# A New Double-Inclination Oblique Model to Simulate Drilling of GFRP/Al-Based Stacks: A Thermomechanical Approach

## TL;DR

This paper introduces a new model to simulate drilling of GFRP/Al stacks, showing how stacking order and speed affect thermal damage.

## Contribution

A novel double-inclination oblique model with thermomechanical coupling is proposed to simulate drilling of GFRP/Al stacks.

## Key findings

- Higher spindle speeds increase interfacial temperatures and subsurface thermal damage.
- GFRP-to-Al stacking results in higher interfacial temperatures due to lower thermal conductivity of GFRP.
- An exponential temperature law was derived to predict thermal variation with cutting speed.

## Abstract

This paper reports an investigation of the thermomechanical behavior at the interface of GFRP/Al composite stacks when the stacking arrangement varies. A temperature-coupled damage approach was developed to simulate thermal energy transfer and damage propagation at metallic-to-composite interface. The proposed model was then implemented into ABAQUS/Explicit finite element code using user-defined subroutine VUMAT finely imbricated with VDFLUX. Unlike to previous models, oblique cutting configuration (OCC) involving double-inclination of the tool was proposed to simulate finely the material removal process owing to drill action. Drilling trials involving the cutting speed and the stacking arrangement were conducted to support the proposed approach. The predictions revealed that increasing the spindle speed significantly impacts the temperature distribution and subsurface thermal damage. An exponential temperature law was derived for predicting temperature variation with the cutting speed and identifying thermal saturation at the interface. The sensitivity of the composite behavior to the stacking arrangement (GFRP → Al vs. Al → GFRP) was well highlighted. The results indicated that attacking the structure from the GFRP side results in higher interfacial temperatures due to GFRP’s lower thermal conductivity. These findings contribute to understanding the heat-affected zone in GFRP, and, hence, provide guidance to minimize thermal damage in industrial drilling of the hybrid stacks.