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Comparison of fiber microstructural characteristics for two grades of carbon fiber composites

: Stapleton, S.E.; Schey, M.J.; Przybyla, C.P.; Uchic, M.; Krieger, H.; Appel, L.; Zabler, S.

Volltext ()

Waas, A. ; American Society for Composites -ASC-:
American Society for Composites - Thirty-Third Technical Conference on Composite Materials 2018. Proceedings : September 24-26, 2018, Seattle, Washington
Lancaster, Pa.: DEStech Publications, 2018
ISBN: 978-1-60595-534-6 (Originalausgabe)
ISBN: 978-1-5108-7207-3 (Curran)
American Society for Composites (ASC Technical Conference) <33, 2018, Seattle/Wash.>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer IIS ()

One of research thrusts to push the limits of advanced fiber reinforced composites is to determine the link between manufacturing, resulting microstructure, and final structural properties. By bridging the gap between these topics, not only can we better understand how and why composites structurally work as they do, but we can potentially tailor the manufacturing processes for a desired resultant set of properties. To better illuminate the effects of manufacturing on microstructure and microstructure on properties, computational models are often employed. Using these models, we can gain insight on relationships that may otherwise remain unexplored. This research thrust is often labelled as ICME, integrated computational materials engineering. One important aspect of ICME is to capture the variation of the microstructure and how this variation effects final properties. The variation usually occurs either in local material properties of the constituents or a variation of the spatial distribution of constituents. For fiber reinforced composite materials, this spatial variation has mainly been introduced into micro-mechanical models by varying the fiber arrangement in a 2D cross-section. However, simply varying the spatial placement of 2-D fibers neglects the real origin of microstructural variation, which is to be found in the 3-D interaction of fibers with their neighbors[1, 2]. One sees examples of this in interfaces between plies of different orientations, where the fibers at the edge are not aligned with each other and the fibers from a layer cannot integrate/interpenetrate into the neighboring layer: resulting in a resin-rich region and poor interlaminar properties. Furthermore, a few stray fibers within a densely packed region can cause a loosely-packed envelope around the path of the stray fibers [3]. There is speculation that this interaction of fibers with each other in a 3-D context can have important implications on properties such as fracture toughness, fiber bridging [4], and compaction limitations. In this work, the spatial variation of two different microstructures is compared both qualitative and quantitatively. One scan is from an aerospace-grade laminate, made from a prepreg in an autoclave using more expensive materials and manufactured for higher performance. The second scan comes from an automotive-grade heavy tow (48k fibers per tow) consolidated using VARTM, where the reduced cost of working with a larger tow results in more entanglement of fibers. The scans were analyzed to extract fiber centerline paths, and different statistical descriptors were extracted to compare volume fraction distribution, off-axiality, entanglement, etc. By comparing two composites of similar materials with vastly different manufacturing histories, the link between manufacturing and microstructure can begin to be forged.