In Chapter 1 we discussed the durability assessment of composite structures, theoverall goal for the subject of this book. As outlined there in Figure 1.1, themechanisms of damage and their effects on deformational response constitute themain thrust of the field of damage mechanics, which is at the core of durabilityassessment. After discussing the physical nature of damage observedexperimentally in Chapter 3, the next two chapters treated the two mainapproaches in damage mechanics – micro-damage mechanics (MIDM) andmacro-damage mechanics (MADM), both aimed at predicting deformational responseat fixed damage. Damage evolution was treated in Chapter 6, while Chapter 7 wasdevoted to fatigue, a subject that requires special attention due to theconceptual difficulties it poses.

In closing the book we wish in this chapter to review what has been achieved andwhat directions the field of damage and failure of composite materials shouldpursue to further advance toward durability assessment and beyond.

Computational structural analysis

Obviously, complex structural geometries require computational structuralanalysis. The analytical modeling of damage initiation and evolution, and itseffects on deformational response of composite laminates, discussed in previouschapters, were developed for idealized simple cases. Direct application of thesemodels is limited to structures with simple geometry and loading conditions. Forcomplex geometries, such as an airplane wing or a wind turbine blade, usuallysubjected to multi-axial mechanical loads, and possibly combined with thermaland moisture environments as well as manufacturing-induced residual stresses,computational approaches are inevitable. In industry, one often uses commercialsoftware, e.g., ANSYS, ABAQUS, and NASTRAN, and the obvious need is to integratedamage and failure analyses into these codes. Efforts have been made to attemptsome simple test cases where FE analysis of composites is combined with damageusing failure criteria [1]. A series of World Wide Failure Exercises (WWFE)[2–4] have been conducted to compare several composite failure models withexperimental data and provide guidance for their usage in composite design.