Method for determining possibility of ignition hazard

Abstract

The invention proposes a method (400) for determining a likelihood (1640) of an ignition hazard. The method (400) includes receiving a current waveform (410) of a lightning strike event (332) at a conductive member (310) forming an interface (322) with a decomposable member (320). A material parameter input (420) is received for the conductive member (310) and the decomposable member (320). Based at least on the one or more received material parameter inputs and energy from the current waveform (430), heating of the resolvable component (320) is resolved (440) and a number of volatiles (342) within the interface volume (324) is determined (450). A total pressure generation within the interface volume (324) is determined (1620) (460). A probability (1640) of ignition hazard of the lightning strike event (332) is output (470) based on a comparison of the total pressure generation (1620) and a containment pressure threshold (1638) of the interface volume (324).

Description

Technical Field

[0001] The present disclosure relates to the field of aircraft. In particular, the present disclosure relates to mitigating the effects of a lightning strike at an interface between a conductive component and a decomposable component. Background Art

[0002] Aircraft can be built using lightweight materials to optimize performance and fuel economy. For some aircraft, such lightweight materials include carbon fiber reinforced plastic (CFRP), in which strong, lightweight fibers are fixed in a cured resin matrix. Carbon fiber is particularly suitable for fiber composite airframe parts, such as panels. Compared with aluminum alloys commonly used in aircraft and aerospace architecture, CFRP provides a strong and lightweight structure. However, due to the low electrical conductivity of CFRP-based panels, high levels of current from a lightning strike may be undesirably concentrated where two panels are connected together by metal fasteners. Summary of the invention

[0003] A method for determining the likelihood of an ignition hazard is presented. The method includes receiving a current waveform of a lightning strike event at a conductive member that forms an interface with a decomposable member. Material parameter inputs of the conductive member and the decomposable member are received. Based on at least one or more of the received material parameter inputs and the energy of the current waveform, heating of the decomposable member is resolved and a quantity of volatiles within an interface volume is determined. A total pressure generation within the interface volume is determined. Based on a comparison of the total pressure generation with a containment pressure threshold of the interface volume, a probability of an ignition hazard of the lightning strike event is output. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 Various aspects of the example aircraft are shown.

[0005] Figure 2 The aircraft's wing is shown, which comprises a composite structure of multiple panels.

[0006] Figure 3 Shown are fastened joints in various states after a lightning strike.

[0007] Figure 4 A flow chart of an example method of determining the likelihood of an ignition hazard is shown.

[0008] Figure 5 The material properties of the fastened joint are shown.

[0009] Figure 6 The decomposition of a decomposable component over time after a lightning strike event is shown.

[0010] Fig. 7Ais an example graph showing bolt tension for fasteners within a range of nut factors.

[0011] Figure 7B is an example plot showing the probability density over the range of nut coefficients.

[0012] Fig. 8A Bolt preload for example fasteners is shown.

[0013] Figure 8B The lateral pressure applied to the example fastener is shown.

[0014] Figure 8C Fluid penetration pressure applied to example fasteners is shown.

[0015] Fig. 9 An example S-curve is shown illustrating the relationship between probability of rupture and maximum pressure.

[0016] Fig. 10A A cross section of the 0-dimensional model is shown.

[0017] Fig. 10B A top view of the 1D model is shown.

[0018] Fig. 10C An extended axial cross-section of the 1D model is shown.

[0019] Fig.11 A flow chart showing another example method for determining the likelihood of an ignition hazard.

[0020] Fig.12 The moving propagation front of the decomposable components is shown.

[0021] Fig.13A and 13B A method for determining the volume resistivity of a decomposable member having anisotropic conductivity is shown.

[0022] Fig.14A Schematic showing the mass and volume of the decomposable component nodes.

[0023] Fig. 14B Displays the propagation of current through the nodes of the decomposable components.

[0024] Fig.15 Schematic showing the penetration of pressure into the interface.

[0025] Fig.16 An integrated model for determining the probability of rupture at the interface between a conductive component and a decomposable component is schematically shown.

[0026] Fig.17 An example computing system is schematically depicted. DETAILED DESCRIPTION

[0027] Lightning strikes on fastened composite structures in flammable environments can result in ignition hazards, often observed as light / spark emissions. Evaluating new fastening systems, components, or configurations for this spark risk is typically done through large test matrices, which is costly and time consuming. The ability to reliably model these ignition hazards can reduce the costs and lead times typically associated with new fastening systems and failure mode testing.

