Effect of Glass Fiber Layers in GFRP Skins on the Mechanical Properties and Fracture Toughness of Foam-Core Sandwich Structures

Hanan S. Fahmy^1, , Sara A. soliman¹, Abo-El Hagag A. Seleem², Mohammed Y. Abdellah^{1, 3} and G. T. Abdel-Jaber^{1, 4}

¹Mechanical Engineering Department, Faculty of Engineering, Qena University, Qena 83523, Egypt

²Egyptien Maintenance Company (EMC) Petroleum Ministry Cairo

³Mechanical Engineering Department, College of Engineering, Alasala Colleges, King Fahd Bin Abdulaziz Rd., Dammam 31483, Saudi Arabia

⁴New Assiut University of Technology (NAUT), Assiut 71684, Egypt

Cite this paper:
Hanan S. Fahmy, Sara A. soliman, Abo-El Hagag A. Seleem, Mohammed Y. Abdellah and G. T. Abdel-Jaber. Effect of Glass Fiber Layers in GFRP Skins on the Mechanical Properties and Fracture Toughness of Foam-Core Sandwich Structures. American Journal of Mechanical Engineering. 2026; 14(1):23-29. doi: 10.12691/ajme-14-1-4

Abstract

This study investigates the effect of glass fiber-reinforced polymer (GFRP) skin reinforcement on the mechanical performance of epoxy-based sandwich panels with a rigid Extruded polystyrene foam core manufactured by hand lay-up. The panels were fabricated using Kemapoxy 150 RGL epoxy resin and bidirectional E-glass woven fabric, with the number of GFRP layers per skin varied from one to four while maintaining a constant core thickness. Mechanical characterization was conducted through unnotched tensile tests (ASTM D3039), and center-notched tension tests to assess fracture behavior and damage tolerance. The results indicate that increasing the number of skin layers significantly enhances tensile strength, flexural stiffness, and fracture toughness. The unnotched tensile strength increased by more than 600% when the number of layers was raised from one to four, accompanied by a transition from brittle failure to progressive, damage-tolerant mechanisms. Center-notched specimens exhibited up to a 360% increase in remote failure stress and achieved a maximum critical energy release rate (GIC) of 9.35 kJ/m² at three skin layers, indicating optimal notch resistance. Fractographic analysis using scanning electron microscopy revealed a shift from clean fiber fracture and core exposure in thin skins to extensive matrix cracking, fiber pull-out, and distributed damage in multi-layer configurations, which promotes energy dissipation and crack blunting. Overall, the results suggest that three to four GFRP layers per skin provide an optimal balance between strength, stiffness, and damage tolerance in Extruded polystyrene foam-cored sandwich structures, offering practical design guidelines for lightweight applications in marine, aerospace, and civil engineering sectors.

Keywords:
GFRP sandwich panels Extruded polystyrene foam core vacuum-assisted resin infusion tensile properties fracture toughness center-notched tension

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References:

