CompositesWorld

MAR 2017

CompositesWorld

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MARCH 2017 54 CompositesWorld Critical: Winding pattern + material selection The design process considers multiple performance factors to optimize the fiber winding pattern. QA1 employs a modified epoxy resin that contains silica nanopar- ticles, supplied by 3M Aerospace and Commercial Transportation Div. The additive significantly increases shaft longitudinal and hoop stiffness and delivers higher abrasion resistance, compared to conventional epoxy resin systems. Wound, inspected and tested with care Driveshafts are produced on a McClean Anderson-supplied filament winding machine, and oven-cured in-house. Each driveshaft undergoes microscopic inspection, mechanical testing and torsion testing, before delivery. Market focus: Performance upgrades An all-composite, filament-wound driveshaft fabricated by QA1 is installed in a performance car, replacing a metal driveshaft. FOCUS ON DESIGN torsional stiffness, and torsional frequency — the latter is a recent addition that is still being validated. All 12 of the constants are used in generating laminate-wide stress/strain responses from various directional loads," explains Neubauer. e software used for all finite element analysis (FEA) and inertia calculations is SolidWorks Simulation, supplied by Dassault Systèmes SolidWorks (Waltham, MA, US). Says Neubauer, "We also use a numerical model that is implemented in Microsoft Office's native scripting language, Visual Basic for Applications (VBA). is allows us to take advantage of Excel's solvers [Evolutionary, GRG-Nonlinear, Simplex LP] to generate optimized laminates given certain criteria." Modal analysis also is conducted to determine natural frequencies and thus the minimum required shaft stiffness. Ultimately, the design process produces fiber winding patterns, tube diameter and wall thickness for a customer's specific requirements and performance factors. Although the winding patterns and ply sequence used for each customer or market application are strictly proprietary, generally, the following parameters apply: Axial (0-35°) fibers tend to increase critical speed; helical winding angles of 35-55° tend to increase torsional stiffness; high fiber angles of 55-90° (hoop) tend to increase buckling torque. A lower winding angle of 20-30° might be chosen if torsional "softness" would be desirable, that is, the shaft would allow a slight axial twist to withstand abrupt power input. "e combina- tion of our design software tools allows us to go through an itera- tive development process fairly quickly," adds Gorsuch, "and we can design, fabricate and test shafts in a relatively short period, to confirm our computer modeling." He adds that QA1's driveshaft designs are symmetrical with balanced layups, to ensure even stress distribution and balance, with wall thicknesses ranging from 2.5 to 8 mm. Nanotech for better performance, big benefits QA1's design efforts, however, go beyond careful attention to the critical reinforcement. "e axial and hoop moduli of a shaft are dependent not only on the winding pattern, but also on the resin matrix modulus," Gorsuch points out, "which strongly affects lamina transverse and shear stiffnesses." QA1 has worked closely with 3M Aerospace and Commer- cial Transportation Div. (St. Paul, MN, US) to test and develop a version of 3M's 4831 epoxy, which contains silica nanoparticles, for all of its products. Gorsuch says the nanosilica, added at 30-40 wt/%, significantly increases shaft longitudinal and hoop stiff- nesses for a fixed winding pattern, fiber type and fiber content, and it also produces a more durable product with greater abrasion resistance than one made with an unmodified resin. QA1 typically uses T700 standard-modulus polyacryloni- trile (PAN) carbon fiber from Toray Carbon Fibers America Inc. (Flower Mound, TX, US), but other fiber types are always under evaluation, including those from Mitsubishi Rayon Carbon Fiber and Composites Inc. (Sacramento, CA, US), DowAksa USA (Marietta, GA, US) and Hyosung Corp. (Seoul, Republic of Korea).

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