[0028] As an example, Figure 1 Various aspects of an example aircraft 100 are shown. The aircraft includes a nose portion 104, wing portions 106A and 106B, a fuselage portion 108, and a tail portion 110. Any or all of these aircraft portions may include a lightweight skin 112. In some examples, the aircraft skin may include a fiber composite material. In some examples, the aircraft skin may include a lightweight metal, such as aluminum. The composition of the fiber composite material contemplated herein is generally based on carbon fibers and / or similar conductive materials. Example fiber composite materials include carbon fibers fixed in a polymer or resin. The polymer may be thermosetting in some examples and may be thermoplastic in other examples. Example thermosetting polymer resins may include one or more of epoxyamine resins, polyurethane resins, or acrylamide resins. Such resins may be cured in air. Example thermoplastic polymers include polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), etc.

[0029] Figure 2 An example wing 200 of an aircraft is shown. Wing 200 may be an example of wings 106A and 106B. Wing 200 provides support for a jet engine 202. A fuel tank 204 (in cross-section) is disposed within wing 200. Wing 200 includes a composite structure 206 of a plurality of CFRP panels 208a, 208b, 208c, and 208d. In this example, composite structure 206 includes a portion of an upper wing skin. The CFRP panels are connected together by a plurality of conductive fasteners 210. Each fastener may include an exposed portion, such as a cap, that is susceptible to conducting a large amount of current, such as current from a lightning strike 212.

[0030] Figure 3 The fastening joint 300 is shown in various states after a lightning strike. The fastening joint 300 includes a conductive fastener 310 with a conductive cap 312. The fastening joint 300 further includes one or more CFRP panels 320. Generally, the conductive fastener 310 includes a conductive metal material (such as aluminum, titanium, stainless steel, etc.) and may include bolts and nuts, rivets, blind fasteners, or other fastening devices suitable for mechanically connecting the CFRP panels 320.

[0031] When assembled to fastening joint 300, conductive fastener 310 and CFRP panel 320 form a fastening joint interface 322. A fastener hole 324 is created between conductive fastener 310 and CFRP panel 320, forming an interface volume.

[0032] Thus, the conductive fastener 310 can provide through-thickness conductivity in the CFRP panel 320 along the Z direction (sometimes referred to herein as the vertical direction). In contrast, the layers of the CFRP panel 320 have anisotropic conductivity, wherein current is forced to flow in a direction parallel to the layers in the xy plane. Therefore, when lightning strikes the fastened joint 300, high levels of current may undesirably concentrate at the conductive fastener 310, potentially degrading the integrity of the fastened connection, or causing sparks to be generated at the fastened joint interface 322 and creating an ignition hazard.

[0033] As shown at 330, for a fastener lightning strike 332, the conductive fastener 310 may be struck directly or indirectly by lightning (e.g., the lightning strike point is nearby and the current flows to the fastener), and thus may experience a large current. The current may then flow from the conductive fastener 310 and into the composite panel 320. In some examples, the current may flow from the composite panel 320 and then return to the conductive fastener 310. For a lap joint arrangement, the current may flow from the conductive fastener 310, into the second composite layer, then return to the conductive fastener 310 and out the end of the conductive fastener 310.

[0034] As shown at 340, volatilized gases 342 are formed during a lightning strike on the fastener joint 300 and may cause a pressure increase within the fastener hole 324. In moving from the fastener into the composite structure, the current enters the composite structure through the fastener joint interface 322 and / or through a plasma channel formed between the conductive fasteners 310 through the fastener hole 324. The interface is heated and the CFRP material changes phase, generating some gas that can remain in the fastener hole. The combination of heated air and heated gas can cause pressure to build up within the interface volume. As shown at 350, the volatilized pressurized gas can deform the conductive fastener 310 and penetrate into the fastener joint interface 322.

[0035] As shown at 360, if the fluid pressure is sufficient to overcome the fastener preload 362, the excessive pressure may cause the conductive fastener 310 to rupture, opening the fastener interface 322. This may allow hot gases to escape near flammable areas (such as a fuel tank), creating an ignition hazard.

