Mechanical properties such as the strength and stiffness of a material must be known to design an optimized structural component from that material. While measured mechanical properties are well established for common metal alloys, composite materials can present unique challenges due to their limited standardization and wide range of material and process variables. This lack of published material properties makes designing structural composite parts challenging. Analysis tools such as Finite Element Analysis (FEA) can help guide a design, but they rely on material property inputs that must be accurate in order to achieve reliable results. The best way to obtain accurate numbers for these input variables is through physical testing on representative composite test samples. Without accurate inputs, analysis results may overestimate the strength and stiffness of a composite material, leading to structural failures and safety risks. Large safety margins must be added to a design to account for unrefined quantification of material properties. This adds weight, ultimately defeating one of the main reasons composite materials are selected in the first place. Thus, there really is no way to completely eliminate physical testing from the design process of an optimized composite structure. Specific methods used to measure mechanical properties of composite materials and validate composite structures are discussed in the following sections.