The Standardization Office of Quebec mandated us to develop a test that could rate protective pads or leggings in terms of performance.
In the test, a chain saw was mounted on a horizontal axis about which it was allowed to rotate freely. A test consisted of letting the blade of this chain saw drop perpendicularly to the longitudinal axis of the legging that was mounted on a wood cylinder to simulate the leg of the worker. The legging was fixed on the specimen support in such a way that the textile threads could be pulled out by the chain so as to cause minimum interference with the protective mechanism of the textile. Wires on the legging and underneath the pad and an appropriate data acquisition system permitted measurement of the cut-through time and the chain saw speed.
The number of plies, the material thickness, and the chain saw speed were shown to change the cut-through time and stopping speed, which measures the maximum speed that the chain saw can run without actually cutting completely through the leggings.
For the first time, both performance criteria were measured with the same apparatus on the same type of leggings to confirm that these two different performance criteria were required to rate legging performance when no correction is made to the cut-through time for the free-fall time. The threshold stopping speed seems to be a preferable criterion.
The cut-through time was shown to be sensitive to the thickness of the material; the threshold stopping speed, to the strength of the assembly of fabric layers. Observations with a high-speed video camera (2000 frames/s) demonstrated the slowing of the chain by the fabrics, the stretching of the yarns up to the stitching on the perimeter of the pad, and the absence of bouncing during testing.