# Projection-Based Simulation Method for Robotic 3D Printing of Large-Scale Polymer Composite Structures

## TL;DR

This paper introduces a new simulation method for 3D-printed polymer composites that accurately captures material anisotropy from the printing process.

## Contribution

A projection-based finite element method that directly incorporates toolpath-defined fiber orientations into simulations.

## Key findings

- The proposed method achieved a 5% accuracy in predicting deflection of a 20 m-long printed ship structure.
- Printed carbon fiber-reinforced ABS showed strong anisotropy with elastic moduli ranging from 3.2 to 9.8 GPa.
- Shear modulus and strength were measured as 1.17 GPa and 10.9 MPa from off-axis tensile tests.

## Abstract

As large-scale additive manufacturing advances, the reliable prediction of the structural behavior of FDM-printed composites is becoming increasingly important. However, existing finite element methods often oversimplify the material anisotropy introduced by the printing path. This study proposes a projection-based method that maps toolpath-defined fiber orientations directly into a finite element model to represent anisotropic mechanical behavior. The mechanical properties of printed carbon fiber-reinforced ABS were experimentally characterized in three directions (UDL, UDT, and UD10). The results confirmed strong anisotropy, with elastic moduli ranging from 3.2 to 9.8 GPa and tensile strengths from 20 to 81 MPa. The shear modulus and strength obtained from the 10° off-axis tensile tests were 1.17 GPa and 10.9 MPa, respectively. This directional data enabled the implementation of the FE model of a 20 m-long printed ship structure. The predicted mid-span deflection (2.19 mm) differed by only 5% from the experimental measurement (2.08 mm). While effective, this method may face challenges with highly irregular geometries. Nevertheless, it offers a scalable approach for the accurate simulation of FDM-printed composites.