Session: 02-05-01: Session #1: 7th Symposium on Fastening and Joining Research and Advanced Technology

Paper Number: 96827

96827 - Analytical and Computational Modeling of FRP-Metal Joints Made by Ultrasonic Additive Manufacturing 

Joining fiber reinforced polymers (FRP) to metal structural components is a key area of interest as companies seek to replace metal components with FRPs to capitalize on their high specific strength and high specific stiffness. Previous research has developed a process for producing strong FRP-metal joints via ultrasonic additive manufacturing (UAM), and structural tests have been conducted to characterize the mechanical properties of the joints. The joint is created by embedding dry carbon fiber (CF) fabric within aluminum alloy (AA) using the UAM process. The CF fabric extending from the metal can then be laid up with other CF fabric and cured with epoxy to produce a CFRP part with integral metal tabs or flanges for conventional metal-to-metal fasteners. The mechanical interlocking of CF loops in the AA matrix provides direct load transfer, which is different from conventional joining methods where epoxy is the primary load-carrying component of the joint. In this research, an analytical model and a finite element analysis (FEA) model are developed for UAM-produced FRP-metal joints to provide better joint design and application insights based on material properties and joint geometries. The analytical model  first applies the thick-wall cylindrical pressure vessel theory to calculate the stress condition in the embedded fibers with a tensile load.  Then, the Tsai-Wu failure criterion for orthotropic material is utilized to characterize the fracture in the embedded FRP and thus to predict the failure mode when tension is applied to the joint. Comparing the analytical model and experimental results of two different sample configurations, the model is able to predict the failure mode and peak load based on given material properties and joint geometries. The model also indicates that the fracture in the FRP should initiate from the inner corner of the loop where there is maximum stress. Thus, in order to get a more even stress distribution in the FRP, a wider loop is recommended. Further, an FEA model is built using LS-DYNA to simulate the tensile testing of FRP-metal joints. The joints studied in this research are modeled using a shell mesh by homogenizing the hybrid portion of the joint. The FEA model employs a constraint card which is commonly used to model butt welds, with adjusted parameters calculated based on the analytical model and experimental data. The stress maps obtained from the FEA model for two joint designs show similar distributions when compared to measured digital image correlation (DIC) strain maps, indicating that the failure modes match the experimental results. The FEA simulation results agree well with the experimental results for peak load and displacement at fracture, with an error of less than 3%.

Presenting Author: Ningxiner Zhao The Ohio State University

Presenting Author Biography: Ningxiner Zhao is a doctoral student in the Department of Mechanical and Aerospace Engineering at Ohio State University, working under the guidance of Prof. Marcelo Dapino. Her research focus is additive manufacturing of multi-material structures.

Authors:

Ningxiner Zhao The Ohio State University
Hongqi Guo The Ohio State University
Leon Headings The Ohio State University
Marcelo Dapino Ohio State Univ