Effect of carbon fiber and thermoplastic resin on laminates under lightning and dielectric strength tests

Abstract

The incorporation of carbon fiber (CF) and thermoplastic resin in wind turbine rotor‐blade represents a challenge for lightning events because CF conducts electricity and the behavior of thermoplastic resins is not well known. A comparative study with laminates with epoxy or thermoplastic resins was performed, using lightning and dielectric strength tests. Lightning tests revealed that resins behaved similarly; the current preferentially flowed in fiber direction and in zones with high contact between fibers (e.g., criss‐crossed fibers at panel edges); the level of through‐thickness damage was inversely related to panel thickness; current flow did not affect the tensile properties in fiber direction, but produced a drop in bending strength; the adequate integration of earth terminals in CF laminates was critical for a proper lightning discharge. In dielectric tests, it was concluded that panels with glass fiber covering CF laminates behaved as through‐thickness insulators; the thermoplastic reduced the laminate's dielectric strength, while the incorporation of CF, or laminate aging in a salt spray chamber showed no difference. Electrical resistance tests showed that the results were not dependent on the type of resin, but on the level of fiber‐to‐fiber and fiber‐to‐terminal contact. The lowest linear resistance was obtained in the longitudinal fiber direction, followed by the transverse and through‐thickness ones.

Challenges and Future Recommendations for Lightning Strike Damage Assessments of Composites: Laboratory Testing and Predictive Modeling

“…The last question is related to the relevance of simulated lightning strike tests to composite structures. A lightning strike causes local damage to various types of composite structures, such as protected CFRP composites with expanded copper mesh, unprotected CFRP composites, composites with and without paint layers [24,29,30,[68][69][70][71][72][73][74], composites with vertically interleaved fibers [74], composites containing electrically conductive nanofillers [75][76][77][78] and single-walled CNT tuball paper [79], composites with conductive coatings [80,81], metal-tufted composites [82], thermoset and thermoplastic composites [50,83], sandwiched composites [84], stitched composites [85], scarf-repaired composites [2], composites with mechanical fasteners [27], and adhesively bonded composite [86], as well as full-scale composite structures, such as wind turbine blades [18,[87][88][89]. Although existing simulated lightning strike experimental studies for CFRP composites primarily focused on unprotected and protected composites and composites with mechanical fasteners, the other composite structures are also of significant importance.…”

Study on compressive performances of carbon nanotube film‐protected composite laminates after lightning strike

“…Zhu et al 14 prepared a dual conductive network of nickel‐coated carbon fiber woven fabrics (NI‐CFWF) for lightning strike protection, which remained a residual compression strength of 92.65%, higher than that of non‐protected CFRP which is 87.89%. Saenz et al 15 conducted lightning strike tests on carbon fiber laminates with epoxy or thermoplastic resins Subsequent mechanical tests revealed that the lightning current did not affect the tensile properties, but rather influenced the bending properties. Liu et al 16 developed a nickel‐coated carbon fiber veil capable of retaining high electrical conductivity after delamination, thereby enhancing lightning protection effectiveness.…”