Date of Award
2025
Document Type
Open Access Dissertation
Degree Name
Doctor of Philosophy in Mechanical Engineering-Engineering Mechanics (PhD)
Administrative Home Department
Department of Mechanical and Aerospace Engineering
Advisor 1
Trisha Sain
Committee Member 1
Siva Nadimpalli
Committee Member 2
Pavana Prabhakar
Committee Member 3
Parisa Pour Shahid Saeed Abadi
Abstract
Fiber-reinforced polymer composites (FRPCs) are widely used in aerospace, automotive, and civil engineering due to their high specific strength, stiffness, and durability. However, their anisotropic and heterogeneous nature makes fracture prediction challenging, with damage modes classified as intralaminar failure (matrix cracking, fiber breakage, fiber-matrix debonding) and interlaminar delamination. Delamination, driven by weak through-thickness strength and high interlaminar stresses, is a predominant failure mechanism in FRPCs. While cohesive zone models (CZMs) are commonly used for delamination, they are computationally expensive and inefficient for capturing intralaminar fractures where crack paths are unknown. To address this, we developed a unified phase field-based cohesive zone model (PF-CZM) capable of predicting both intralaminar and interlaminar fractures while quantifying mode-I ($G_{Ic}$) and mode-II ($G_{IIc}$) fracture energies. The model was validated against experimental data, demonstrating its accuracy in capturing delamination and matrix cracking. However, failure in FRPCs involves complex interactions between these damage modes, particularly in multi-layered laminates with varying fiber orientations, where mechanical property mismatches and interfacial decohesion create displacement field discontinuities. To overcome this, we developed an anisotropic interface-regularized phase field approach in 2D, incorporating a traction-separation-based interfacial constitutive model to capture bulk-interface fracture interactions. This framework effectively modeled matrix crack initiation, propagation, and delamination, where traditional models struggled. To account for out-of-plane deformations and crack twisting in off-axis laminates, we extended this approach to 3D, enabling accurate predictions of delamination and intralaminar-interlaminar interactions in FRPC laminates under complex loading. Finally, we advanced our model by incorporating thermomechanical coupling and the viscoelastic behavior of the polymer matrix. This enhanced framework captures time-dependent deformation, thermal effects, and anisotropic fracture evolution in CFRPs, considering temperature-displacement-driven damage, viscoelastic dissipation, and crack propagation. Our work provides a comprehensive approach to fracture modeling in FRPCs, offering critical insights into failure mechanisms and contributing to the design of more durable, high-performance composite structures.
Recommended Citation
Kumar, Akash, "PHASE-FIELD METHOD OF FRACTURE IN FIBER-REINFORCED POLYMER COMPOSITES: THEORY, MODELING, AND VALIDATION", Open Access Dissertation, Michigan Technological University, 2025.