Structural integrity and the implementation of engineering composite materials

Predicting precisely where a crack will develop in a material under stress and exactly when catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large-scale engineering structures. Where human life depends upon engineering ingenuity, the burden of testing to prove a ‘fracture-safe design’ is immense. When human life depends upon structural integrity as an essential design requirement, it takes ten thousand material test coupons per composite laminate configuration to evaluate an airframe plus loading to ultimate failure tails, wing boxes and fuselages to achieve a commercial aircraft airworthiness certification. Fitness considerations for long-life implementation of engineering composites include understanding phenomena such as impact, fatigue, creep and stress corrosion cracking that affect reliability, durability of structure and life expectancy. Structural integrity (SI) analysis treats the design, the materials used, and figures out how best components and parts can be joined. Furthermore, SI takes into account service duty. However, there are conflicting aims in the complete design process of designing simultaneously for high efficiency and safety assurance throughout an economically viable lifetime with an acceptable level of risk.