Development of a Mesoscale Finite Element Constitutive Model for Fiber Kinking

Abstract

A mesoscale finite element material model is proposed to analyze structures that fail by the fiber kinking damage mode. To evaluate the assumptions of the mesoscale model, the results were compared with those of a high-fidelity micromechanical model. A direct comparison between the two models shows remarkable correlation, indicating that the key features of the fiber kinking phenomenon are appropriately accounted for in the mesoscale model. The mesoscale model is applied to structural analysis cases to demonstrate the capabilities of the model. A verification study is conducted with an unnotched compression specimen and preliminary validation is demonstrated with a notched compression specimen. The results show that the model is successful at representing the kinematics of fiber kinking while at the same time highlighting the need for further verification and validation.

A study on the longitudinal compression strength of fibre reinforced composites under uniaxial and off-axis loads using cross-ply laminate specimens

“…In an analogous way, is obtained from the very same constitutive law ( Both models were calibrated with the average uniaxial compression strength and shear stress-strain behaviour from [14,15] and gave an initial misalignment angle of 1.85°, which falls within typical expected values and matches the analytical solution for the uniaxial compression case as described in [26]. With the proposed modification, the solution remains unchanged for the pure compression case but, for off-axis compression cases, there are some noticeable improvements.…”

Validation of a Mesoscale Fiber Kinking Model through Test and Analysis of Double Edge Notch Compression Specimens

“…A constitutive model based on FKT (assuming = 0) was recently proposed and implemented into the NASA continuum damage mechanics code for progressive damage analysis, CompDam [5,9]. This model is further developed by adding consideration for fiber failure in the post-peak portion of the constitutive response.…”

“…The fiber-kinking theory introduced by Budiansky offers a physics-based model for kink band initiation and propagation [3,4]. Recently, a model based on this fiber-kinking theory was proposed and implemented into the NASA continuum damage mechanics code for PDA, CompDam [5]. A mesoscale model was formulated with consideration for the kinematics of fiber kinking, including shear instability and a post-peak non-zero residual stress.…”

“…The model was verified through detailed comparisons with a highfidelity micromechanical model and an analysis of an unnotched unidirectional coupon subjected to compression. One factor that was not explored in reference [5] is the response under large deformations, after kink band initiation. Furthermore, only limited validation of the model was conducted.…”

“…First, the experimental procedure utilized for testing a series of geometrically scaled DENC specimens, inspired by [6], is summarized. Next, the CompDam fiber-kinking model described in [5] is summarized, and a simple extension is introduced to consider hardening in the constitutive response after a kink band has formed. Finally, the test and analysis results are presented and discussed.…”