Session: 04-10-01: Impact, Damage and Fracture of Composite Structures

Paper Number: 70354

Start Time: Monday, 05:30 PM

70354 - Analyzing Core Failure in Composite Sandwich Structures Using a Non-Local Anisotropic Damage Approach 

Sandwich structures have been widely adopted in structural designs to reduce overall structural weights while maintaining sufficient in plane and flexural stiffness. A sandwich structure often consists of two skin layers and a core layer in between. Fiber reinforced laminates are commonly adopted for skin layer design. Depending on the industrial applications, different type of core materials may be used (e.g., honeycomb for an aircraft design, foam core or balsa wood for a wind turbine blade design). and the material properties of a core material are generally different between in-plane and extrusion directions. Due to such unique combination of materials, various failure modes could occur within a sandwich structure upon loading, and core failure is one of the major and earliest failure modes. Although core failure itself would not lead to the catastrophic failure directly, the further progression of failure might lead to the subsequent separation between core and skin layer, and thus introduce local instability that could result in the final collapse of a sandwich structure. As a result, to analyze core failure properly, both the initiation and progression of the failure need to be investigated. However, to authors’ best knowledge, there is no universally accepted approach that could evaluate the whole core failure process properly.  

The objective of this work is to present an efficient computational approach that would help structural designer or researchers better evaluate the core failure in a sandwich structure. In the present work, a Continuum Damage Mechanics (CDM) approach has been adopted numerically to study core failure in a sandwich structure. The computational framework is based on the anisotropic damage model proposed in [1], where a quadratic damage degradation functions was developed to account for the anisotropic elastic response of the material and a gradient enhance formulation was derived to avoid singularities caused by local strain softening and thus realize a mesh-independent solution. To evaluate the applicability of the proposed approach in core failure analysis, several case studies were conduct using sandwich structures of different configurations such as core thickness and core tapering ratio under various loading conditions. For each case, the initiation and progression of core failure were captured and discussed in detail. Finally, based on the observations during the study, recommendations were suggested on the future use of proposed approach to analyze the core failure in a composite sandwich structure.

[1] Yin, B., Zreid, I., Lin, G., Bhashyam, G., & Kaliske, M. (2020). An anisotropic damage formulation for composite materials based on a gradient-enhanced approach: Formulation and implementation at small strain. International Journal of Solids and Structures, 202, 631-645

Presenting Author: Linqi Zhuang Ansys, Inc

Authors:

Linqi Zhuang Ansys, Inc.
Ali Najafi Ansys, Inc.