Modelling of mechanical response of weldlines in injection-moulded short fibre-reinforced polymer components

Nabergoj, Matija (author), Urevc, Janez (author), Halilovič, Miroslav (author)

Short fibre-reinforced polymers (SFRPs) are increasingly used in structural applications where mechanical integrity under complex loading is critical. However, conventional modelling approaches often fail to accurately predict mechanical behaviour in weldline regions formed during injection moulding, where microstructural anomalies and pre-existing damage significantly degrade performance. This study addresses these limitations by extending a hybrid micro–macromechanical constitutive framework to incorporate localised initial damage at weldlines. Calibration and validation of the model were conducted using directional tensile tests on dumbbell-shaped polyamide 66 specimens reinforced with 25 wt% glass fibres, featuring controlled weldline geometry. Digital image correlation (DIC) was employed to capture strain fields, while injection moulding simulations provided fibre orientation distributions and weldline positioning. Results demonstrate that incorporating initial damage and its independent evolution for the cold weld region significantly improves prediction accuracy in weldline zones without compromising model efficiency. The proposed approach can be integrated seamlessly with existing finite element framework and offers a robust solution for simulating SFRP components with weldlines, enhancing reliability in safety-critical applications.

• Language: English
• Keywords: short-fibre-reinforced polymers, weldline modelling, material damages, fibre orientation, injection moulding, process simulation, constitutive modelling, digital image correlation
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 20 str.
• Numbering: Vol. 17, no. 19, art. 2712
• PID: 20.500.12556/RUL-174953
• UDC: 531:678.7:519.6
• ISSN on article: 2073-4360
• DOI: 10.3390/polym17192712
• COBISS.SI-ID: 252711171
• Publication date in RUL: 10.10.2025

Record is a part of a journal

• Title: Polymers
• Shortened title: Polymers
• Publisher: MDPI
• ISSN: 2073-4360
• COBISS.SI-ID: 517951257

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: polimeri, modeliranje zvarne linije, poškodbe materiala, usmerjenost vlaken, brizganje materialov

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P2-0263
• Name: Mehanika v tehniki