Simulation of crack propagation in mesh and composite materials

Composite materials and meta materials (materials with mesh structure, hollow structure) are being researched and widely applied in modern industry. Due to the complex structure and manufacturing process of the material, it is easy for defects to arise during the production of the material. The appearance of cracks will significantly reduce the hardness and strength, as well as to the material properties; especially during work, cracks may continue to develop. Therefore, it is necessary to study the effects of cracks as well as crack propagation in composite and meta-materials. From the above practical requirements, Dr. Pham Hong Cong and the research team of the Center for Informatics and Computation have conducted the project: "Simulation of crack propagation in elastic gradient materials, application in mesh and composite materials" (Code: VAST01. 02/21-22). The topic was rated A by the Acceptance Council at Vietnam Academy of Science and Technology.

Today, microstructures, structures made of anisotropic materials, are being widely applied in technical life such as medicine (bones, joints), nuclear energy (septums, reactors), defense industry (missile engines), shipbuilding (propellers, internal combustion engines), and surveying (sensors). For these structures, even during the manufacturing process and during the working process, micro-cracking defects (which are cracks that form and can spread, can become cracks after a period of time) may appear, and these cracks will develop and reduce the workability of the structure. Therefore, studying the mechanical behavior of structures with cracks has scientific and practical significance, helping scientists understand the crack development characteristics for each type of material and structure, from It predicts the possibility of crack growth, as well as proposes reasonable reinforcement measures to control the crack in the most beneficial direction.

The research team used the Phase-field theory combined with the finite element method to analyze the effect of the crack and simulate the propagation of the crack. This method is an effective tool to solve cracked structures, by using a continuous variable, turning the cracked domain (discrete domain) into a continuous domain.

One of the typical examples of mesh and composite materials studied and investigated in this study is auxetic materials with negative Poisson coefficients.

As the most studied array of mechanical metamaterials, auxetic materials are known for their unusual behavior during deformation. More specifically, under the action of axial compression, ordinary materials expand in a direction orthogonal to the applied load. In contrast, auxetic materials will tend to shrink, as shown in Figure 1.


Figure 1. Material behavior under tensile and compressive loads. (a) Ordinary materials; (b) auxetic materials

The model of the layered composite sheet is shown in Figure 2, in which the sheet consists of 3 layers of material, cracks appear in the middle layer. From these calculation results, it can be seen that the individual vibration patterns of the composite plate with cracks and without cracks are not much different in shape, but the crack has an influence on the natural frequency of vibration.

Figure 2. Model of composite panels made of composite materials

The topic uses phase-field theory combined with plate theory to establish basic equations, finite element method to study the propagation process of cracks in elastic gradient materials. Thereby, a new approach has been created in studying the mechanical behavior of mesh and composite materials with static and dynamic cracks.

Understanding crack propagation in mesh and composite materials directly gives engineers new safety parameters in designing products with high safety and material savings. Based on crack propagation in mesh and composite materials, design engineers offer reinforcement solutions for defective products to maintain product life at an economical cost.

Figure 3a. Experimental propagation crack results Figure 3b. Result of crack propagation according to calculation

The new contributions of the research team are the use of phase-field theory combined with the finite element method to describe the crack propagation process in micro-sized structures, taking into account the effect of size response. Application of phase-field theory and finite element method to simulate the mechanical response of structures made of mesh, composite and crack materials. Investigate the influence of some parameters on the mechanical response of structures made of different materials with cracks.

The research results of the topic were published in 05 scientific works, of which 3 articles were published in prestigious international journals (Q1), 01 article was accepted for publication in VAST2 and 01 article published in a domestic magazine.


Translated by Quoc Khanh
Link to Vietnamese version

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