Composite Materials Design and Testing
Unlocking mystery with invariants

An innovative invariant-based approach developed makes trace of the plane stress stiffness matrix as the heart and soul of composite materials. It can put order in both stiffness and strength of composite laminates. Testing unidirectional [0] specimens should provide enough information for the prediction of the failure envelope of laminates. Then, laminates can be tested "as-built" and data compared to the predicted properties using a master stress-strain template, which greatly reduces the number of tests required. This method can be much more effective than the traditional building block approach. With fewer specimens to be tested, emphasis can be placed on the quality of laminates as reflected by the conversion of stiffness and strength from processing and its associated defects. Environmental effects such as hot-wet conditions can also be accounted for through their respective trace values. This new approach unlocks the mystery of composites design and opens up many opportunities in laminate design and manufacturing.