Ballistic Impact Conditions: An Experimental Investigation

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