[0036] Thus, systems and methods are presented herein for modeling pressure rise due to lightning strikes at interfaces between conductive components (e.g., metal fasteners) and decomposable components (e.g., CFRP panels). Models for containment thresholds for such interfaces are also presented. The methods herein compare the outputs of the two models to determine the probability of ignition hazard from a lightning strike event at a fastened joint interface. Thus, these models are able to predict outgassing events (e.g., generation of hot gas in the interface, the ensuing pressure increase, and subsequent breach of containment) using multiphysics simulations using test-determined material parameter inputs.

[0037] The systems and methods herein provide several advantages. First, they can be used to quickly evaluate new fastening systems early in the design cycle and reduce the use of test matrices to only those configurations that are considered to be the most promising. In addition, accurate modeling of ignition hazards can reduce the use of test matrices by evaluating and screening test variable combinations, test configurations, etc. This can reduce the costs and lead times associated with testing new fastening systems, failure modes, etc. The outputs of these models can be further used to evaluate lightning protection characteristics and provide an envelope based on the uncertainty of the input parameters.

[0038] One example provides a physics-based one-dimensional model (1DIM) that uses input current waveforms, material parameters (such as contact resistance), and interface geometry (such as available volume) to calculate the pressure generated within the interface. Related method steps include resolving the heating of the composite material, identifying the phase change of the composite material and the generation of volatiles, and the mixing of gaseous products with air in the interfacial gap (and / or the gap generated due to the phase change) to determine the total pressure generation. The pressure at the interface can be input into a three-dimensional structural model containing a containment threshold through a digital thread, etc. to evaluate whether the containment will be maintained or broken.

[0039] These systems and methods can be used to understand how design parameters affect the pressure, temperature, and volatilization generated at the interface between the conductive component and the decomposable component. In addition, these systems and methods can be extended to higher dimensional pressure rise models, allowing for the treatment of failure modes and random variables, and including models of other failure modes other than pressure rise and other ignition hazards.

[0040] Figure 4 A flow chart of an example method 400 for determining the likelihood of an ignition hazard is shown. The method 400 may be performed by one or more computing devices including one or more storage subsystems and one or more logic subsystems (eg, processors). Fig.17 An example computing device is described.

[0041] At 410, method 400 includes receiving a current waveform of a lightning strike event at a conductive member that forms an interface with a decomposable member. The current waveform may include data related to the example current, such as a waveform stored at a storage device. For example, the current waveform may have a peak current amplitude, an attenuation, and a total integrated energy. The lightning strike event may occur on an exposed cap of the conductive member. In other examples, the lightning strike event may occur at other locations on the conductive member, or occur on the decomposable member and migrate to the conductive member.

[0042] At 420, method 400 includes receiving material parameter inputs of the conductive component and the decomposable component. The received material properties may include one or more of interface geometry, interface volume, material properties of the conductive component, and material properties of the decomposable component. In some examples, the decomposable component includes carbon fiber reinforced plastic.

[0043] Figure 5 The material properties of the fastening joint 500 are shown. The fastening joint 300 can be an example of the fastening joint 500. The fastening joint 500 includes a conductive member 510 having a conductive cap 512. The fastening joint 500 also includes one or more decomposable members 520. When assembled into the fastening joint 500, the conductive member 510 and the decomposable member 520 form a fastening joint interface 522. A fastener hole is generated between the conductive member 510 and the decomposable member 520, forming an interface volume 524.

[0044] like Figure 5 As shown, the material properties of the conductive member 510 include at least mass, volume, density, conductivity, and geometry. The material properties of the decomposable member 520 include at least mass, volume, density, conductivity, geometry, decomposition enthalpy, volume resistance, activation energy, timescale of decomposition, char factor, material properties of volatiles, and contact resistance of a portion facing the interface volume 524. The material properties of the interface volume 524 include at least geometry and volume.

[0045] The material properties of the conductive component 510 and the decomposable component 520 may further include fatigue margin, stress margin, power density, damage, other parameters of the conductive component, methods of mounting the conductive component, and / or other characteristics of the aircraft.

[0046] Back to Figure 4 At 430, method 400 includes calculating based on at least the received material parameter input and the energy from the current waveform. One or more model types may be applied, such as anisotropic material models, phase change material models, decomposition models, electrothermal models, and electrochemical models.

[0047] At 440, such calculations include resolving heating of the decomposable component after the lightning strike event. At 450, the calculations include determining an amount of volatiles generated within the interface volume after the lightning strike event. The amount of volatiles may be determined based at least on a phase change of the decomposable component. In some examples, method 400 may further include receiving one or more of a contact resistance of the interface and a voltage across the interface. One or more of resolved heating of the decomposable component and an amount of volatiles generated within the interface volume may be determined based on one or more of the contact resistance of the interface and the voltage across the interface.

