Braided quasi-isotropic (0°, +/-60°) fabric has not only allowed easy lay-up but has also provided excellent performance for a wide range of composite applications. However, to date the test data characterizing the benefits of quasi-isotropic fabric has been application specific. Quasi -isotropic laminates are composed of prepregged woven fabric and these were compared to laminates containing prepregged quasi-isotropic braided fabric. Both types of fabrics were developed using the same fiber type and even prepregged with the same resin.
The coupon test matrix included CAI; in-plane shear; tension and compression in multiple directions; and open-hole tension and open-hole compression. Panel testing comprised of impact testing using a soft gelatin projectile. The containment threshold was bracketed through this panel testing.
Braid has increasingly become a standard reinforcement in advanced composite structures beginning in the early 1990s. Originally used in the industrial and recreational markets, the performance of the composite system was generally measured at the full scale product level. As use of the material extended to the aerospace segment, a large number of material property characterization programs were performed by industry at the coupon level in order to qualify product performance.
Industry characterization mostly included impact testing to measure the impact performance benefits that are usually achieved with braid reinforced composites. Traditionally, not much information was available on this in the public domain, and most of this characterization work (coupon and impact) was largely informed by the research conduct on test methods at NASA Glenn in Cleveland, Ohio [ref. 1,2,3]
Until now, a large part of product developments for braid reinforced structures were intended for resin infused composites. However, recent development efforts with TenCate Advanced Composites have led to successful production of a pre-impregnated form of braided fabric. The subject of this study is QISO/ TC275-1 triaxial quasi-isotropic (0°, +/ -60°) braided fabric pre-impregnated with a high performance epoxy resin.
The study analyzed both light (3K, 272 gsm) and heavy (12K, 536 gsm) braided Qiso architectures. Each of the braided fabric was benchmarked against laminates reinforced with a woven architecture. Extreme care was taken to prevent variables between the woven and braided laminates other than the fabric architecture.
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1. Wood, Geoff. “Quasi-isotropic braid reduces cost in large composite tooling.” JEC Composites Magazine 53 (2009): 46-47.
2. Roberts, G., Pereira, M., Braley, M., Arnold, W., Dorer, J. & Watson, W., “Design and Testing of Braided Composite Fan Case Materials and Components.” International Symposium in Air Breathing Engine. ISABE-2009-1201, 2009.
3. Kohlman, Lee. “Evaluation of test methods for triaxial braid composites and the development of a large multiaxial test frame for validation using braided tube specimens.” Dissertation University of Akron. May 2012.
This information has been sourced, reviewed and adapted from materials provided by TenCate Advanced Composites.
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