{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T20:56:21Z","timestamp":1790110581496,"version":"4.0.1"},"reference-count":37,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2025,11,29]],"date-time":"2025-11-29T00:00:00Z","timestamp":1764374400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>This study situates washed sheep-wool fibres as a sustainable reinforcement candidate for epoxy matrices and evaluates their mechanical response under tensile, flexural, compressive, and Charpy impact loading. The objective of this work is to assess whether short, washed sheep-wool fibres can function as a sustainable reinforcement for epoxy matrices, and to identify optimal fibre length\u2013content windows that improve mechanical behaviour for engineering applications. Moulded\u2013machined specimens were produced with fibre lengths of 3, 6, and 10 mm and contents of 1.0\u20135.0 wt.%, depending on the test; neat epoxy served as the reference. In tension, selected formulations\u2014particularly 10 mm\/1.5 wt.%\u2014showed simultaneous increases in ultimate stress and modulus relative to the neat resin, corresponding to gains of about 10% in ultimate tensile stress and 50% in tensile modulus, at the expense of ductility. In flexure, the modulus decreases by roughly 15\u201335% compared with the matrix, whereas configurations with 3\u20136 mm at 2.5\u20135 wt.% raise the fracture stress by about 35\u201345% and improve post-peak resistance. In compression, reinforcement markedly elevates yield stress, with increases of up to about 160% at 3 mm\/2 wt.%, while the ultimate strain decreases moderately. In Charpy impact, all reinforced materials underperform the resin, with absorbed energy reduced by roughly 75\u201393% depending on fibre length and content, with 3 mm\/1 wt.% being the least affected. A two-factor analysis of variance (ANOVA) indicates that fibre length primarily governs tensile and compressive behaviour, while fibre content dominates flexural and impact responses. Overall, the findings support wool fibres as a viable reinforcement when length and content are optimized, pointing to their use in non-structural to semi-structural industrial components such as interior panels, housings, casings, protective covers, and other parts where moderate tensile\/compressive performance is sufficient and material sustainability is prioritised.<\/jats:p>","DOI":"10.3390\/ma18235391","type":"journal-article","created":{"date-parts":[[2025,12,4]],"date-time":"2025-12-04T16:07:38Z","timestamp":1764864458000},"page":"5391","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Mechanical Performance of Wool-Reinforced Epoxy Composites: Tensile, Flexural, Compressive, and Impact Analysis"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0982-2441","authenticated-orcid":false,"given":"Carlos","family":"Ruiz-D\u00edaz","sequence":"first","affiliation":[{"name":"Department of Mechanical Engineering, University of C\u00f3rdoba, 14071 C\u00f3rdoba, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7627-3385","authenticated-orcid":false,"given":"Guillermo","family":"Guerrero-Vacas","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of C\u00f3rdoba, 14071 C\u00f3rdoba, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9728-258X","authenticated-orcid":false,"given":"\u00d3scar","family":"Rodr\u00edguez-Alabanda","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of C\u00f3rdoba, 14071 C\u00f3rdoba, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,11,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"167","DOI":"10.1016\/j.smallrumres.2005.08.012","article-title":"Mediterranean Sheep and Goats Production: An Uncertain Future","volume":"62","author":"Fois","year":"2006","journal-title":"Small Rumin. Res."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1016\/j.smallrumres.2005.07.043","article-title":"Sheep Production in the World and in Greece","volume":"62","author":"Zygoyiannis","year":"2006","journal-title":"Small Rumin. Res."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Midolo, G., Porto, S.M.C., Cascone, G., and Valenti, F. (2024). Sheep Wool Waste Availability for Potential Sustainable Re-Use and Valorization: A GIS-Based Model. Agriculture, 14.","DOI":"10.3390\/agriculture14060872"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"110765","DOI":"10.1016\/j.jenvman.2020.110765","article-title":"Utilization of Byproducts of Sheep Farming as Organic Fertilizer for Improving Soil Health and Productivity of Barley Forage","volume":"269","author":"Lal","year":"2020","journal-title":"J. Environ. Manag."