A review on manufacturing defects and their detection of fiber reinforced resin matrix composites

Fiber reinforced resin matrix composites are more and more widely used in aerospace and automobile manufacturing industries. However, the probability of manufacturing defects in composites is very high due to the complex physical and chemical properties of component materials and molding processes. Therefore, the research on the manufacturing defects and their detection of composites becomes important in evaluating the quality of composites. First, the formation mechanism of residual stresses, void defects and resin-rich defects in the matrix of composites are summarized. Especially, the curing of thermosetting resin and thermoplastic resin, the resin infiltration process in hot pressing, resin transfer molding and 3D printing, and resin-rich defects in molding process are described in this article. Second, the forming mechanism of fiber reinforcement defects such as fiber wrinkle and waviness in composites is introduced, and the influence of such defects on the bending and compression properties of composites is analyzed, which shows that fiber misalignment defects will seriously reduce the modulus, strength and stability of the supporting structures. Third, formation mechanism, damage causes and optimization methods of interfacial defects such as delamination and debonding in the interface between reinforcements and matrix are elaborated. Fourth, machining defects such as drilling and cutting defects are revealed. The main manifestations are delamination, tearing, and burrs, which will seriously affect the strength and reliability of the connection between components. Finally, the non-contact detection of defects in composites are shown in the article. Different detection methods can be used to measure defects of different scales to predict composite damage and life in advance. This review analyzes manufacturing defects in laminated, woven, braided, and additive manufactured composites, and summarizes common defect detection methods, also presents an outlook for composite manufacturing.