Specimen representation on the prediction of artificial test lightning plasma, resulting specimen loading and subsequent composite material damage

Abstract

Preceding work has established that artificial test lightning plasma and composite test specimen damage can be modelled. However, no work has studied the impact of specimen representation in the modelling of the plasma and the resulting impact on specimen damage. Herein four distinct specimen designs have been modelled to understand the impact on plasma properties. The resulting specimen surface loads have then been passed to Finite Element (FE) damage models to predict thermal damage. A magnetohydrodynamic FE multiphysics model is employed to simulate the plasma and a FE thermalelectric modelling approach is used to predict the composite material damage. For the test arrangements modelled herein it has been found that specimen representation has limited impact on plasma global structure, even with significant change in specimen properties (e.g. from copper to epoxy). However, noteworthy variation in the local specimen surface loading is witnessed with specimen property change (e.g. epoxy to carbon reinforced epoxy), with peak magnitudes for surface pressure, velocity, current density and temperature changing by up to 88%. Such variation in local surface loading does significantly vary the prediction of thermal damage depth (up to 1200%) and surface damage area (up to 1314%). This work, for the first time, provides predictions for the thermal damage suffered by both protected and unprotected specimens exposed to test standard Waveform B.

Coupled Thermal-Mechanical Progressive Damage Model with Strain and Heating Rate Effects for Lightning Strike Damage Assessment

“…A mesh of 33,478 elements, with two elements through the thickness of each ply, was developed. Results of a previous publication indicated that most of the moderate and severe damage, generated by thermal-electrical loading, was confined to a region 30 mm from the centre of the specimen [21]. This region enclosed 87% of the moderate damage volume (and all moderate damage below ply two) and 99% of the severe damage (and all severe damage below ply one) as shown in Fig.…”

“…However, to-date these have typically been confined to simulations of a single type of lightning strike physics (thermal-electric, pressure-displacement, thermal-displacement) and have not accounted for the strain and heating rate effects observed during a lightning strike event. Preceding works which have studied the various physics individually indicated that mechanical damage plays an important role during Waveform A and thermal damage plays an important role under Waveform B conditions [15,21]. In general, given the individual physics studied in preceding works, there is limited understanding of the combined role or ratio of damage for the range of physical loading types.…”

“…The same python script methodology, proposed by Foster et al [15], was used to transfer the temperature profile from the thermal-electric to the dynamic, temperature-displacement, explicit simulation. A Waveform B simulation was undertaken by loading the mesh with the plasma simulation outputs from previous publications [21,49]. In this case the temperature-displacement simulation was run for a total of 0.03 ms because at this point the thermal damage had stopped increasing and pressure loading had normalised to atmospheric pressure.…”

“…[1,[3][4][5][6][7]. Research is on-going to model the plasma developed during a strike using Finite element or CFD simulations and the resulting loading to the specimen [8,9,[18][19][20][21][10][11][12][13][14][15][16][17]. The majority of simulation authors have modelled specimen behaviour only and assumed a surface load, employing FE models to characterise the thermal damage [8,10,11,14,16,20] or damage as a result of pressure loading [11][12][13].…”

Understanding the Impact of Standardized SAE Waveform Parameter Variation on Artificial Lightning Plasma, Specimen Loading, and Composite Material Damage

“…Authors have also used FE modelling to predict the likely damaged composite specimen due to incident current, temperature or pressure loading [17], [18], [20], [22], [23], [25], [35]- [37]. However, recently measures have been taken to combine plasma modelling and specimen material damage predictions [21], [24], [35], due to the complexity and computational burden of the required models. Thus limited understanding exists on the influence of plasma modelling on the prediction of specimen damage, and vice versa.…”