Failure analysis of the patch repaired E-glass chopped fiber strand mat/epoxy composites

The local repair of a damaged composite structure has the potential to restore the performance of the structure without replacing it. In this work, the tensile behavior of a patch repaired composite laminate is analyzed in detail using experimental and numerical studies. A 4-ply composite laminate is prepared by using E-glass chopped fiber mat as the reinforcement and Epoxy L12 as the matrix material. The damage is created in the laminate by drilling a hole of 8 mm at the center. The laminate is then repaired by adhesively bonding the same material as an external patch on both sides. Tensile tests have been carried out on healthy, damaged, and repaired specimens. It is found that the load carrying capacity is restored with the external patch repair. The longitudinal stiffness and the load carrying capacity are restored by 75% and 90%, respectively. A three-dimensional finite element modeling of the tensile tests has been carried out to analyze the stress distribution in all three specimens. A brief literature review is also presented about the mathematical models used to estimate mechanical properties of the chopped fiber strand mats. In this work, the elastic properties of the random fiber chopped strand mat are estimated using the modified rule of mixtures. From the results of the numerical study, it is found that the stress concentration around the damage is reduced by 70% with the patch repair. The present study is mainly useful for maintenance engineers.

Automated summary

The study demonstrates that external patch repair can effectively restore the load carrying capacity and longitudinal stiffness of a composite structure. The research is beneficial for maintenance engineers.