Heterogeneity of discontinuous carbon fibre composites: Damage initiation captured by Digital Image Correlation

Johanson, Kerry; Harper, L.T.; Johnson, M. S.; Warrior, N.A.

doi:10.1016/j.compositesa.2014.10.014

Cited by 42 publications

(25 citation statements)

References 37 publications

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“…[14][15][16][17][18][19] Thus, the observed stress concentration resulted in the appearance of the largest microcrack, which subsequently expanded due to the chain reaction and finally caused specimen's fracture.…”

Section: Optical Microscopy Studiesmentioning

confidence: 97%

Experimental characterization of the tensile failure mode of ultra-thin chopped carbon fiber tape-reinforced thermoplastics

Yamashita

Hashimoto

Suganuma

et al. 2016

Journal of Reinforced Plastics and Composites

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Ultra-thin chopped carbon fiber tape-reinforced thermoplastics, which belong to a class of randomly oriented strands and are characterized by enhanced strength, stiffness, and formability properties, have been prepared via a paper-making method from ultra-thin thermoplastic prepregs. The failure of ultra-thin chopped carbon fiber tape-reinforced thermoplastics under static tensile loading was studied in detail using various observation techniques, such as high-speed camera imaging, thermography, and optical microscopy. The obtained results revealed that the tensile fracture of ultra-thin chopped carbon fiber tape-reinforced thermoplastics exhibited three main patterns: fiber breakage, splitting of chopped tapes, and pulling out of chopped tapes. In contrast to conventional randomly oriented strands, the utilization of ultrathin prepregs decreased the tensile strength scattering. An increase in the ultra-thin prepreg tape length resulted in an increase in the strength average magnitude, reaching saturation at a length of 18 mm. The results of this study can be used for constructing tensile strength prediction models and expanding the ultra-thin chopped carbon fiber tape-reinforced thermoplastics application range.

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Section: Optical Microscopy Studiesmentioning

confidence: 97%

Experimental characterization of the tensile failure mode of ultra-thin chopped carbon fiber tape-reinforced thermoplastics

Yamashita

Hashimoto

Suganuma

et al. 2016

Journal of Reinforced Plastics and Composites

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“…The chips are then sandwiched between two resin sheets, which are subsequently attached together by heating. A different approach, called the directed carbon fiber preform process (DCFP), is also applied in SMC fabrication . Chips are initially deposited onto a region from a revolving chopper head along a series of linear paths.…”

Section: Introductionmentioning

confidence: 99%

“…Wan et al conducted a fractographic analysis of UT‐CTT, and the result indicates that the obtained elastic modulus is almost independent of both the tape length and molding pressure, while the tensile and compressive strength exhibits high molding pressure sensitivity. Johanson et al found significant variation in the strain field between two surfaces of DCFP composites during tension after detailed comparison of strain field taken immediately prior to failure. However, further mechanical analysis is needed to describe the specific effects of microstructural variations.…”

Section: Introductionmentioning

confidence: 99%

“…Several types of defects were detected, such as macro‐voids, fiber kinking, swirling or resin‐rich areas, but failure may or may not occur in proximity to these hot spots. Johanson et al pointed out that, at lower applied load, there are so many distinct points with higher‐than‐average local strain values in the DIC strain images which makes it difficult to identify the failure location. Currently, the failure location in chopped chip‐reinforced SMC material still cannot be determined efficiently.…”

Section: Introductionmentioning

confidence: 99%

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Correlation between failure and local material property in chopped carbon fiber chip‐reinforced sheet molding compound composites under tensile load

et al. 2018

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To develop further understanding towards the role of a heterogeneous microstructure on tensile crack initiation and failure behavior in chopped carbon fiber chip‐reinforced composites, uni‐axial tensile tests are performed on coupons cut from compression molded plaque with varying directions. Experimental results indicate that failure initiation is relevant to the strain localization, and a new criterion with the nominal modulus to predict the failure location is proposed based on the strain analysis. Furthermore, optical microscopic images show that the nominal modulus is determined by the chip orientation distribution. At the area with low nominal modulus, it is found that chips are mostly aligning along directions transverse to loading direction and/or less concentrated, while at the area with high nominal modulus, more chips are aligning to tensile direction. On the basis of failure mechanism analysis, it is concluded that transversely oriented chips or resin‐rich regions are easier for damage initiation, while longitudinally oriented chips postpone the fracture. Good agreement is found among failure mechanism, strain localization and chip orientation distribution. POLYM. COMPOS., 40:E962–E974, 2019. © 2018 Society of Plastics Engineers

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“…This is of particular interest for automotive components, which are typically driven by stiffness rather than strength. The addition of the UD plies will significantly improve the tensile stiffness, but improvements in tensile strength are limited due to stress concentrations in the ASMC [10]. The UD fibres are more effective in bending however, as they are typically located at the surface of the plaque and therefore further from the neutral axis.…”

Section: Introductionmentioning

confidence: 99%

Compression moulding of composites with hybrid fibre architectures

Corbridge

Harper

Focatiis

et al. 2017

Composites Part A: Applied Science and Manufacturing

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Advanced Sheet Moulding Compounds (ASMC) and unidirectional (UD) prepregs have been co-compression moulded to form a hybrid composite material. In-mould flow influences the UD fibre architecture in two ways. When UD fibres are aligned transversely to the ASMC flow direction, shearing occurs which causes local changes in fibre volume fraction and fibre waviness. When the UD fibres are aligned with the ASMC flow direction, ply migration takes place. In general, the composite stiffness follows a rule of mixtures relationship, with the stiffness proportional to the UD fibre content.A grid analysis method has been developed to quantify distortion in the UD plies. Staging the resin to 50% cure was shown to reduce ply distortion during moulding, whilst maintaining suitable inter-laminar shear strength. Adding an interfacial prepreg ply between the reinforcing UD fibres and the ASMC charge successfully prevented distortion in the UD fibres, avoiding shear thinning and fibre migration.

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Heterogeneity of discontinuous carbon fibre composites: Damage initiation captured by Digital Image Correlation

Abstract: 10

Cited by 42 publications

References 37 publications

Experimental characterization of the tensile failure mode of ultra-thin chopped carbon fiber tape-reinforced thermoplastics

Experimental characterization of the tensile failure mode of ultra-thin chopped carbon fiber tape-reinforced thermoplastics

Correlation between failure and local material property in chopped carbon fiber chip‐reinforced sheet molding compound composites under tensile load

Compression moulding of composites with hybrid fibre architectures

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