polymers Article Low-Velocity Impact Analysis of Pineapple Leaf Fiber (PALF) Hybrid Composites Muhammad Imran Najeeb 1 , Mohamed Thariq Hameed Sultan 1,2,3, * , Ain Umaira Md Shah 1 , Siti Madiha Muhammad Amir 4 , Syafiqah Nur Azrie Safri 2 , Mohammad Jawaid 2 and Mohamad Rabaie Shari 4   Citation: Najeeb, M.I.; Hameed Sultan, M.T.; Md Shah, A.U.; Muhammad Amir, S.M.; Safri, S.N.A.; Jawaid, M.; Shari, M.R. Low-Velocity Impact Analysis of Pineapple Leaf Fiber (PALF) Hybrid Composites. Polymers 2021, 13, 3194. https:// doi.org/10.3390/polym13183194 Academic Editors: Emanoil Linul, Dipen Kumar Rajak and Cristina Vălean Received: 30 June 2021 Accepted: 2 August 2021 Published: 21 September 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Aerospace Engineering, Faculty of Engineering, Universiti Putra Malaysia, UPM Serdang 43400, Selangor Darul Ehsan, Malaysia; muhdimran02@gmail.com (M.I.N.); ainumaira91@gmail.com (A.U.M.S.) 2 Laboratory of Biocomposite Technology, Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia, UPM Serdang 43400, Selangor Darul Ehsan, Malaysia; snasafri@gmail.com (S.N.A.S.); jawaid@upm.edu.my (M.J.) 3 Aerospace Malaysia Innovation Centre (944751-A), Prime Minister’s Department, MIGHT Partnership Hub, Jalan Impact, Cyberjaya 63000, Selangor Darul Ehsan, Malaysia 4 Industrial Technology Division, Malaysian Nuclear Agency, Bangi 43000, Selangor Darul Ehsan, Malaysia; madiha_amir@nuclearmalaysia.gov.my (S.M.M.A.); rabaie@nuclearmalaysia.gov.my (M.R.S.) * Correspondence: thariq@upm.edu.my Abstract: The low-velocity impact behaviour of pineapple leaf fiber, PALF reinforce epoxy composite (P), PALF hybrid (GPG), and four-layer woven glass fiber (GGGG) composite was investigated. As for post-impact analysis, the damage evaluation was assessed through photographic images and X-ray computed tomography, using CT scan techniques. The key findings from this study are that a positive hybrid effect of PALF as a reinforcement was seen where the GPG shows the delayed time taken for damage initiation and propagation through the whole sample compared to GGGG. This clearly shows that the addition of fibers does have comparable composite properties with a fully synthetic composite. Through the visual inspection captured by photographic image, the presence of woven fiber glass mat in GPG presents a different damage modecompared to P. Moreover, CT scan results show extended internal damage at the cross-section of all impacted composite. Keywords: plant fiber; pineapple leaf fiber; PALF; low-velocity impact; computed tomography; composite; damage 1. Introduction Impact damage can compromise performance as well as reliability of composite mate- rials and, therefore, it warrants serious attention. Impact damage can occur either during in-service applications or handling during the manufacturing process. As a composite is subjected to an impact, it will experience a bending stress. The bending properties of a composite can be determined through flexural test. The flexural test provides the compos- ite bending strength and its stiffness. The flexural properties of a composite provides a preliminary insight on the possible impact strength properties of a composite. Generally, literature studies show that when the flexural strength of a hybrid composite is higher than non-hybrid, then the impact strength will have the same kind of result. A study shows that hybrid flax/carbon/epoxy composite has had an improved flexural strength of about 345.191% compared to flax/epoxy, while in impact test, flax/carbon/epoxy has 479.57% higher peak force compared with the flax/epoxy [1]. Besides that, hybrid basalt/glass/epoxy shows 30.35% higher flexural strength compared to basalt/epoxy and, in impact test, basalt/glass/epoxy shows 17.24% improvement of peak force compared to basalt/epoxy [2]. However, more comprehensive studies are needed to see a pattern between flexural and impact strength of a composite. Polymers 2021, 13, 3194. https://doi.org/10.3390/polym13183194 https://www.mdpi.com/journal/polymers