Investigation of the Effect of Part Length on Process-Induced Fiber-Wrinkled Regions in Composite Laminates

Kugler, Danielle; Joyce, Peter; Moon, Tessie J

doi:10.1177/002199839703101703

Cited by 21 publications

(21 citation statements)

References 15 publications

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“…In order to more fully characterize this waviness and determine which processing parameters most affected it, a series of experiments was performed. The first of these experiments studied the effect of laminate length on fiber waviness, and the results indicated that length had little affect on waviness as long as the length was greater than a threshold value required for waviness initiation [5,36]. In order to further investigate the effect of processing on fiber waviness, two more experiments were performed; the first investigated the effect of hold temperature and tool plate material on waviness development and the second investigated the effect of cooling rate and tool plate material on waviness development.…”

Section: Preliminary Workmentioning

confidence: 99%

Identification of the Most Significant Processing Parameters on the Development of Fiber Waviness in Thin Laminates

Kugler

Moon

2002

Journal of Composite Materials

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This paper identifies the material and processing parameters which most significantly influence the development of in-plane waviness in laminates. Thin laminates of unidirectional, T300 carbon-fiber/polysulfone matrix prepreg were processed in an autoclave and a custom-made water-cooled chamber, which allowed fast cooling rates. Multivariate regression analysis of process-induced waviness was performed for combinations of the select process variables and their interactions to identify those factors responsible for waviness development. Of the eight parameters investigated – hold temperature, hold time, pressure, length, width, thickness, cooling rate, and tool plate material – only three affected the development of fiber waviness: length, cooling rate, and tool plate material. Length affects not only the number of wrinkles and wrinkle distribution, but also the average amplitude of the waviness. Cooling rate affects the wavelength and amplitude of the waviness, as well as the number of wrinkles. Tool plate material primarily affects the number of wrinkles, without showing a significant effect on the average wave geometry. There is also an interaction between tool plate material and cooling rate in producing fiber waviness. For the three relevant parameters, the possible waviness-inducing mechanisms are tool plate/part coefficient of thermal expansion (CTE) mismatch, temporal temperature gradients (or cooling rates), and spatial temperature gradients. The tool plate/part CTE mismatch proved to be the most important mechanism driving fiber waviness in plates, although changes in cooling rates also dramatically affected the quantity of waviness which developed. Spatial temperature gradients were negligible for this study. The tool plate/part CTE mismatch-driven axial buckling loads on the fibers were substantial in the outermost laminate plies, or skin, but negligible in the laminate core. Waviness was limited to the surface or skin plies, even in identically-processed thick laminates. This study confirmed that if the fibers experience axial loads – albeit a small fraction of their Young’s modulus – while the matrix is unable to provide some level of transverse fiber support, the fibers will microbuckle resulting in waviness (in-plane or out-of-plane depending upon the laminate constraint).

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Section: Preliminary Workmentioning

confidence: 99%

Identification of the Most Significant Processing Parameters on the Development of Fiber Waviness in Thin Laminates

Kugler

Moon

2002

Journal of Composite Materials

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“…A global increase in undulation is another possible reaction of the fiber bed. 11,12 Undulation, fiber misalignment, and in-plane waviness are usually integrated into the parts' strength evaluation by means of knockdown factors. 7 Outof-plane wrinkling, however, has a significant influence on strength, stiffness, and fatigue behavior with strength reductions of up to 70% under a four-point bending load.…”

Section: Introductionmentioning

confidence: 99%

“…Laminate lay-up and mechanical properties 3,5,8,22 . Tool-part interaction and interlaminar friction 4,8,11,12,23 . (Pre-)compaction 5,12,21,28,29 .…”

Section: Introductionmentioning

confidence: 99%

An experimental characterization of wrinkling generated during prepreg autoclave manufacturing using caul plates

Weber

Englhard

Arent

et al. 2019

Journal of Composite Materials

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Out-of-plane ply wrinkling is a major quality issue for carbon fiber reinforced prepreg parts. Its triggers are numerous and not every influencing parameter is fully understood, yet. The research presented in this paper aims at providing a better insight into ply wrinkling generated during autoclave compaction using caul plates. A detailed description of the experimental set-up and the applied methodology is provided. Statistical analyses of varying influencing factors such as part thickness, geometry, tool–part interaction, and laminate lay-up are presented. This, in turn, generates a better understanding of their impact on fiber wrinkling risk and size. Part geometry and compaction deformation show the most significant influence on wrinkle size. However, for the given manufacturing concept, tool–part interaction also plays a significant role. It influences both the dimension and location of the wrinkles, as well as the existence and size of a critical flange length of the part. A noteworthy effect on wrinkle generation and size can also be observed when adding unidirectional plies to an otherwise fabric laminate.

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“…Some have attributed the causes of fiber waviness in composites to the relationships between the mandrel and pressure considerations during cure [15,16] . Precure and postcure optical and ultrasonic techniques have been proposed for characterization with some success [15,[17][18][19][20] .…”

Section: Introductionmentioning

confidence: 99%

An Infrared Thermoelastic Stress Analysis Investigation for Detecting Fiber Waviness in Composite Structures

Elhajjar

Haj-Ali

Wei

2014

Polymer-Plastics Technology and Engineering

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A full-field thermoelastic stress analysis infrared (TSA-IR) method is used to investigate the possibility of inspecting for out of plane fiber waviness in composite structures. Two different waviness profiles are generated and compared to control specimen having no anomalies. Tension and compression loading schemes are investigated and the TSA-IR emissions are compared to cross-sectional investigations. A subset of the specimens is also notched to investigate the thermal emissions from holes when compared to the waviness. The interaction of the hole and waviness shows the errors that can be introduced when using TSA-IR for quantitative analysis.

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Investigation of the Effect of Part Length on Process-Induced Fiber-Wrinkled Regions in Composite Laminates

Cited by 21 publications

References 15 publications

Identification of the Most Significant Processing Parameters on the Development of Fiber Waviness in Thin Laminates

Identification of the Most Significant Processing Parameters on the Development of Fiber Waviness in Thin Laminates

An experimental characterization of wrinkling generated during prepreg autoclave manufacturing using caul plates

An Infrared Thermoelastic Stress Analysis Investigation for Detecting Fiber Waviness in Composite Structures

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