Citation: Al Zahmi, S.; Alhammadi, S.; ElHassan, A.; Ahmed, W. Carbon Fiber/PLA Recycled Composite. Polymers 2022, 14, 2194. https:// doi.org/10.3390/polym14112194 Academic Editor: Victor Tcherdyntsev Received: 5 May 2022 Accepted: 24 May 2022 Published: 28 May 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 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/). polymers Article Carbon Fiber/PLA Recycled Composite Salem Al Zahmi 1,2, * , Saif Alhammadi 1 , Amged ElHassan 3 and Waleed Ahmed 4 1 Department of Chemical & Petroleum Engineering, United Arab Emirates University, Al Ain P.O. Box 15551, United Arab Emirates; 201770302@uaeu.ac.ae 2 National Water and Energy Center, United Arab Emirates University, Al Ain P.O. Box 15551, United Arab Emirates 3 Department of Mechanical and Aerospace Engineering, United Arab Emirates University, Al Ain P.O. Box 15551, United Arab Emirates; 201450104@uaeu.ac.ae 4 Engineering Requirements Unit, United Arab Emirates University, Al Ain P.O. Box 15551, United Arab Emirates; w.ahmed@uaeu.ac.ae * Correspondence: s.alzahmi@uaeu.ac.ae Abstract: Due exceptional properties such as its high-temperature resistance, mechanical charac- teristics, and relatively lower price, the demand for carbon fiber has been increasing over the past years. The widespread use of carbon-fiber-reinforced polymers or plastics (CFRP) has attracted many industries. However, on the other hand, the increasing demand for carbon fibers has created a waste recycling problem that must be overcome. In this context, increasing plastic waste from the new 3D printing technology has been increased, contributing to a greater need for recycling efforts. This research aims to produce a recycled composite made from different carbon fiber leftover resources to reinforce the increasing waste of Polylactic acid (PLA) as a promising solution to the growing demand for both materials. Two types of leftover carbon fiber waste from domestic industries are handled: carbon fiber waste (CF) and carbon fiber-reinforced composite (CFRP). Two strategies are adopted to produce the recycled composite material, mixing PLA waste with CF one time and with CFRP the second time. The recycled composites are tested under tensile test conditions to investigate the impact of the waste carbon reinforcement on PLA properties. Additionally, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier-transformed infrared spectroscopy (FTIR) is carried out on composites to study their thermal properties. Keywords: carbon fiber-reinforced polymer composites; pure carbon fiber; mechanical treatment; tensile strength 1. Introduction Plastic consumption has increased rapidly in several fields. As a result, waste genera- tion has increased during the last century. The generation of waste is not only a challenge for humanity but also a major issue for the stability of the whole ecosystem [1]. Therefore, researchers are encouraged to work on environmental solutions to the problem of collecting and increasing waste of polymeric materials to protect the earth’s natural resources and to develop a sustainable society. Several suggestions have arisen in response to studies by researchers including curbing the use of plastics, applying bio-degradable plastic materi- als, shifting towards non-plastic materials, etc., according to the needs of the society [2]. Proposals for a sudden shift to remove plastics from the world, however, is criticized by many sectors, including products and services, because a drastic shift may cause economic instability in the world due to the linkage of a wide variety of economic and social strings with the plastic industry [3]. Therefore, the application of biodegradable plastics has been presented as the most viable solution according to the current situation by both researchers and industrialists [4]. This nod by the main stakeholders and interest of the public towards the conservation of Polymers 2022, 14, 2194. https://doi.org/10.3390/polym14112194 https://www.mdpi.com/journal/polymers