ROBUST DESIGN – AN EVOLUTION FOR IMPERFECTION INSENSITIVE COMPOSITE STRUCTURES

Robust design is a design philosophy that aims to ensure that a structure will be tolerant to un-known variations and imperfections in the design. While safety factors do provide a tolerance to variability and uncertainty in the analysis, they do not offer any indication of the sensitivity of a de-sign due to these uncertainty factors. This is an important consideration as highly optimised critical structures are required to survive unexpected loading and operating conditions. In many ways, robust design appears to be similar to damage tolerant design but there are distinct differences between the design philosophies. While there is a wealth of knowledge and applications relating to damage tolerant design, robust design is still not fully understood in structural design. A stiffened composite panel has been analysed for damage tolerance and robustness properties. Damage tolerance has been studied under experimentation with the panel subjected to impact damage while robustness has been assessed using finite elements and a Robust Index. The index is used to quantify the robustness of the structure and an investigation has been undertaken to highlight the differences between the two design philosophies. This investigation has found that structures that are robust are also damage tolerant but the reverse may not be true