[0048] For typical lightning event timescales, the system is adiabatic (i.e., no heat exchange occurs outside the interface volume), no work is done, and no energy is lost. The mass of the decomposable component is m, and the specific heat capacity is c v , the resistance is R. When a current I is applied through a lightning event, the resistor generates a voltage V.

[0049] For a simplified system, the decomposable components consist of a single material and decomposition is neglected, and the electrical energy of the current can be used only for heating (e.g. Joule heating). The energy balance of the system can be described by equation (1):

[0050] ΔE 系统 =Q 内部 =Q 焦耳 =Q 加热 =∫IV dt =∫mc v dT (Equation 1)

[0051] Where ∫IV dt is the dissipated electrical energy, ∫mc v dT is the heating of the node. The heating of the main material is given by equation (2)

[0052]

[0053] Therefore, based on the input current and knowledge of V or R, the temperature change can be calculated by equation (3) or equation (4).

[0054]

[0055] Extending this to include decomposition, the system energy balance can be described by equation (5).

[0056] ΔE 系统 =Q 内部 =∫IV dt =∫m(T)c v (T)dT+Q 分解 (Equation 5)

[0057] Therefore, electrical energy can be used for both heating and decomposition. The decomposition enthalpy of a material is given by its 分解 Determine. The decomposition enthalpy is a material constant. For example, h分解 It can represent the energy required to decompose one gram of material. The energy consumed in decomposition is also determined by the mass available for decomposition. Both decomposable components and conductive components may undergo decomposition in response to an increase in current and a corresponding increase in temperature. For example, conductive components may experience pitting. However, the specific heat of decomposable components is generally lower than that of conductive components. Among CFRP materials, resins are particularly susceptible to decomposition. The long hydrocarbon chains of the resin undergo a phase change, or volatilization, from a solid to a gaseous state.

[0058] The temperature rise (i.e. the energy consumed in heating) depends on the mass m and the specific heat c v , as shown in equation (6).

[0059]

[0060] The degree of decomposition can be represented by α, such that when α = 0, no decomposition occurs, and when α = 1, all available mass has been decomposed. The energy consumed by the decomposition can be represented by equation (7).

[0061] Q 分解 =∫m 0 h 分解 dα (Equation 7)

[0062] In this relationship, when α = 0, Q 分解 =0; when α=1, Q 分解 =m 0 h 分解 .therefore, Among them, m 0 is the total mass available for decomposition, m is the mass of the remaining mass, and μ is the carbon fraction of the material. Therefore, the increase in α depends on the mass m and the decomposition enthalpy h 分解 This relationship can be expressed by equation (8).

[0063]

[0064] Therefore, the dissipated electrical energy (IV) is equal to the sum of the energy consumed in heating the interface volume and the energy consumed in the decomposition, as shown in equation (9).

[0065]

[0066] As mass decomposes, there is less solid mass to heat, but increased gas heating. Therefore, the solid mass m is temperature dependent. To determine the energy required for decomposition, h can be applied 分解 The definition of , leads to equation (10).

[0067]

[0068] However, in the case of both heating and decomposition, it is not possible to know a priori how much energy is involved in each. Decomposition, like other phase change processes, should depend on the temperature of the material. Decomposition can be represented by the Arrhenius rate law (Equation (11)), which relates temperature to decomposition rate.

[0069]

[0070] Figure 6 An example progression 600 of heating and decomposition of a decomposable component over time following a lightning strike event is shown. An example interface volume 602 includes air 605 and a composite material 610. At 620, a lightning strike event (622) occurs, sending an electric current 624 into the interface volume 602. At 630, the electric current 624 is still being introduced into the interface volume 602. The composite material 610 has decomposed into volatile gases 632 and char 634. According to the ideal gas law, the air within the interface volume heats up, increasing the partial pressure of the air within the volume. The char portion of the decomposition products is explained by the rate law of equation (11). At 640, the electric current through the interface volume 602 has ceased. The composite material 610 has further decomposed into volatile gases 632 and char 634. The volatile gases 632 and air 605 have mixed to form an air-gas mixture 642.

