Author(s): Harun Bayraktar, Igor Tsukrov, Michael Giovinazzo, Jon Goering, Todd Gross, Monica Fruscello, Lars Martinsson

Presented At: SAMPE 2012, Baltimore, MD

Publication Date: May 2012

Three-dimensional woven composites that are becoming increasingly popular in aerospace applications have superior through-the-thickness strength, stiffness, and thermal conductivity compared to conventional 2D laminated composites. However, despite their advantages, many details regarding the mechanical behavior of 3D woven composites are not as well-known as they are for traditional laminated composites. Microcracking of carbon-epoxy composites during resin curing is one important example. The main goal of this study is to improve the understanding of cure-induced microcracking through the development of realistic numerical models validated with experimental data. Specifically, microcracking predictions of unit cell finite element models of two different fiber architectures are compared with results of micro-computed tomography scans of actual panels with the same fiber architectures. The curing process is simulated using thermal stress analysis and numerical predictions of the stress concentration areas correlate well with the observations of microcracking obtained by micro-computed tomography.

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Author(s): Mike McClain and Jonathan Goering

Presented At: SAMPE 2012, Baltimore, MD

Publication Date: May 2012

3D weaving is a manufacturing technique for producing near net shape fiber preforms. These preforms can be processed into composite components using liquid molding techniques such as resin transfer molding (RTM) or the vacuum assisted process (VAP®). One of the main advantages of 3D woven preforms is that the touch labor required to assemble them is minimal, leading to rapid and highly automated preform construction. This paper describes an application which uses 3D woven preforms as building blocks in a more complicated fiber preform assembly. Details of the construction of the individual 3D woven preforms, their assembly into larger preforms, and estimates of labor savings relative to conventional laminated construction are discussed.

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Author(s): Michael McClain and Jonathan Goering

Presented At: Society of Manufacturing Engineers’ (SME) Composites Manufacturing 2012

Publication Date: March 2012

Three dimensional woven composite structures are slated to provide significant weight savings on the next generation of engines for commercial aircraft. The inherent toughness of these structures, the weight savings and the ability to weave near net shapes were key drivers in their selection for these applications. This discussion will provide an overview of the 3D weaving process as well as a summary of recent work in the area of 3D composite and preform fabrication. On-going work currently focuses on using the technology to fabricate beams and frames. Of particular interest is the fabrication of sine wave beams that do not require the darting associated with prepreg type structures.

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Author(s): Harun Bayraktar, Jon Goering, Monica Fruscello, Lars Martinsson, Michael Giovinazzo, Igor Tsukrov, Todd Gross

Presented At: 52nd AIAA Structures, Structural Dynamics and Materials Conference, Denver, CO

Publication Date: 2011

Despite their many advantages in performance, manufacturing, and cost, many details regarding the mechanical behavior of 3D woven composites are not as well known as they are for traditional laminated composites. Cure-induced microcracking that can occur in 3D woven composites with certain fiber architectures and resins is one important example. The main goal of this study was to develop experimentally validated realistic finite element models to better understand this phenomenon and predict microcracking. Another goal was to validate the use of micro-computed tomography (μCT) to detect microcracking within 3D woven composites. Our results show that μCT technology can be successfully used to detect microcracking and that microcracking is more prevalent in “orthogonal” fiber architectures with increased through-thickness reinforcement. Consistent with this, the numerical models for “ply-to-ply” architectures with little through-thickness reinforcement do not predict microcracking which was confirmed by μCT scans. Difficulties encountered in modeling orthogonal architectures and future work to overcome these are also discussed. (paper purchased as part of full conference proceedings)

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Author(s): Igor Tsukrov, Harun Bayraktar, Michael Giovinazzo, Jon Goering, Todd Gross, Monica Fruscello, Lars Martinsson

Author(s): Goering, J., and McClain, M.

Presented At: 2010 SAMPE Spring Conference, Seattle, WA USA

Publication Date: 2010

Several concepts for fiber preforms that can be processed into composite beams using an out-of-autoclave process, such as conventional or vacuum assisted resin transfer molding, are presented. These preforms are intended for use in aerospace structures such as floor beams, and utilize 3D weaving to produce components that require less hand labor and improve performance relative to a conventional 2D fabric or pre-preg tape layup. One concept uses a special Pi preform with upstanding legs that follow a sine wave to produce a sine wave web beam, and another uses integrally woven elements to produce a truss structure. Prototypes of each concept were woven from carbon fiber and molded using epoxy resin. Lessons learned during this fabrication are discussed, and additional candidate applications are identified. The performance of the prototype beams was assessed analytically and is compared to that of a conventional laminated beam. The results of this analysis are presented for equal weight designs that are critical in web bucking.

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Author(s): McClain, M., Goering, J., and Rowles, C.

Presented At: SAMPE 2009, Baltimore, MD USA

Publication Date: May 18-21, 2009

Previous work has successfully demonstrated the feasibility of Stretch Broken Carbon Fiber (SBCF) to replace continuous fiber in 3D preforms without major alterations to the weaving set-up and processing parameters, Form both inner and outer stiffeners of typical aircraft frames while maintaining fiber alignment in radial and longitudinal directions without darting, and Be utilized in Resin Transfer Molding (RTM) for both epoxy and BMI resins. To further improve the structural efficiencies and manufacturability of such frames, Albany Engineered Composites (AEC) examined methods to increase SBCF utilization. AEC investigated the viability of SBCF in tailored woven preforms known as variable geometry pi from a weaving and forming standpoint. This pi, as the name implies, changes geometry along the length to locally suit the applied loads. AEC is also investigating bead-stiffened webs formed with SBCF. The bead stiffeners prevent localized buckling, increase shear strength, and reduce the overall thickness and weight of the web.

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Author(s): Goering, J., and McClain, M.

Presented At: American Society for Composites, 22nd Technical Conference, Seattle, WA USA

Publication Date: September 17-19, 2007

This paper describes recent advancements in the fabrication and forming of three dimensionally woven 'Pi' inserts. Two main types of preform are presented; 1) preforms that have variable cross sections (i.e. variable thickness and/or variable clevis width), and 2) preforms that can be formed to curved shapes through the use of stretch broken carbon fiber. (paper may be purchased as part of full conference preceedings)

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