Session: 01-10-01: Structures in Extreme Environments

Paper Number: 162426

162426 - Numerical Investigation on Lightning Survivability and Residual Strength of Z-Pinned and Scarf-Patched Cfrp Composites 

Carbon fiber reinforced polymer (CFRP) composites are vulnerable to lightning strikes due to their orthotropic electrical conductivities and poor thermal performance of the polymer matrix. Marginally damaged CFRP composites caused by lightning strikes are typically repaired using the scarf patch method, which offers several key benefits, including enhanced structural integrity, improved load distribution, and the restoration of strength in the locally damaged area. Often, scarf patches are used in combination with z-pins, which can help in preventing delamination and provide enhanced shear strength, to further improve the mechanical properties of repaired CFRP composites. In any case, the survivability of repaired CFRP composites has not been extensively studied, increasing the risk of more severe cumulative failures during subsequent lightning strikes. This study will develop a sequentially coupled modeling framework to understand the effects of scarf patching and z-pinning on the lightning damage and residual flexure strength of an AS4/3506 carbon/epoxy laminate. A nonlinear transient heat transfer model will be initially developed with z-pinned and scarf-patched CFRP composites subjected to a simulated 200 kA peak waveform, predicting thermal damage. Two variables will be considered in the simulations: (1) z-pin material (conductive metal and insulating polymer) and (2) lightning attachment (center and boundaries of the scarf patch). Thermally-damaged regions will be removed from the models prior to the subsequent structural model for residual strength assessment via four-point bending simulation. The extent of lightning thermal damage and corresponding residual flexural strength of the repaired CFRP composites will be compared to those from the baseline model (i.e., pristine CFRP composite). This will provide reliable aerospace composite design assessments that can improve the lightning survivability and structural durability of repaired CFRP composites after lightning strikes.

Presenting Author: Juhyeong Lee Utah State University

Presenting Author Biography: Logan Hales is a graduate student in Mechanical Engineering at Utah State University (USU), where they earned a Bachelor’s Degree in Mechanical engineering from the same institution. With an internship from Idaho National Laboratory (INL) he brings practical experience in systems engineering to his research work. Their research interests focus in composite design and lightning strike behavior with composites under extreme conditions. Their current research is investigating the lightning survivability of z-pinned and scarf-patched composites using finite element analysis (FEA). This research aims to understand the physical process and impacts of lightning on repaired CFRP composites for use in the aerospace industry. In addition with this research he has been involved in confidential projects for the Missile Defense Agency (MDA) conducting similar work. His topics of interest include composites, FEA, material science, and the behavior of materials under extreme conditions.