 We all rely daily on the structural integrity of man-made objects. From the supporting structure of the building you are in now, to the mode of transportation that brought you there in the first place. Your safety constantly relies on something not breaking. However, no structure is indestructible. Time, repeated use, the environment and even the occasional mishap all take their toll on a structure bringing it closer and closer to failure. Not the most comforting thought to have when flying on an airplane, particularly when you consider the amount of effort spent to optimize its design in terms of weight. So how do we deal with this sobering reality in practice? In the simplest terms, we design aircraft structures to fail, but in a progressive and manageable way. A friendlier wording to use is to say that we design structures as damage tolerant. We accept that damages can occur, whether it's causes predictable or not, and design the structure to tolerate that damage and its potential growth over time so that we can find it and repair it before it becomes catastrophic. Applying the damage tolerant methodology relies heavily on our understanding of progressive failure modes. The time between a damage exceeding a level that we can detect until it reaches a critical level defines the window of opportunity to detect problems through inspections. Ideally, we would like to have as large a window as possible to detect damages and make potential damages as easy to inspect for as we can. Both of these can be achieved through careful design. This approach to safety has been very successful in the aerospace industry, but we face an ever-increasing challenge. The structures of today are relatively simple, but the structures of tomorrow are becoming increasingly complex due to new technologies such as additive manufacturing, also known as 3D printing. These technologies enable structures that are more bio-inspired, more environmentally conscious in their design, more intelligent with embedded sensors, and made with new, complex material systems such as self-healing materials. We need to understand the implications of each of these complexities on the progressive failure behavior of future structures. In order to maintain the level of safety and confidence we have come to expect in modern structures. Although understanding these added complexities is necessary in order to achieve the current level of safety we all enjoy today, my research vision goes a step further. I believe that not only can we make structures as safe as today, but we can enhance their safety through this understanding. For example, by understanding the complex cellular structures of citrus fruits, we can tailor complex graded 3D printed structures to absorb energy in a way that improves the survivability of a crash or impact scenario. Other safety benefits can also be envisioned. What if we could improve the damage tolerance of a 3D printed part design simply by printing it in a different orientation? What if we could design a highly redundant and damaged tolerance structure inspired by the complexity observed in nature? In my research, I strive to generate this enabling understanding to ensure that the aircraft of tomorrow exceed the unprecedented level of safety we enjoy today.