Computational Prediction of Mechanical Performance of Particulate-Reinforced Al Metal-Matrix Composites (MMCs) using a XFEM Approach Emily A. Gerstein and Chang-Soo Kim, Ph.D. Material Science and Engineering Department, CEAS, UWM 2017 Spring CEAS Undergraduate Poster Competition

Background Information Composite materials can offer an array of attractive properties for automotive and aerospace applications, including weight savings and increased critical load bearing capabilities. Silicon carbide (SiC) reinforced aluminum (Al) metal-matrix composites (MMCs) present a high stiffness-to-weight ratio, enhanced resistance to high cycle fatigue accompanied by a high threshold for fatigue cracking, improved wear resistance, a reduced coefficient of thermal expansion (CTE), and a high thermal conductivity. The extended finite element method (XFEM) is an up-and-coming method for computationally predicting damage evolutions resulting from crack propagation within advanced composites. Fig. 1: Increased use of composites in aerospace applications1. Fig. 2: Projected use of composites in consumer vehicles2.

Experimental Characterization Data Property Considerations Research Objectives and Approach Development of a 2D XFEM approach for modeling damage evolution and crack propagation within particle reinforced Al-SiC MMCs. Prediction of stress-strain data and MMC failure mechanisms with various microstructural features and material properties such as particle arrangement, reinforcement volume fractions, and matrix critical strain energy release rates (G). This particular work utilizes 10, 20 and 30 vol % SiC in regular and random arrangements with variations in Al60601 G. Modeling Framework Experimental Characterization Data XFEM Shape Considerations Adaptive Remeshing scheme Property Considerations GIC Inclusion Size Vol % SiC Arrangement

Computational Methods SiC Al6061 Young’s Modulus (GPa) 350 80 Maximum Principle Stress (MPa) 205 Critical Energy Release Rate (J/m2) 5.26 1, 2, 5, 15, 30 Poisson’s Ratio 0.22 0.33 Table 1: XFEM composite material properties. 𝒖= 𝐼=1 𝑁 𝑁 𝐼 (𝑥) 𝒖 𝐼 +𝐻 𝑥 𝒂 𝐼 + 𝛼=1 4 𝐹 𝛼 (𝑥) 𝒃 𝐼 𝛼 XFEM Constitutive Relationship Study Assumptions and Approaches: Representative volume element (RVE) can represent the actual mechanical performance of composites. Therefore, Computation domains are representative of long-range material properties. Material properties are homogeneous in each phase (SiC reinforcement particles and Al metal matrix) and the two phases form coherent interfaces. The shape of reinforcement particles is spherical (circular in 2D).

Regular Particle Arrangement: Increasing Volume Fraction Regular, 10 vol % SiC, G = 30 J/m2 Initial 1.5% Strain 3% Strain Fig. 3: Stress-strain relationships in Al-SiC MMCs with regular particle distribution and varying particle volume fractions. Initial 1% Strain 2% Strain Regular, 20 vol % SiC, G = 30 J/m2

Random Particle Arrangement: Increasing Volume Fraction Fig. 4: Resulting stress-strain relationships in Al-Sic MMCs with random particle distribution with varying volume fraction. Initial 0.55% Strain 1.1% Strain Random 10 vol % SiC G = 30 J/m2

Regular Particle Arrangement: Increasing Fracture Energy Regular, 10 vol % SiC, G = 30 J/m2 Initial 1.5% Strain 3% Strain Fig. 5: Variation in stress-strain relationships with Al critical energy release rate in regularly distributed matrices with 10 vol % SiC. Initial 0.8% Strain 1.65% Strain Regular, 10 vol % SiC, G = 2 J/m2

Summary and Acknowledgements More regular arrangements of SiC particles within an Al matrix may allow for a stronger and more ductile materials. Yield and ultimate tensile strengths generally increase with increasing amount of reinforcement volume fractions at the expense of material ductility. These results demonstrate that XFEM can offer a viable means by which tensile data and information about the failure mechanisms of advanced composites, particularly those resulting from the propagation of flaws, may be garnered. Weak matrices with lower critical energy release rates are more prone to fracture at lower stress concentrations and under lower amounts of strain. This work was supported through the UWM College of Engineering and Applied Sciences Engineering Excellence Scholarship Program. Acknowledgements References Trilaksono, A., Waranabe, N., Kondo, A. et. al. (2014). Automatic damage detection and monitoring of a stitch laminate system using a fiber bragg grating strain sensor. Open Journal of Composite Materials, 4: 47-60. McConnell, V.P. (2011). Not just another road trip. Reinforced Plastics, 55(5): 3-54.