[0071] The composite material is heated and decomposed simultaneously. To determine the relative distribution of energy, equations (9) and (11) can be solved simultaneously. By doing so, it is clear that when the temperature is relatively low, the heating of the nodes dominates and the decomposition rate is relatively slow. The heating is increased until a temperature sufficient to activate the rate law is reached, at which point decomposition dominates. The increase in temperature causes the composite material to move from a state of only heating to a state of decomposition. Therefore, material decomposition is also a temperature-dependent process. This relationship assumes that the contact resistance provides Joule heating and the nodes have a constant volume. If the mass available for decomposition is completely exhausted, either no more heating occurs because there is no current path, or the char and gas in thermal equilibrium are heated. In addition, it is assumed that the input electrical energy is directly transmitted to the solid composite through the contact resistance.

[0072] like Figure 6 The decomposed gas and air in the node mix to create a common pressure in the node as shown in 640. The temperature of the mixture is given by equations (12) (as from energy conservation) and (13).

[0073]

[0074] in represents the newly formed gas at any given point in time, and Represents the existing air-gas mixture at a previous point in time.

[0075] Back to Figure 4 At 460, method 400 includes determining a total pressure generation within the interface volume based on the resolved heating and the determined amount of volatiles. The total pressure generation within the interface volume may be further based on mixing of the gaseous product with air within the interface volume.

[0076] As shown in equation (14), the pressure at the interface volume can be derived using the ideal gas law.

[0077]

[0078] Although Equations 9-14 are implemented in terms of mass equations, equivalent evaluations or frameworks can be used in terms of density.

[0079] Back to Figure 4 At 470 , method 400 includes outputting a probability of ignition hazard of the lightning strike event based on a comparison of the total pressure generation and a contained pressure threshold of the interface volume. In instances where the conductive member is a fastener, the contained pressure threshold may be based at least on the fastener preload.

[0080] A containment model can be run to generate thresholds for ignition hazards. The containment model assumes a structure that is clamped with a finite force. A lightning strike creates a pressurized container that complies with the force created by the pressure. The structure can deform to the point where the clamping breaks, which results in outgassing.

[0081] The output pressure of method 400 can then be compared to a containment threshold. In other examples, the output pressure of method 400 can be used as an input to a containment model to determine whether interface rupture will occur at the operating pressure. Thus, the model can be used to determine a containment threshold and can also be used to determine the probability of containment escape.

[0082] The deformation state of the conductive and decomposable components can be determined using solid mechanics equations that solve for the displacement of the material in the system. Mechanical equilibrium can be defined by equation (15), where t is the surface traction on the faces of the conductive and decomposable components and f is the body force.

[0083] ∫ S tdS+∫ V fdV = 0 (Equation 15)

[0084] This balance can also take into account stress tensors and their symmetries, strain tensors, deformation gradients, material composition tensors, and the configuration of the reference and deformed configurations of the system. Surface tractions can include external forces such as preload and pressure on each element of the system. The total surface traction can be used to solve for the internal stress state, which in turn can be used to solve for the strain state. The strain state provides information about the deformation and can be used to solve for motion inside the model.

[0085] The containment model can be an implicit model in which maximum boundary conditions are applied and the final deformed state is solved. For example, the stress tensor includes the internal pressure. Equation (15) can be viewed as the conservation of energy for the solid materials of the system. The calculation of the current state can include the reference and the current configuration of the material. The applied stress tensor is then applied to the current state to generate a deformed state showing how the material changes due to the stress and strain tensors.

[0086] The accommodation model can take into account various possibilities of the current state. For example, the probability of ignition hazard of a lightning strike event can be further determined based on the uncertainty of the input parameter values, such as the nut factor of the fastener. The in-service nut factor of each fastener can vary over a wide range depending on lubrication, wear and corrosion. Fig. 7A An example graph 700 is shown showing bolt tensions for a range of nut factors from 0.1 (excessive lubrication) to 0.5 (excessive friction). Within this range, bolt tensions (given a torque of 87 inch-pounds and a given diameter of 0.25 inches) vary from 3500 pounds to 700 pounds. Figure 7B An example graph 710 showing the input of an example nut coefficient into the containment model is shown. The nut coefficient in graph 710 varies between 0.1 and 0.3, with a triangular distribution (assuming a mode of 0.2). Through multiple model executions, a range of in-service containment performance can be derived.

[0087] The boundary conditions of the containment model also vary based on the actual characteristics of the fasteners and decomposable components. These conditions can be varied in the containment model to generate a range of potential outcomes. In other words, the pressure at which the system ruptures may vary under specific boundary conditions.

