The devil is in the detail: Understanding how composite materials fail

Picture Credit: by Wikipedia

Composite materials are considered as next generation materials, due its tailor-made unique properties. Composite materials are made by combining two or more materials that are different in physical and/or chemical characteristics. The material thus created has properties that are superior to their constituents. Composites are usually made in thin layers and then multiple layers are permanently bonded together by means of pressure, heat, adhesion, welding or a combination some of these.

Picture Credit: by Wikipedia

Because of advantages like ease of molding and shaping, high corrosion resistance, high strength and stiffness in relation to weight etc, composites and their laminates are the materials of choice in several modern industries such as aerospace and marine. However, while their physical and other characters are well known and predictable, much needs yet to be learned about how various laminate composites behave when they fail or are damaged.

Picture Credit: by Wikipedia

First, even after they are combined, the component materials remain distinct and separate within the composite unlike alloys. Therefore, interactions between the component at the minutest level and under different conditions and loads play a part in how the composite behaves. Since any number of different components can be chosen to create a composite, the behavior of each component individually as well as when interacting with each of the other components have to be studied.

In the case of laminates it becomes even more complicated because the dynamics of the interactions between the layers also have to be taken into consideration. Especially, when studying the process of damage, since the process of damage in any material originates at a smaller scale than visible to the naked eye. Similarly, damage in laminated composites often originates at microscale i.e. at fiber/matrix scale. There are various damage mechanisms simultaneously activated during the failure process of the laminated composites. Each component in the composite laminate fails in a different manner.

Picture Credit: by Wikipedia

A lot of work has already been done in studying damage mechanisms at the macro-scale i.e. at the scale of lamina. But it is important to study micro-scale active damage mechanisms like fiber breakage, matrix cracking and fiber-matrix debonding which lead to failure of the lamina. At the IITB-Monash Research Academy in Mumbai, Research Scholar Ganesh Soni has been addressing this lacuna in the existing body of knowledge. The aim of his research is to capture material response and various damage mechanisms acting simultaneously at micro-scale via the finite element method. Ganesh has fashioned a path-breaking new model for the study of damage in composite laminates using multiscale modeling approach.

Ganesh has proposed a three dimensional multi-layer multi-fiber representative volume element (M2RVE) to capture all likely inter-laminar and intra-laminar damage mechanisms, viz., fiber breakage, fiber-matrix debonding, matrix cracking and delamination. It is a better geometrical representation of the laminate as compared much simplified models suggested by other researcher’s in the past. In this model the effects of geometry and spatial distribution of the fibers, on the onset and propagation of the matrix damage and fiber-matrix debonding can be captured explicitly. It is also possible to capture all likely intra-ply and inter-ply damage mechanisms, simultaneously.

Picture Credit: by Ana Ulin, Fliker

Ganesh has also proposed a new micro-macro approach to address the limitations of the use of periodic boundary conditions to capture damage in region of stress singularity (High stress zone). In this method, the microstructural details are included in a small region of interest in the structure and the rest is modeled as a homogeneous continuum. The solution to the microstructural fields is then obtained on solving the two different domains, simultaneously. This method accurately predicts local stress fields in stress concentration regions and is computationally efficient as compared with the solution of a detailed microstructural model.

Says Ganesh, “It is exciting to understand how damage initiates, propagates and finally takes a form of visible form in composite laminates”.

The IITB-Monash Research Academy is a Joint Venture between the IIT Bombay, India and Monash University, Australia. Opened in 2008, the IITB-Monash Research Academy operates a graduate research program located in Mumbai that aims at enhancing research collaborations between Australia and India. Students study for a dually-badged PhD from both institutions, and spend time during their research in both India and Australia.

Research scholar: Ganesh Soni

Project title: Novel Multiscale Modeling Schemes for Damage Evolution in Composite Laminates

Supervisors: Ramesh Singh, Mira Mitra, Wenyi Yan, Brian G. Falzon

Contact details: ganeshsoni123@gmail.com

Contact research@iitbmonash.org for more information on this, and other projects.