A Comparison of Requirements and Test Methodologies for a Variety of Impact Absorbing Materials

Several years ago I was hiking on Mt. Rainier. I had just crossed a rock field where I had previously stowed my ice axe and gloves in my pack when I came to a nice smooth snow field. I noticed the snow field was fairly steep and also that there was a tree line about 150 yards down slope. However, I was relieved to be getting to smoother hiking and stepped right out. The first step was just fine and then suddenly my world changed. My foot slipped, twisting me around and depositing me on my back. I found myself hurtling toward the tree line head first and accelerating rapidly. At that point I realized that Abraham Maslow had it all wrong. My most basic need wasn’t my next breath, in fact, I don’t think I was breathing at all. The only thing on my mind was deceleration! Or at the least, some way to LIMIT an IMPACT with a tree trunk. As luck would have it, I managed to flip over and dig into the snow with my feet, knees, elbows and fingers and come to a safe albeit bloody stop. The point of this story is that stopping a rapidly moving object can be a life or death matter. All too often, the question of how to stop an object safely is given little attention until late in the design phase of many projects. For example, how often does a guy showing off his new car point out the brakes? Fortunately for me in my hiking experience I had practiced arresting a fall. While I had always practiced arrests with an ice axe, at least I had discussed what to do if I lost the axe. I am still alive today only because my coach and I anticipated the possibility of an accidental fall.