[0088] Figures 8A-8C A fastener 800 is depicted experiencing various boundary conditions. The fastener 800 includes at least a fastener cap 802, a fastener shank 804, a laminate edge 806, a fastener tab 808, and a shank midsurface 810.

[0089] Fig. 8AA fastener preload 812 is shown applied to a surface 810 in a fastener shank 804. The fastener preload 812 can be determined based on at least the configuration of the fastener joint 808. The fastener preload 812 can be further based on the penetration of fluid pressure into the fastener joint 808. The fastener preload 812 can represent the amount of tension put into the fastener, for example, can be based on a nut factor. The fastener preload 812 can vary randomly during use. Therefore, the fastener preload 812 can vary randomly within a range of values ​​that accommodate the model.

[0090] same, Figure 8B A lateral pressure 820 is shown exerted on a fastener shank 804 and a laminate edge 806 within a fastener hole. The preload and other configurations of the fastener 800 may determine the response curve in response to increased lateral pressure.

[0091] Figure 8C Fastener 800 and CFRP substrate 830 are shown in a system that creates interface 832 and interface volume 834. Fluid penetration pressure 836 is applied from interface volume 834 to interface 832. The material properties of fastener 800 and CFRP substrate 830, along with their connection configuration, may affect how fluid penetration pressure 836 affects interface 832 and the integrity of fastener joint 808.

[0092] The output probability may be an S-curve representing the relationship between the ignition hazard probability and the current, wherein the ignition hazard probability is based at least on the uncertainty of the nut factor. Fig. 9 A graph 900 showing an example S-curve of probability of rupture versus maximum pressure is shown. Graph 900 includes a median curve 905, an upper limit 910, and a lower limit 915. Each of median curve 905, upper limit 910, and lower limit 915 is an S-shaped curve such that for each curve, a smaller value of maximum pressure indicates a small or no probability of containing a rupture, and for each curve, a larger value of maximum pressure indicates a large or definite probability of containing a rupture. For example, a pressure of 325 megapascals (MPa) produces a 50% probability of containing a rupture for lower limit 915; while 450 MPa produces a 50% probability of containing a rupture for median curve 905, and 550 MPa produces a 50% probability of containing a rupture for upper limit 910. Thus, for each maximum pressure, a range of probabilities can be output.

[0093] Generally speaking, Figure 4-9 The heating and decomposition of the decomposable component are handled in a 0-dimensional (0DIM) manner. Fig. 10AA cross section of an ODIM model is shown, with a conductive member 1000 having a conductive current input 1002. A decomposable member 1004 forms an interface 1006 with the conductive member 1000, with an interface volume 1008 therebetween. In this configuration, the interface volume is merged into a single unit or ODIM volume. This type of model can generate time dependencies related to pressure and temperature, but does not provide spatial dependencies.

[0094] Adding an extra dimension to the model allows determining the degree to which the interface can be decomposed into decomposable components. Fig. 10B and 10C Examples of one-dimensional (1D) models 1020 and 1022 are shown, respectively. Fig. 10B A top view of a one-dimensional model 1020 is shown, which has a conductive member 1030, a decomposable member 1032, an interface 1034 between the two members, and an interface volume 1036. The decomposable member 1032 is divided into a plurality of nodes 1038. In this example, the dimensions are axisymmetric. Each node has a radial length r and a volume of a torus.

[0095] Fig. 10C An extended axial cross-section of a one-dimensional model 1022 is shown having a conductive member 1040, a decomposable member 1042, an interface 1044 between the two members, and an interface volume 1046. The decomposable member 1042 is divided into a plurality of nodes 1048. In this example, each node has a length l and a volume of a right parallelepiped.

[0096] For any 1DIM model, the node thickness can be set to an appropriate value based on the material of the current input; as a non-limiting example, the node thickness can be set to a few microns. For the first node, at the interface volume opposite the conductive member, there is a high conduction current condition, under which there is enough heat to significantly invalidate the rate law and make decomposition dominant. Decomposing the node results in a larger interface volume and a larger amount of generated gas. The additional gas generates a greater pressure within the interface volume. However, in the case of low conduction current, there may not be any decomposition at all.