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"65","DOI":"10.5604\/01.3001.0055.1494","article-title":"Using the Natural Properties of Sheep Wool in the Design of Drought-Reducing Composites","volume":"21","author":"Szczecina","year":"2025","journal-title":"Anim. Sci. Genet."},{"key":"ref_6","unstructured":"European Commission (2012). Life Greenwoolf\u2014Green Hydrolysis Conversion of Wool Wastes into Organic Nitrogen Fertilisers (LIFE12 ENV\/IT\/000439) 2012, European Commission."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2160","DOI":"10.1016\/j.wasman.2009.03.009","article-title":"Wool-Waste as Organic Nutrient Source for Container-Grown Plants","volume":"29","author":"Zheljazkov","year":"2009","journal-title":"Waste Manag."},{"key":"ref_8","unstructured":"European Commission (2020). Circular Economy Action Plan 2020, European Commission."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Karimah, A., Ridho, M.R., Munawar, S.S., Amin, Y., Damayanti, R., Lubis, M.A.R., Wulandari, A.P., and Iswanto, A.H. (2021). A Comprehensive Review on Natural Fibers: Technological and Socio-Economical Aspects. Polymers, 13.","DOI":"10.3390\/polym13244280"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"238","DOI":"10.1177\/0892705719844546","article-title":"Natural Fiber\u2013Reinforced Composites: A Review on Material, Manufacturing, and Machinability","volume":"34","author":"Lotfi","year":"2021","journal-title":"J. Thermoplast. Compos. Mater."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"May, C. (2018). Epoxy Resins: Chemistry and Technology, Routledge. [2nd ed.].","DOI":"10.1201\/9780203756713"},{"key":"ref_12","unstructured":"Petrie, E.M. (2005). Epoxy Adhesive Formulations, McGraw-Hill Professional."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"114739","DOI":"10.1016\/j.matdes.2025.114739","article-title":"Mechanical Analysis of Unidirectional Glass Fibre Reinforced Epoxy Composite Joints Manufactured by Adhesive Bonding and Co-Curing Techniques","volume":"258","author":"Jiang","year":"2025","journal-title":"Mater. Des."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Hudson, T.B., Georgiou, N.A., Smith, A.J., Cano, R.J., and Kang, J.H. (2025). Co-Bonding of Aerospace Composite Joints with Reflowable Adherend Interfaces. J. Compos. Mater.","DOI":"10.1177\/00219983251369766"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1300\/J395v01n03_03","article-title":"A Review on Natural Fibre-Based Composites\u2014Part II: Application of Natural Reinforcements in Composite Materials for Automotive Industry","volume":"1","author":"Puglia","year":"2005","journal-title":"J. Nat. Fibers"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2151","DOI":"10.1177\/00219983241260880","article-title":"Towards Sustainable Composites: Evaluation of Mechanical Properties, Erosion Behavior and Applications of Natural Fiber-Epoxy Composites","volume":"58","author":"Zolfakkar","year":"2024","journal-title":"J. Compos. Mater."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"246","DOI":"10.1016\/j.enbuild.2012.02.014","article-title":"Performance Evaluation and Research of Alternative Thermal Insulations Based on Sheep Wool","volume":"49","author":"Zach","year":"2012","journal-title":"Energy Build."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Patrucco, A., Zoccola, M., and Anceschi, A. (2024). Exploring the Potential Applications of Wool Fibers in Composite Materials: A Review. Polymers, 16.","DOI":"10.3390\/polym16162360"},{"key":"ref_19","first-page":"1412","article-title":"Investigation of Mechanical and Thermal Insulating Properties of Wool Fibres in Epoxy Composites","volume":"29","author":"Semitekolos","year":"2021","journal-title":"Polym. Polym. Compos."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1179","DOI":"10.1016\/S0266-3538(96)00072-3","article-title":"Effects of Fiber Length and Fiber Orientation Distributions on the Tensile Strength of Short-Fiber-Reinforced Polymers","volume":"56","author":"Fu","year":"1996","journal-title":"Compos. Sci. Technol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"329","DOI":"10.1016\/0022-5096(65)90035-9","article-title":"Tensile Properties of Fibre-Reinforced Metals: Copper\/Tungsten and Copper\/Molybdenum","volume":"13","author":"Kelly","year":"1965","journal-title":"J. Mech. Phys. Solids"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Thomason, J.L., and Rudeiros-Fern\u00e1ndez, J.L. (2018). A Review of the Impact Performance of Natural Fiber Thermoplastic