Investigation of Delamination Suppression in Highly Tapered Composite Laminates

Date

2023-12

Author

Ergin, Fırat

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The presence of ply termination locations makes tapered composite laminates susceptible to delamination, thereby reducing the overall structural performance. The primary objective of this study is to propose a novel design alternative for highly tapered laminates with the aim of suppressing delamination onset. In situ experiments on dropped ply specimens are conducted to identify the failure mechanisms within ply drop-off regions. Different delamination modes and their dynamic progression in dropped ply specimens are effectively captured through experimental procedures. Material characterization tests for a Glass Fiber Reinforced Polymer (GFRP) and epoxy resin system are conducted to obtain the mechanical properties essential for the development of finite element models. Cohesive zone modeling technique is employed in FE models to predict delamination. Effects of through-thickness compression enhancement of shear properties and modeling details around the resin pocket are also investigated numerically. The finite element models for single-stage ply drop-off region effectively replicated the delamination onset loads and locations observed in the experimental studies. A parametric taper angle study on a single-stage ply drop-off region revealed that an increase in the taper angle significantly decreases the delamination onset load at the beginning of the thin section of the tapered laminate. Building on this finding, the study introduces the variable taper angle design concept. This design aims to delay the thin section delamination in highly tapered laminates by providing a gradual transition in the taper region. The finite element results of the proposed design concept demonstrated that a substantial improvement of nearly 80% on delamination onset load can be achieved through the proper selection of the taper geometry.

Subject Keywords

Tapered Laminates, Delamination Suppression, Cohesive Zone Method, Finite Element Method

URI

https://hdl.handle.net/11511/107658

Collections

Graduate School of Natural and Applied Sciences, Thesis