[0097] In further examples, the model can be converted to two or three dimensions, which allows for more geometric considerations to be taken into account. For example, if a fastener is misaligned with the surrounding panel, the effects of a lightning strike on such a fastener can only be described in two or three dimensions based on the axis along which the fastener is offset. The added dimensionality allows for a deeper understanding of the temperature-induced decomposition and subsequent pressure rise.

[0098] Fig.11A flow chart of an example method 1100 for determining the likelihood of an ignition hazard is shown. The method 1100 may be performed by one or more computing devices including one or more storage subsystems and one or more logic subsystems (eg, processors). Fig.17 An example computing device is described.

[0099] At 1110, method 1100 includes receiving a current waveform of a lightning strike event at a conductive member that forms an interface with a decomposable member including a series of adjacent nodes. For example, the current waveform may have a peak amplitude, an attenuation, and a total energy. The lightning strike event may occur on an exposed cap of the conductive member. In other examples, the lightning strike event may occur at other locations of the conductive member, or occur on the decomposable member and migrate to the conductive member. In some examples, the decomposable member includes a carbon fiber reinforced plastic (CFRP).

[0100] The decomposable component may include a series of nodes extending outwardly from the interface. Fig. 10B and 10C An example of such a representation is shown. The node thickness can be set so that all nodes have equal length (or radial distance), equal mass, equal volume, etc. In other examples, the nodes can be determined in a nonlinear manner, and such nonlinear configurations may require different resistance models to perform the calculations herein.

[0101] At 1120, method 1100 includes receiving a first contact resistance of a first node of the decomposable component located adjacent to the interface volume. In some examples, method 1100 further includes receiving a volume resistance of the decomposable component. The contact resistance can be determined at the wall of the interface volume, while the volume resistance can be determined for the entire decomposable component. The volume resistance is based on the resistance of the decomposable material. Considering the influence of the interface wall, the contact resistance is generally higher than the volume resistance.

[0102] Go to Fig.12 , at 1200, Fig.12 A top view of a one-dimensional (1DIM) model 1205 is shown having a conductive component 1210, a decomposable component 1212, an interface 1214 between the two components, and an interface volume 1216. In some examples, the decomposable component 1212 comprises a carbon fiber reinforced plastic (CFRP). In some models, the interface volume 1216 can be considered as a closed constant volume. The decomposable component 1212 is divided into a plurality of concentric nodes 1218 that extend outward from the conductive component 1210. A conductive current input 1220 is shown being applied to the conductive component 1210.

[0103] At 1230, Fig.12A linearized version of the one-dimensional model 1205 at a first time stamp is shown. An interface volume 1216 is adjacent to a first node 1232. The first node 1232 is characterized by a contact resistance 1234, and the remaining nodes are characterized by a volume resistance 1236. The volume resistance 1236 can be based on the material properties of the decomposable member 1212 and the radial distance of each node. The first node 1232 is undergoing decomposition to generate a gas 1238.

[0104] When determining the bulk resistance of the decomposable component, in some instances, the material constituting the decomposable component has anisotropic conductivity. For such materials, it is necessary to represent the resistance in a one-dimensional (1DIM) framework in order to simplify the calculation to an isotropic representation, which will correspond to the 1DIM method in an axisymmetric domain.

[0105] In the first instance, Fig.13A A top view of a one-dimensional (1DIM) model 1300 is shown, which has a conductive member 1302, a decomposable member 1304, an interface 1306 between the two members, and an interface volume 1308. The decomposable member 1304 is divided into a plurality of concentric nodes 1310. In this example, the dimensions are axisymmetric. One approach is to simply assume that the material of the decomposable member has an isotropic conductivity. This can be expressed by equation (16).

[0106]

[0107] In the second instance, Fig. 13B A top view of a one-dimensional model 1320 is shown, which has a conductive member 1322, a resolvable member 1324, an interface 1326 between the two members, and an interface volume 1328. The resolvable member 1324 is divided into a plurality of concentric nodes 1330. In this example, the dimensions are axisymmetric. In this method, anisotropic conductivity is included in the resistance estimation. This can be expressed by equation (17).

[0108]

[0109] In this example, the calculation actually uses shadows of the conductive members. For a strip material like CFRP, the conductivity will tend to flow along the strips (like CFRP) because the conductivity along the strips is higher than the conductivity in the transverse direction. This allows the three-dimensional effects to be scaled into a one-dimensional model. Both the shadowing and scaling methods are actually valid approximations of the volume resistance, but are valid for different materials and different anisotropies.

