Mechanical and electrical properties of MWCNT/PP films and structural health monitoring of GF/PP joints

TL;DR

This study explores the use of MWCNT-based nanocomposite and buckypaper films for ultrasonic welding and structural health monitoring of thermoplastic composite joints, demonstrating their effectiveness in damage detection and electrical resistance response.

Contribution

It introduces novel multifunctional MWCNT/PP films and buckypaper for ultrasonic welding and SHM of composite joints, highlighting their improved stability and sensitivity.

Findings

15-20 wt MWCNT films show higher resistance stability

MWCNT/PP films enable effective damage detection

Buckypaper embedded in joints exhibits promising SHM capabilities

Abstract

While welding of thermoplastic composites (TPCs) is a promising rivetless method to reduce weight, higher confidence in joints' structural integrity and failure prediction must be achieved for widespread use in industry. In this work, we present an innovative study on damage detection for ultrasonically welded TPC joints with multiwalled carbon nanotubes (MWCNTs) and embedded buckypaper films. MWCNTs show promise for structural health monitoring (SHM) of composite joints, assembled by adhesive bonding or fusion bonding, through electrical resistance changes. This study focuses on investigating multifunctional films and their suitability for ultrasonic welding (USW) of TPCs, using two approaches: 1) MWCNT/filled polypropylene (PP) nanocomposites prepared via solvent dispersion, and 2) high conductivity MWCNT buckypaper embedded between PP films by hot pressing. Nanocomposite formulations containing 5 wt and 10 wt MWCNTs were synthesized using solvent dispersion method, followed by compression molding to manufacture films. The effect of MWCNT concentration on electrical and dynamic mechanical behavior of multifunctional films was examined with a Sourcemeter and Dynamic Mechanical Analyzer, and a comparison was made between 5 to 20 wt MWCNT-PP films based on previous research. Glass fiber/polypropylene (GF/PP) composite joints were ultrasonically welded in a single lap shear configuration using buckypaper and MWCNT/PP films. Furthermore, electrical resistance measurements were carried out for joints under bending loads. It was observed that 15 wt and 20 wt MWCNT/PP films had higher stability and sensitivity for resistance response than embedded buckypaper and films with low MWCNT contents, demonstrating their suitability for USW and potential for SHM.