| Description |
This thesis describes experimental and numerical research concerning transverse fracture in fiber reinforced polymer matrix composites (PMCs). Transverse fracture is one of the most common and initial types of damage seen in PMCs and is considered a precursor to other more severe damage modes. Understanding how transverse cracks propagate at the microscale and how to model transverse fracture at the ply-level in PMCs remain topics of ongoing research and motivate the work in this thesis. The first part of this thesis describes an experimental effort to image and analyze the evolution of microscale transverse tensile fracture in tape-laminate carbon/epoxy composites under far-field mode-I loading. A transverse double cantilever beam (TDCB) specimen is developed with fibers surrounding the crack-tip oriented in the transverse direction. TDCB specimens are wedge-loaded with a custom micromechanical test fixture and optically monitored at both the micro- and macroscale simultaneously. After testing, micro- and macroscale images are analyzed to determine relationships between far-field loading and microscale crack growth. The obtainable datasets from the proposed experiment enable creation and direct validation of finite element (FE) simulations of transverse tensile cracking in PMCs at the microscale and provide impetus for further model development. The second part of this thesis presents a generalized three-dimensional (3D) implementation of the floating node method (FNM). The FNM is a numerical method to iv discretely represent mesh-independent discontinuities in a material. The algorithm developed herein permits modeling of 3D angled transverse-cracks in PMCs in a FE framework. When elements are split to represent angled cracks with the FNM, the proposed scheme handles the complex partitioning and integration of the resulting polyhedron-shaped solid and cohesive-zone elements. A salient feature of the proposed algorithm is its ability to simulate growth and interaction of transverse cracks and delaminations in PMCs. The proposed algorithm is verified against a series of single-element tests with a wide range of crack angles and interaction combinations to ensure its robustness. |
