Material, Manufacturing, and Service Defects

In general, regardless of the part being manufactured, there will be some level of flaws and damage that is considered acceptable. Anything above that level is a defect, and must be substantiated, repaired, reworked, or replaced. This chapter discusses the ways to reduce defects in composite structure. Cosmetic defects can be defined as defects that only cause a change in appearance without detrimental effect on the load-carrying capacity of the composite part. Many of the defects discussed in the chapter can result from events occurring during service of a structure and thus must be considered within the overall strategy of design and operation of a composite structure. Bearing damage refers to damage resulting from bearing loads in a composite structure loaded parallel to the plan of the structure. Bearing damage is a mixed-mode failure scenario that encompasses fiber micro-buckling, matrix cracking, delamination, and out-of-plane shear failures.