Damage progression and defect sensitivity: An experimental study of representative wrinkles in tension

Bloom, L. D.; Wang, Jinhuo; Potter, Kevin D

doi:10.1016/j.compositesb.2012.05.021

Cited by 111 publications

(77 citation statements)

References 7 publications

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“…Although waviness can theoretically be formed through this mechanism, most practical geometries induce local wrinkling in LCM (Dodwell et al, 2014;Khan et al, 2015). For instance, wrinkling is commonly reported and most critical in the thick, load carrying sections of wind turbine blades, such as the spar caps (Altmann et al, 2015;Bloom et al, 2013). Wrinkling has been also reported to be more pronounced in other thick LCM parts with complex shapes, extensively used in large wind turbine blades, submersibles, and aerospace platforms (Altmann et al, 2016;Khan et al, 2016).…”

Section: Fiber Undulation Formation In Lcmmentioning

confidence: 99%

“…For example, forcing a slightly oversized preform into a mold cavity has been reported to induce both fiber waviness and wrinkling (Altmann et al, 2016;Bloom et al, 2013). These wrinkles tend to be localized such as those occasionally observed on composite wind turbine blade skins (Bloom et al, 2013).…”

Section: Fiber Undulation Formation In Lcmmentioning

confidence: 99%

“…These unwanted deformations of fiber preforms include preform misalignment, waviness, and wrinkling. Wrinkling and waviness are often used interchangeably and considered to be a type of fiber misalignment that indicates preform defects within the composite parts (Bloom et al, 2013;Fedulov et al, 2015). For clarity, a distinction is made in this article.…”

Section: Defect Types In Lcmmentioning

confidence: 99%

“…Likewise, Horrmann et al (2016) reported severe influence on the static strength and on the fatigue life of unidirectional carbon/epoxy RTM composites. Bloom et al (2013) reported up to 40 % reduction in tensile strength due to localized wrinkles in glass/ epoxy composites. Garnich and Karami (2005), on the other hand, reported that wrinkling can lead to a decrease of as much as 80 % in the longitudinal modulus of elasticity along the expected direction of the fibers.…”

Section: Adverse Effects Of Fiber Undulation On Mechanical Propertiesmentioning

confidence: 99%

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Process Induced Defects in Liquid Molding Processes of Composites

Hamidi

Altan

2017

International Polymer Processing

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Liquid Composite Molding (LCM) processes are cost efficient manufacturing alternatives to traditional autoclave technology for producing near-net shape structural composite parts. However, process induced defects often limit wider usage of LCM in structural applications. Thorough knowledge of these defects, as well as their formation mechanisms and prevention techniques, is essential in developing improved LCM processes. In this article, process induced defects in liquid molding processes of composites, categorized into preform, flow induced and cure induced defects, are reviewed. Preform defects are further presented as fiber misalignment and fiber undulation (waviness and wrinkling). The respective causes, detrimental effects, and possible prevention methods of these defects are presented. Thereafter, flow induced defects are classified as voids and dry spots. Dry spot formation mechanisms in LCM processes and available prevention techniques are summarized. In addition, void formation mechanisms, adverse effects on composite properties, and removal techniques are presented. Cure induced defects include microcracks, void growth and geometrical distortions (warpage and spring-in). Each of these defects are discussed along with their underlying causes as well as their control and reduction schemes.

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Section: Fiber Undulation Formation In Lcmmentioning

confidence: 99%

Section: Fiber Undulation Formation In Lcmmentioning

confidence: 99%

Section: Defect Types In Lcmmentioning

confidence: 99%

Section: Adverse Effects Of Fiber Undulation On Mechanical Propertiesmentioning

confidence: 99%

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Process Induced Defects in Liquid Molding Processes of Composites

Hamidi

Altan

2017

International Polymer Processing

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“…Both RTM and bag moulded parts have been considered and the many processes leading to wrinkle formation have been studied [e.g. 40,41,42,43]. So it can be said with complete clarity that wrinkles are a bad thing; that they cause a very significant reduction in performance in static and fatigue strength, at least when coupons are being tested where the defects are of the same sort of scale as the width of the sample.…”

Section: Introductionmentioning

confidence: 99%

‘But How Can We Make Something Useful Out of Black String?’ The Development of Carbon Fibre Composites Manufacturing (1965–2015)

Potter

2016

The Structural Integrity of Carbon Fiber Composites

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Abstract.This chapter looks at how the manufacturing community responded to the invention of carbon fibres, the first practical, high-modulus, reinforcement to be available as continuous fibres; largely through the lens of the author's personal experience. Whilst it seems axiomatic to us today that we use continuous fibres, most of the composites applications in 1965 used short fibres, for example chopped glass, asbestos, whiskers or linen fibres. To a large extent the narrative of carbon fibre composites manufacturing is the story of how to manipulate continuous fibres into complex geometries; and how to do that cost-effectively without introducing strength reducing defects. Until very recently, when the manufacturing and structural integrity communities have started to interact much more, there has tended to be an almost complete disconnect between the materials, design and manufacturing worlds. This has been the case as much in industry as it has in academia and seems to have been the norm since the very beginnings of the application of carbon fibre composites. The difficulties inherent in manufacturing geometrically complex parts were identified very early in the history of carbon fibre composites. However, it has proven to be very challenging to go beyond identifying problem issues to actually solving them, and that process is by no means complete. There are signs that the composites community may finally be on the right track, with some recent successes pointing towards research directions where design and manufacturing approaches can be unified to deliver reliable and cost-effective parts -only 50 years after the process started.

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Experimental and numerical investigation on flexural performance of carbon fiber reinforced polymer composites with uniform and non‐uniform waviness

2022

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The failure of unidirectional and quasi‐isotropic carbon fiber reinforced polymer composite laminate with uniform and non‐uniform out‐of‐plane waviness defects were examined. Experimental tests and numerical simulations were performed for specimens with and without defects. Specimens with different types of waviness such as uniform embedded, non‐uniform hump and non‐uniform indentation were fabricated for testing their performance under three‐point flexural tests. Optical microscopic images were captured throughout the test to investigate the initiation and progression of failure in laminates. Three‐dimensional finite element (FE) models were built by considering actual specimen and defect geometric configurations obtained from optical microscopy. User material subroutine (UMAT) was developed and implemented in Abaqus/Standard to simulate intra‐ply failures as a continuum damage mechanism. The generated models are used to recognize damage initiation and progression during the flexural test. The experimental observations and FE simulation results are in good agreement for failure loads and damage mechanisms for different waviness cases.

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Damage progression and defect sensitivity: An experimental study of representative wrinkles in tension

Cited by 111 publications

References 7 publications

Process Induced Defects in Liquid Molding Processes of Composites

Process Induced Defects in Liquid Molding Processes of Composites

‘But How Can We Make Something Useful Out of Black String?’ The Development of Carbon Fibre Composites Manufacturing (1965–2015)

Experimental and numerical investigation on flexural performance of carbon fiber reinforced polymer composites with uniform and non‐uniform waviness

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