Promotionsthema: Contribution to the investigation of the compressive strength and delamination of continuous fibre laminated composites in the context of competitive sailing <\/strong><\/p>\n Stichw\u00f6rter:<\/strong> CFRP, compressive strength, interlaminar tensile strength, fibre misalignment, automated fibre placement, hand lay-up, nautical sector, strength criteria<\/p>\n Zusammenfassung:<\/strong><\/p>\n Hydrofoils, appendices made from CFRP composite materials, are dimensioned in terms of compressive and out-of-plane tensile strengths. The latter is also called interlaminar tensile strength (ILTS). Compressive stresses are predominantly acting in the lower bearing zone of the hydrofoil. Out-of-plane tensile stresses may cause the hydrofoil elbow to fail by delamination. The determination of both strengths is a challenge, to date. In the last decades, micromechanical failure theories have been developed to describe the fibre-matrix behaviour of laminated structures under compression. One dominating parameter is the fibre misalignment angle as it triggers local matrix instabilities. The ILTS was mainly researched in the aerospace and aeronautical sector, to date. However, it is still an issue that has not been fully understood. Influence of the manufacturing process on the interlaminar tensile strength of thick unidirectional continuous epoxy\/carbon fibre composites<\/em> Abstract:<\/strong> ____________________________<\/p>\n \u00b9 Budiansky, B. & Fleck, N. (1993). Compressive failure of fibre composites. Journal of the Mechanics and Physics of Solids, 41 (1), 183\u2013211. Promotion an der Universit\u00e9 Bretagne Sud und am Institut de Recherche Dupuy de L\u00f4me in\u00a0Lorient, Frankreich Promotionsthema: Contribution to the investigation of the compressive strength and delamination of continuous fibre laminated composites in the context of competitive sailing Stichw\u00f6rter: CFRP, compressive strength, interlaminar tensile strength, fibre misalignment, automated fibre placement, hand lay-up, nautical sector, strength..<\/p>\n
\nThe present work is divided into two parts. The first part is devoted to the confrontation of two experimental methods to determine the compressive strengths of seven different CFRP materials, frequently used in the nautical sector. The focus will be on the determination of the fibre misalignment angle using Yurgartis\u2019 method. The compressive strengths will be confronted with regard to the spatial fibre alignment distributions. The second part deals with the comparison of the ILTS of unidirectional CFRP L-beam specimens, fabricated by hand lay-up and by automated fibre placement (AFP) technology. Four-point-bending tests were carried out. The ILTS was then determined using Lekhnitskii\u2019s and Kedward\u2019s solutions. Finite element simulations confirmed the estimated results. Higher ILTS values of AFP L-beam specimens were discussed and related to the manufacturing process, especially to the compaction mode.<\/p>\nVer\u00f6ffentlichung<\/h3>\n
\nM. Grabow, V. Keryvin, A. Marchandise, J.-C. Grandidier, C. Baley, C. Le Guennec, O. Fagherazzi
\nin Composites Part A: Applied Science and Manufacturing, Elsevier, 03\/2022<\/p>\n
\nRacing yachts that fly over the sea level use appendices called hydrofoils made out of carbon fibre reinforced <\/span>plastics. This study discusses the influence of the manufacturing process on their interlaminar tensile strength <\/span>(ILTS). Indeed, ILTS is a key design parameter, since tensile out-of-plane stresses in the hydrofoil elbow may <\/span>cause the structure to fail by delamination. Hydrofoils are usually manufactured by traditional hand lay-up <\/span>and more recently by automated fibre placement technology (AFP). <\/span>Thick unidirectional L-beam specimens were manufactured from the same prepreg material, either by AFP <\/span>or by hand lay-up (MAN). AFP specimens were<\/span> 40%<\/span> stronger than MAN ones. The investigation of failure <\/span>locations as compared to estimated ones made us highlight that AFP specimens reach their highest possible <\/span>strength while MAN specimens fail prematurely, due to manufacturing-induced defects, such as localised <\/span>porosities. The key features of AFP technology, with respect to the traditional MAN process, are eventually <\/span>discussed.<\/span><\/p>\n
\n\u00b2 Grandidier, J.-C., Casari, P., & Jochum, C. (2012). A fibre direction compressive failure criterion for long fibre laminates at ply scale, including stacking sequence and laminate thickness effects. Composite Structures, 94 (12), 3799\u20133806.
\n\u00b3 Yurgartis, S. (1987). Measurement of small angle fiber misalignments in continuous fiber composites. Composites Science and Technology, 30 (4), 279\u2013293.<\/p>\n","protected":false},"excerpt":{"rendered":"