Residual stresses in thermoplastic composites—A study of the literature—Part II: Experimental techniques

Parlevliet, Patricia; Bersee, H.E.N.; Beukers, Adriaan

doi:10.1016/j.compositesa.2006.07.002

Cited by 135 publications

(110 citation statements)

References 104 publications

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“…Thermal expansion mismatch between fibres and matrix or between layers can induce compressive residual stresses development upon temperature change during manufacture [23][24][25]. Thus initial fibre waviness can appear in the fibrous composite which may advance or delay the onset of microbuckling/kink bands formation [26].…”

Section: Discussionmentioning

confidence: 99%

The effect of fibre volume fraction on the onset of fracture in laminar materials with an array of coplanar interface cracks

Winiarski

Guz

2008

Composites Science and Technology

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Section: Discussionmentioning

confidence: 99%

The effect of fibre volume fraction on the onset of fracture in laminar materials with an array of coplanar interface cracks

Winiarski

Guz

2008

Composites Science and Technology

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“…As a consequence to their multilayered structure they show high anisotropy, which complicates NDT. Defects specific to these materials are holes in the fabric, pores, delaminations, contamination of the surface effectively weakening the material and residual stresses [6][7][8]. Those defects can be found with conventional ultrasound when using high testing frequencies.…”

Section: Defects Detectable With Ondtmentioning

confidence: 99%

Novel trends in optical non-destructive testing methods

Huke

Klattenhoff

Kopylow

et al. 2013

J. Eur. Opt. Soc.-Rapid Publ.

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Non-destructive testing (NDT) describes a wide range of methods for measuring and comparing physical quantities against a nominal condition. In this paper we describe and compare different optical NdT (ONDT)-methods with respect to their characteristics and capability for different measurement tasks. ONDT may be specified in two categories, passive and active. The NDT principles of the first category just use a measurement method like view inspection, elipsometry or reflectometry to detect defects which are easily accessible. The principles of the second category use an excitation force, such as heat or mechanical vibration introduced by transducers to detect hidden defects. This category can be specified into two subcategories. The first subcategory "time-/depth-resolved" includes measurement methods delivering detailed information of the geometric features of a hidden defect. Therefore the excitation of the material and the detection of the reaction have to provide a time step which enables depth-solved measurements. Phase-resolved thermography and laser ultrasound are examples for this category. The second subcategory "Integrating" includes measurement technique coupled with an excitation that enables detection of defects but not evaluation of their geometric features. Examples for these measurement techniques are shearography, reflectometry, vibrometry and thermography coupled with excitation method like simple heating or loading with a constant force. We demonstrate experimental results obtained using methods developed in our institute and highlight directions of further development.

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“…In thin laminates for instance, because out-of-plane motion of the fibers is restricted, waviness is more likely to occur (Kugler and Moon, 2002). In contrast, because thick laminates easily experience large temperature gradients through-the-thickness, wrinkling is often induced (Parlevliet et al, 2007). Defects formed through this mechanism are often global in nature, and undulation may be observed throughout the entire composite component.…”

Section: Fiber Undulation Formation In Lcmmentioning

confidence: 99%

“…Both fiber waviness and wrinkling can originate from the residual stresses generated during the curing due to a mismatch between the coefficients of thermal expansion of the composite constituents (Kugler and Moon, 2002;Meink et al, 2002). The temperature changes experienced by the composite as well as the volumetric shrinkage of the matrix are also reported to induce waviness and wrinkling (Kugler and Moon, 2002;Parlevliet et al, 2007). The difference between thermal expansion coefficients of fiber, matrix, and mold can be several orders of magnitude.…”

Section: Fiber Undulation Formation In Lcmmentioning

confidence: 99%

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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Residual stresses in thermoplastic composites—A study of the literature—Part II: Experimental techniques

Cited by 135 publications

References 104 publications

The effect of fibre volume fraction on the onset of fracture in laminar materials with an array of coplanar interface cracks

The effect of fibre volume fraction on the onset of fracture in laminar materials with an array of coplanar interface cracks

Novel trends in optical non-destructive testing methods

Process Induced Defects in Liquid Molding Processes of Composites

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