Self-Diagnosis of Damage Criticality of Fibrous Composites Based on Multifunctional Characteristics

This STTR project is an in-situ/real-time aerospace composite structural self diagnosis (SSD) and structural health monioring (SHM) system/technique development with application of multifunctional characteristics of aerospace composite weapon systemstructures made of graphite-epoxy composite materials and carbon-carbon composite materials. Composite SSD and SHM are accomplished by measuring electrical resistance changes in the carbon-fiber composites that are as desgined and manufactured.Delamination and fiber breakage along with disbond are major forms of composite structural damage. Delamination causes composite laminate separation in a micropic scale, and fiber breakage causes discontinuity of carbon fibers. The delamination and fiberbreakage increase electrical resistance in thickness and longitudinal primary loading directions of a composite lamainate, respectively. The electrical resistivity (normalized electrical resistance)change provides pertinent information on compositestructural damage detection. The proof of concept (POC) demonstration of an electrical resistivity-based damage criticality assessment technology (for phase I) and its full-scale development (FSD) tasks (for phase II) are proposed for aerospace compositeweapon systems SSD and SHM under this STTR project. The proposed technology does not require specially made third-party sensors, e.g., PZT, fiber-optic, MEMS, etc. Consequently, it aviods the parasitic effects caused by the sensors (i.e., fatigueproperties degradation due to foreign object materials embeddment), and eliminates the added costs for the sensors. The proposed eletrical resistivity-based SSD and SHM system/technique can also be applicable to already fielded (currently in-service)composite weapon system structures as well as new weapon system structures to be designed and manufactured. Hence, it is cost-effective and performance-efficient. When this technology is fully developed, it can not only be applied to military weaponsystems but also to commercial aerospace vehicles and civil infrasturctures.