PSI - Issue 68

ScienceDirect Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 68 (2025) 173–183

European Conference on Fracture 2024 Interlaminar fracture properties of flax fibre biobased composites interleaved with PPS veils European Conference on Fracture 2024 Interlaminar fracture properties of flax fibre biobased composites interleaved with PPS veils Robert Lowe a , Vishnu Prasad a, *, Neal Murphy a , Alojz Ivankovic a a UCD School of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin 4, Ireland Abstract With growing environmental awareness and stringent government regulation, interest in environmentally friendly and recyclable composite materials has increased. Thus, the use of natural fibre-reinforced composites in mechanical and structural applications increased due to their economic and environmental benefits. Improving the interaction between the hydrophilic natural fibre and the hydrophobic matrix is critical to enhancing the mechanical properties and the interlaminar fracture behaviour. Common techniques include fibre surface treatments or the introduction of secondary reinforcements. However, these techniques are often time-consuming and energy-intensive. This project investigates the use of polyphenylene sulphide (PPS) veils, interleaved on a flax fibre bio-resin composite to investigate the interlaminar fracture properties. This avoids complexity and extra energy consumption. The PPS veils are placed at the mid-layer during the composite fabrication. Composites with PPS veils of areal densities of 5 g/m 2 , 10 g/m 2 , and 20 g/m 2 were fabricated using vacuum-assisted resin infusion and compared with the composite without the PPS veils. The Mode I interlaminar fracture toughness increased by 35%, 43%, and 60% respectively with the addition of veils at 5, 10 and 20 g/m 2 . This is attributed to the fibre bridging by the PPS fibres, which consume more energy for delamination. Mode II fracture toughness improved by 1%, 9%, and 13% for respective areal density. The flexural properties were also improved. The flexural strength showed a slight increase in the values by 10 %, 6 % and 15%, whereas the flexural modulus increased by 17%, 13% and 22% respectively with the addition of PPS veils. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers Keywords: Interlaminar fracture toughness; delamination; flax fibre composites; fibre bridging 1. Introduction Natural fibre-reinforced composites (NFRCs) are that category that uses natural fibres such as flex, hemp, and sisal as their reinforcement material (AL-Oqla and Sapuan, 2014). These sustainable composites leverage the strength and © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers Robert Lowe a , Vishnu Prasad a, *, Neal Murphy a , Alojz Ivankovic a a UCD School of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin 4, Ireland Abstract With growing environmental awareness and stringent government regulation, interest in environmentally friendly and recyclable composite materials has increased. Thus, the use of natural fibre-reinforced composites in mechanical and structural applications increased due to their economic and environmental benefits. Improving the interaction between the hydrophilic natural fibre and the hydrophobic matrix is critical to enhancing the mechanical properties and the interlaminar fracture behaviour. Common techniques include fibre surface treatments or the introduction of secondary reinforcements. However, these techniques are often time-consuming and energy-intensive. This project investigates the use of polyphenylene sulphide (PPS) veils, interleaved on a flax fibre bio-resin composite to investigate the interlaminar fracture properties. This avoids complexity and extra energy consumption. The PPS veils are placed at the mid-layer during the composite fabrication. Composites with PPS veils of areal densities of 5 g/m 2 , 10 g/m 2 , and 20 g/m 2 were fabricated using vacuum-assisted resin infusion and compared with the composite without the PPS veils. The Mode I interlaminar fracture toughness increased by 35%, 43%, and 60% respectively with the addition of veils at 5, 10 and 20 g/m 2 . This is attributed to the fibre bridging by the PPS fibres, which consume more energy for delamination. Mode II fracture toughness improved by 1%, 9%, and 13% for respective areal density. The flexural properties were also improved. The flexural strength showed a slight increase in the values by 10 %, 6 % and 15%, whereas the flexural modulus increased by 17%, 13% and 22% respectively with the addition of PPS veils. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers Keywords: Interlaminar fracture toughness; delamination; flax fibre composites; fibre bridging 1. Introduction Natural fibre-reinforced composites (NFRCs) are that category that uses natural fibres such as flex, hemp, and sisal as their reinforcement material (AL-Oqla and Sapuan, 2014). These sustainable composites leverage the strength and

* Corresponding author. E-mail address: vishnu.prasad1@ucd.ie * Corresponding author. E-mail address: vishnu.prasad1@ucd.ie

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers 2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers 10.1016/j.prostr.2025.06.039