Failure Prediction of Notched Composites Using Multiscale Approach

Abstract

This paper presents multiscale-based failure criteria to predict the failure of polymer composites with any shape of defect. The multiscale technique consists of bi-directional processes called upscaling and downscaling processes to link two different length scales. One is the microscale at the fiber and matrix material level, and the other is the macroscale at the homogenized composite material level. Failure criteria are applied to the microscale level such as micro-stresses and/or micro-strains occurring at the fiber and matrix material level. Recently proposed unified failure criteria are applied to the micro-stresses and/or micro-strains to predict failure at a notch. The new failure criteria have two parts, and they can be applied to any shape of defect. One is the stress or strain condition, and the other is the stress or strain gradient condition. For failure to occur, both conditions must be satisfied simultaneously. The failure criteria provide not only failure locations but also directions of failure propagation.

Predicting Failure of Additively Manufactured Specimens with Holes

“…The recently proposed unified failure criterion consists of two parts, both of which must be satisfied for failure to occur [ 18 , 19 , 20 ]. The failure criterion can be applied to specimens regardless of whether they have a defect, e.g., a crack or a hole.…”

“…Both failures compared very well with each other regardless of the hole size and printing angle. That is, the failure criterion [ 18 , 19 , 20 ] predicted applied failure stresses successfully for the PLA specimens.…”

“…Different failure criteria have proposed different ways to determine the critical distances. More recently, a new unified failure criterion was developed [ 18 , 19 , 20 ]. The previous study demonstrated that the new failure criterion applies to brittle materials regardless of whether they contain a defect or not.…”

“…The next section describes the preparation of 3D printed specimens and the design of combined loaded test specimens. Subsequent sections describe the material testing and an investigation of the failure criteria [ 18 , 19 , 20 ], followed by computational modeling results. Lastly, predictions of failure are made using the new failure criterion.…”

Unified Failure Criterion Based on Stress and Stress Gradient Conditions

“…Recently, a unified failure criterion was proposed by the authors' team [34][35][36][37]. The unified failure criterion can be applied to structural members regardless of the existence of notches, as well as their shapes and sizes.…”