Composites. Front. Mater., 5.","DOI":"10.3389\/fmats.2018.00060"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"353","DOI":"10.3390\/micro3010024","article-title":"The Influence of Fibre Cross Section Shape and Fibre Surface Roughness on Composite Micromechanics","volume":"3","author":"Thomason","year":"2023","journal-title":"Micro"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"100488","DOI":"10.1016\/j.jcomc.2024.100488","article-title":"Response of Short Jute Fibre Preform Based Epoxy Composites Subjected to Low-Velocity Impact Loadings","volume":"14","author":"Islam","year":"2024","journal-title":"Compos. Part C Open Access"},{"key":"ref_25","unstructured":"(2020). Plastics\u2014Determination of Tensile Properties\u2014Part 1: General Principles (ISO 527-1:2019) (Standard No. UNE-EN ISO 527-1:2020)."},{"key":"ref_26","unstructured":"(2024). Plastics\u2014Determination of Tensile Properties\u2014Part 4: Test Conditions for Isotropic and Orthotropic Fibre-Reinforced Plastic Composites (ISO 527-4:2023) (Standard No. UNE-EN ISO 527-4:2024)."},{"key":"ref_27","unstructured":"(2020). Plastics\u2014Plastics\u2014Determination of Flexural Properties (ISO 178:2019) (Standard No. UNE-EN ISO 178-1:2020)."},{"key":"ref_28","unstructured":"(2003). Plastics\u2014Determination of Compressive Properties (ISO 604:2002) (Standard No. UNE-EN ISO 604:2003)."},{"key":"ref_29","unstructured":"(2024). Plastics\u2014Determination of Charpy Impact Properties\u2014Part 1: Non-Instrumented Impact Test (ISO 179-1:2023) (Standard No. UNE-EN ISO 179-1:2024)."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"2407132","DOI":"10.1002\/adma.202407132","article-title":"Harnessing Extrinsic Dissipation to Enhance the Toughness of Composites and Composite Joints: A State-of-the-Art Review of Recent Advances","volume":"36","author":"Lubineau","year":"2024","journal-title":"Adv. Mater."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"17594","DOI":"10.1039\/D4RA00149D","article-title":"Synergistic Advances in Natural Fibre Composites: A Comprehensive Review of the Eco-Friendly Bio-Composite Development, Its Characterization and Diverse Applications","volume":"14","author":"Nagaraja","year":"2024","journal-title":"RSC Adv."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"104909","DOI":"10.1016\/j.euromechsol.2023.104909","article-title":"Compressive Failure and Kink-Band Formation Modeling","volume":"99","author":"Larsson","year":"2023","journal-title":"Eur. J. Mech.-A\/Solids"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"114","DOI":"10.1016\/j.compositesa.2008.10.013","article-title":"The Influence of Fibre Length, Diameter and Concentration on the Impact Performance of Long Glass-Fibre Reinforced Polyamide 6,6","volume":"40","author":"Thomason","year":"2009","journal-title":"Compos. Part A Appl. Sci. Manuf."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"107920","DOI":"10.1016\/j.compscitech.2019.107920","article-title":"A Proposal to Modify the Kelly-Tyson Equation to Calculate the Interfacial Shear Strength (IFSS) of Composites with Low Aspect Ratio Fibers","volume":"186","author":"Aliotta","year":"2020","journal-title":"Compos. Sci. Technol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"e39116","DOI":"10.1016\/j.heliyon.2024.e39116","article-title":"Review on the Impact Behavior of Natural Fiber Epoxy Based Composites","volume":"10","author":"Seid","year":"2024","journal-title":"Heliyon"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"107497","DOI":"10.1016\/j.jobe.2023.107497","article-title":"A Critical Review on the Properties of Natural Fibre Reinforced Concrete Composites Subjected to Impact Loading","volume":"77","author":"Wang","year":"2023","journal-title":"J. Build. Eng."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Zhao, X., Li, J., Su, S., and Jiang, N. (2024). Prediction Models of Mechanical Properties of Jute\/PLA Composite Based on X-Ray Computed Tomography. Polymers, 16.","DOI":"10.3390\/polym16010160"}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/18\/23\/5391\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,12,4]],"date-time":"2025-12-04T16:11:58Z","timestamp":1764864718000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/18\/23\/5391"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,11,29]]},"references-count":37,"journal-issue":{"issue":"23","published-online":{"date-parts":[[2025,12]]}},"alternative-id":["ma18235391"],"URL":"https:\/\/doi.org\/10.3390\/ma18235391","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,11,29]]}}}