A virtual test framework for residual compressive and tensile strength predictions after lightning strikes
Topic(s) : Special Sessions
Co-authors :
Scott MILLEN (UNITED KINGDOM), Xiaodong XU , Juhyeong LEE (UNITED STATES), Adrian MURPHYAbstract :
Composite materials are highly susceptible to lightning strike damage. Increasing experimental and numerical research has been conducted on lightning damage characteristics of composites, with primary focus on idealised standard lightning Waveforms A or D. Direct lightning damage produces several damage modes, including fibre damage (i.e., fray, fracture, or blow-out), matrix damage (i.e., cracking or thermal decomposition) and delamination in carbon fibre-reinforced polymer (CFRP) composites. These damage modes have a deleterious effect on the load carrying capacity of the specimen or structure. Experimental and simulation research has produced a limited number of studies on residual strength following lightning strikes. Experimental works have studied the residual strength post-strike with either tensile, compressive, or flexural testing. However, experimental testing, particularly with artificial lightning strikes, is costly with only a limited number of facilities capable of producing the high currents used in each test configuration. Therefore, the ability of using simulations to predict post-strike residual strength is advantageous.
Therefore, this work presents a new, integrated modelling framework to predict the residual compressive and tensile strengths of carbon/epoxy composite laminates after simulated lightning strikes. A three-stage modelling analysis workflow is developed including sequentially coupled thermal-electric and thermo-mechanical models, to predict both thermal and mechanical damage from a strike, and Compression after Lightning Strikes (CAL) and Tension after Lightning Strikes (TAL) analyses. The delamination and ply degradation information are mapped to compression/tension damage models in ABAQUS/Explicit using python scripts. The residual strength is predicted using a simple maximum stress criterion. Validations are completed for each simulation stage. Lightning-induced thermal damage, resulting from Joule heating, is validated using experimental images. Lightning induced delamination is validated by X-ray Computed Tomography (CT) images. Results show that for a 75 kA Waveform D lightning strike, the predicted thermal damage area is within 7% of the experiment, the predicted thermo-mechanical damage area is within 8% of the experiment and the predicted CAL strength is within 1.2% of the experimental value. The predicted CAL strength for the specimen was 275 MPa, a reduction of 59% from the baseline strength of 666 MPa, while the TAL strength, for the same test case was 513 MPa, a reduction of 44% from the baseline strength of 911 MPa in the literature.
Therefore, this work presents a new, integrated modelling framework to predict the residual compressive and tensile strengths of carbon/epoxy composite laminates after simulated lightning strikes. A three-stage modelling analysis workflow is developed including sequentially coupled thermal-electric and thermo-mechanical models, to predict both thermal and mechanical damage from a strike, and Compression after Lightning Strikes (CAL) and Tension after Lightning Strikes (TAL) analyses. The delamination and ply degradation information are mapped to compression/tension damage models in ABAQUS/Explicit using python scripts. The residual strength is predicted using a simple maximum stress criterion. Validations are completed for each simulation stage. Lightning-induced thermal damage, resulting from Joule heating, is validated using experimental images. Lightning induced delamination is validated by X-ray Computed Tomography (CT) images. Results show that for a 75 kA Waveform D lightning strike, the predicted thermal damage area is within 7% of the experiment, the predicted thermo-mechanical damage area is within 8% of the experiment and the predicted CAL strength is within 1.2% of the experimental value. The predicted CAL strength for the specimen was 275 MPa, a reduction of 59% from the baseline strength of 666 MPa, while the TAL strength, for the same test case was 513 MPa, a reduction of 44% from the baseline strength of 911 MPa in the literature.