Thermal cycling of strained nickel‐coated glass‐epoxy composite laminates: Effects on macro mechanical and fiber‐matrix interface properties

• Published in: Polymer composites 2023-01, Vol.44 (1), p.550-561
• Main Authors: Roy, Rene, Shin, Joon‐Hyung, Kweon, Jin‐Hwe, Nam, Young‐Woo
• Format: Article
• Language: English
• Subjects: atomic force microscopy; coefficient of thermal expansion; Conditioning; Electroless plating; Energy storage; fiber‐matrix interface; Glass fiber reinforced plastics; Glass-epoxy composites; Interfacial properties; in‐plane shear; Laminates; Mechanical tests; nickel coating; Nickel coatings; Plastic deformation; Polymer matrix composites; Polymers; Reinforcing fibers; Shear strength; Short fibers; Storage capacity; Surface energy; Tensile tests; Thermal cycling; Thermal expansion; thermomechanical; Thermomechanical analysis; Thermomechanical properties; Transition temperature
• ISSN: 0272-8397; 1548-0569
• DOI: 10.1002/pc.27118

Nickel coating of reinforcing fibers via electroless plating can provide superior properties to polymer composites, particularly for radar stealth, although its effect on thermomechanical properties and thermal cycling response are relatively unverified. Thermal cycling of strained nickel‐coated glass fiber epoxy laminates was performed to evaluate its effect through in‐plane shear mechanical testing and fiber‐matrix interface region microscopic observations. Laminates were subjected to 4000 cycles of thermal conditioning (regular and strained). Subsequent in‐plane shear tensile tests revealed a ~10% increase in their ultimate shear strength, which was credited to polymer relaxation and increased plastic energy storage capacity. Atomic force microscopy in force modulation mode showed the most significant fiber‐matrix interface region changes for strained thermal cycled specimens, which we attribute to their higher stress during conditioning and plastic deformation. A relatively short fiber‐matrix interface region length was observed, which we attribute to the lower surface energy of Ni‐glass fiber. Thermomechanical analysis (TMA) revealed a glass‐transition temperature range of 71–110°C, and coefficients of thermal expansion (CTE) were evaluated for several laminate configurations. Nickel‐coated glass fiber epoxy laminates were subjected to 4000 cycles of thermal conditioning (regular and strained). In‐plane shear tensile tests on conditioned specimens revealed a 10% increase in ultimate shear strength. Changes to the fiber‐matrix region were observed with atomic force microscopy in force modulation mode.