Carbon prepregs that match on paper but come from different suppliers do not give the same limb material

The summary today

There is a single test, Korean, from 2023, and it works on the material, not on a finished bow. Three unidirectional prepregs from three manufacturers, made with the same Toray fibre and the same stated resin content, 38 per cent, were laid up the same way and cured in an autoclave under the same conditions, to build specimens intended for recurve limbs. In tension the three are alike. In bending and compression they are not: one of the three has the highest fibre fraction, the lowest measured resin content and the best strength and modulus, and under the electron microscope the machined surface of another shows numerous pinholes, while the other two are clean. Bending is precisely the load that matters in a limb. The authors then built their limb from the best prepreg, but did not measure finished limbs made from the other two, so it is not known how much draw weight, arrow speed or vibration would change. It is a warning about the repeatability of the material, not a measurement on the bow, and the values can only be read from the paper's charts.

Also phrased as: "carbon limbs from different brands"; "carbon quality in limbs"; "prepreg for bow limbs"; "differences between identical limbs"

Evidence

• 2023
  For Equipment tests Published later

  Three unidirectional carbon prepregs from three Korean manufacturers, with Toray fibre and a stated resin content of 38 per cent, laid up in twelve plies and cured in an autoclave under the same conditions: in tension the three are similar, with the best modulus for the third; the second has the highest fibre volume fraction, the lowest measured resin content and the best bending and compression strength and modulus; under the electron microscope the machined surface of the first shows numerous pinholes, while those of the other two are clean. The values are in the paper's charts, not in a table, and the limb built afterwards uses only the second.

  Manufacture and Vibration-Damping Effect of Composites for Archery Carbon Fiber-Reinforced Polymer Limb with Glass Fiber-Reinforced Polymer Stabilizer · Won Wook Heo, Seung Kook An, Jeong Hyun Yeum, Seong Baek Yang, Sejin Choi

Status history

1. 2023 Reported The only test arrives: three unidirectional prepregs from different manufacturers, with the same fibre and the same stated resin content, laid up and cured the same way for recurve limbs. In tension they are alike, but one has more fibre, less resin and the best bending and compression values, and under the electron microscope the machined surface of another shows numerous pinholes. A test on equipment, a single one and on specimens, not finished limbs: reported.

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