[1]	L. Almeida-Fernandes, J. R. Correia, and N. Silvestre, "Transverse fracture behavior of pultruded GFRP materials in tension: Effect of fiber layup," Journal of Composites for Construction, vol. 24, p. 04020033, 08 2020.
[2]	M. Mohamed, S. Anandan, Z. Huo, V. Birman, and K. Chandrashekhara, "Flexural behavior and design of GFRP sandwich panels with polyurethane foam core," Construction and Building Materials, vol. 393, p. 132056, 08 2023.
[3]	A. D. Almutairi, Y. Bai, and W. Ferdous, "Flexural behaviour of GFRP-softwood sandwich panels for prefabricated building construction," Polymers, vol. 15, p. 2102, 05 2023.
[4]	H. Tuwair, J. Volz, M. A. ElGawady, M. Mohamed, K. Chandrashekhara, and V. Birman, "Testing and evaluation of polyurethane-based GFRP sandwich bridge deck panels with polyurethane foam core," Journal of Bridge Engineering, vol. 21, p. 04015033, 04 2016.
[5]	Y. Karsandik, B. Sabuncuoglu, M. Sahin, and V. V. Silberschmidt, "Impact behavior of sandwich composites for aviation applications: A review," Composite Structures, vol. 314, p. 116941, 06 2023.
[6]	K. Naresh, K. Shankar, R. Velmurugan, and N. K. Gupta, "Statistical analysis of the tensile strength of GFRP, CFRP and hybrid composites," Thin-Walled Structures, vol. 126, pp. 150-161, 05 2018.
[7]	Z. Han, J. Jang, J. B. R. G. Souppez, M. Maydison, and D. Oh, "Environmental implications of a sandwich structure of a glass fiber-reinforced polymer ship," Ocean Engineering, vol. 298, p. 117122, 04 2024.
[8]	P. Sharafi, S. Nemati, B. Samali, A. Bahmani, S. Khakpour, and Y. Aliabadizadeh, "Flexural and shear performance of an innovative foam-filled sandwich panel with 3-D high density polyethylene skins," Engineering Solid Mechanics, vol. 6, pp. 113-126, 2018.
[9]	X. F. Yao, M. H. Kolstein, F. S. K. Bijlaard, W. Xu, and M. Xu, "Tensile strength and fracture of glass fiber-reinforced plastic (GFRP) plate with an eccentrically located circular hole," Polymer Testing, vol. 22, pp. 955-963, 12 2003.
[10]	A. R. Torabi, M. A. Motamedi, B. Bahrami, M. Noushak, S. Cicero, and J. A. Álvarez, "Determination of translaminar notch fracture toughness for laminated composites using Brazilian disk test," Polymers, vol. 14, p. 3246, 08 2022.
[11]	R. Shrivastava and K. K. Singh, "Interlaminar fracture toughness response of notched glass/epoxy composite," Materials Today: Proceedings, vol. 106, pp. 160-166, 2024.
[12]	Z. Salleh, M. M. Islam, J. A. Epaarachchi, and H. Su, "Mechanical properties of sandwich composite made of syntactic foam core and GFRP skins," AIMS Materials Science, vol. 3, pp. 1704-1727, 2016.
[13]	"ASTM D3039/D3039M-17 Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials," 2017.
[14]	J. C. Newman, Jr. and M. J. Haines, "Verification of stress-intensity factors for various middle-crack tension test specimens," Engineering Fracture Mechanics, vol. 72, pp. 1113-1118, 05 2005.
[15]	C. Soutis, P. T. Curtis, and N. A. Fleck, "Compressive failure of notched carbon fibre composites," Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences, vol. 440, pp. 241-256, 01 1993.
[16]	N. P. Polyamide (PA, Processing and Applications. Special Chem– Plastics. Available at: https:// www.specialchem.com/ plastics/guide/polyamide-pa-nylon and a. D. 2025).
[17]	Y. Mohammed, M. K. Hassan, H. A. El-Ainin, and A. Hashem, "Effect of stacking sequence and geometric scaling on the brittleness number of glass fiber composite laminate with stress raiser," Science and Engineering of Composite Materials, vol. 21, pp. 281-288, 2014.
[18]	M. Al Ghazal, G. Chahine, and B. White, "Thermal and mechanical insights into sandwich structures: A comparison of XPS foam and Prisma composite cores," Journal of Sandwich Structures and Materials, vol. 27, pp. 1584-1602, 2025.
[19]	T. P. Sah, A. W. Lacey, H. Hao, and W. Chen, "Numerical study of the shear performance of pultruded square glass fibre reinforced polymer connectors in composite prefabricated concrete sandwich panels," Journal of Building Engineering, vol. 119, p. 115262, 02 2026.
[20]	V. K. Srivastava, "Impact behaviour of sandwich GFRP-foam-GFRP composites," International Journal of Composite Materials, vol. 2, pp. 63-66, 2012.
[21]	S. M. R. Khalili, R. K. Mittal, and M. S. Kalani, "Study on flexural resilience of composite foam sandwich panels with polyurethane foam core," AIP Advances, vol. 14, p. 125105, 12 2024.
[22]	Zwick/Roell, "Materials testing machine with hydraulic drive," 2022.
[23]	M. K. Hassan, M. Y. Abdellah, S. K. Azabi, and W. Marzouk, "Fracture toughness of a novel GLARE composite material," International Journal of Engineering and Technology, vol. 15, pp. 36-41, 2015.
[24]	M. K. Hassan, Y. Mohammed, and H. Abu El-Ainin, "Improvement of Al-6061 alloys mechanical properties by controlling processing parameters," International Journal of Mechanical and Mechatronics Engineering, vol. 12, pp. 22-29, 04 2012.
[25]	H. Fouad, A.-H. I. Mourad, B. A. Alshammari, M. K. Hassan, M. Y. Abdallah, and M. Hashem, "Fracture toughness, vibration modal analysis and viscoelastic behavior of Kevlar, glass, and carbon fiber/epoxy composites for dental-post applications," Journal of the Mechanical Behavior of Biomedical Materials, vol. 101, p. 103456, 2020/01/01/ 2020.
[26]	H. A. EI-Aini, Y. Mohammed, and M. K. Hassan, "Effect of mold types and cooling rate on mechanical properties of Al alloy 6061 within ceramic additives," in Second International conference of Energy Engineering; ICEE-2, 2010.
[27]	M. Y. Abdellah, M. G. Sadek, H. Alharthi, and G. Abdel-Jaber, "Mechanical, thermal, and acoustic properties of natural fibre-reinforced polyester," Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering, vol. 238, pp. 1436-1448, 2024.
[28]	M. Y. Abdellah, "A comparative study to evaluate the essential work of fracture to measure the fracture toughness of quasi-brittle material," materials, vol. 15, 2022.
[29]	A. F. G. Mohammed Y. Abdellah, Ahmed F. Mohamed, Ahmed Bakr Khoshaim, "Protection of limestone Coated with Different Polymeric Materials," American Journal of Mechanical Engineering, vol. 5, 2017.
[30]	B. M. F. Mohammed Y. Abdellah , H. M. Abu El-Ainin, Mohamed K. Hassan, Ahmed H. Backar and A. F. Mohamed, "Experimental Evaluation of Mechanical and Tribological Properties of Segregated Al-Mg-Si Alloy Filled with Alumina and Silicon Carbide through Different Types of Casting Molds," metals, 2023.