Hygrothermal aging effects on the mechanical behavior of scarf-repaired composite laminates

ABSTRACT

Adhesively bonded techniques have been widely used to joint or repair composite components in aircraft structures, which are inevitably subjected to various environmental conditions in service. Aiming to investigate the effect of hygrothermal aging on scarf-repaired composite structures, bulk adhesive specimens and scarf-repaired composite laminates of three different laminate thicknesses were tested before and after hygrothermal aging in this paper. Experimental results indicate that the strength reduction of scarf-repaired composite laminates after aging is less evident than that of bulk adhesive. For scarf-repaired composite laminates, a linear relation is found between the strength reduction and their moisture contents. Visual inspection and microscopic observation were performed to investigate the damage mechanism. In addition, a finite-element model based on continuum damage model and a degraded bilinear traction–separation cohesive zone model considering hygrothermal aging degradation was established. The predicted strength and failure modes achieve good agreement with experimental results.

KEYWORDS:

• Composites
• scarf repair
• hygrothermal aging
• degraded CZM

Acknowledgements

The authors thank Mr. Chengzhe Zou at The Ohio State University for the writing polish works.

Additional information

Funding

This work was supported by the Natural Science Basic Research Plan in Shaanxi Province of China [grant number 2017JM1027] and the Fundamental Research Funds for the Central Universities in China [grant number 3102017HQZZ002], [grant number 3102017jghk02001].