[0110] Back to Fig.11At 1130, method 1100 includes determining, at a first time stamp, a first pressure within the interface volume based at least on the first contact resistance. In some examples, the first pressure can be further based on the volume resistance. For example, Figure 4 The pressure is determined based on the heating and decomposition. The pressure is further determined based on material parameter inputs including at least interface geometry, interface volume, material properties of the conductive component, and material properties of the decomposable component.

[0111] The material properties of the decomposable component include at least a mass of each node and a specific heat capacity of each node. Determining the first pressure includes at least resolving heating of the decomposable component after the lightning strike event and determining an amount of volatiles generated within the interface volume after the lightning strike event.

[0112] In the first instance, Fig.14A A top view of a one-dimensional model 1400 is shown, which has a conductive member 1402, a decomposable member 1404, an interface 1406 between the two members, and an interface volume 1408. The decomposable member 1404 is made of CFRP and is divided into a plurality of concentric nodes 1410. Each concentric node 1410 can be described by a volume V and a mass m, where m j =V j ρ CFRP For this axisymmetric model 1400 , the available mass at each node varies with volume, for example, the mass increases as the node moves radially outward from the conductive member 1402 .

[0113] Fig. 14B describes how each node dissipates electrical energy from a lightning strike event. At 1420, node j has a contact resistance R j 、Mass m j and specific heat capacity c v At 1430, node j+1 has a radius that depends on the node radius (r j+1 ) volume resistance R 体积 、Mass m j+1 and the specific heat capacity c, which depends on the node temperature (T) v Likewise, at 1440, node j+2 has a volume resistance R 体积 、Mass m j+2 and the specific heat capacity c, which depends on the node temperature (T) v .

[0114] For each node, energy based on the current I is taken as input. If the temperature of the node is below the threshold temperature required to activate the rate law based on the node material composition, heating dominates and decomposition proceeds slowly. Heating is performed until the threshold temperature, and then decomposition dominates. Therefore, the dissipated electrical energy (IV) is equal to the sum of the energy consumed by heating the interface volume and the energy consumed by decomposition, as shown in equation (18).

[0115]

[0116] The decomposition rate can be described by equation (19).

[0117]

[0118] The electrical energy dissipated at each node can be described similarly to Equation 9, except that the radial coordinate (r) is updated as the propagation front moves outward from the conductive member. This node-by-node modeling provides spatial information about where decomposition occurs within the decomposable member 1404. Another benefit of this modeling is that some assumptions are reduced, such as a priori assumptions about the level of mass decomposition. When implementing node-by-node modeling, some assumptions include that current flows equally through all nodes, contact resistance is only applied to the first node (e.g., the decomposition front), and the rest of the decomposable nodes have a volume resistance based on their distance from the conductive member. The mass of each node is determined by the unit volume, and all mass is available for decomposition. The interface volume has a constant volume. In addition, once a node is exhausted, it is excluded from the remaining iterations.

[0119] Back to Fig.11 At 1140, method 1100 includes receiving a second contact resistance of a second node adjacent to the first node after determining that the first node is completely depleted. Fig.12 , at 1250, Fig.12 A linearized version of the one-dimensional model 1205 is shown at a second time stamp. At this second time stamp, the first node 1232 has been completely depleted. As the first node 1232 decomposes, the decomposition front moves to the adjacent second node 1252, and the contact resistance 1254 also changes accordingly. The decomposition front can be identified based on the node, where 0<α<1. When the adjacent second node 1252 is completely depleted, the contact resistance moves to the next most adjacent node. The bulk resistance 1236 of the remaining nodes remains unchanged. When the input energy drops below a predetermined threshold due to energy depletion or the end of the current pulse, the decomposition front propagation stops.

[0120] Regardless, the decomposition front propagation and associated contact resistance are calculated for each time stamp, regardless of whether the cell behind the propagation front is depleted. When the material behind the propagation front is depleted, the calculation moves to the next cell. The current dominates the contact resistance, especially at the time point immediately after the lightning event. As the propagation front moves outward and the current weakens, the contact resistance at each node may change.

[0121] Nodes that are far from the decomposition front may decompose if the current and volume resistance generate enough heat to initiate decomposition. However, these gases will not enter the interface volume until and unless the nodes are connected to the interface volume by propagation of the decomposition front. This decomposition uses up the energy available from the conduction current input.

[0122] At 1150, method 1100 includes determining, at a second time stamp, a second pressure within the interface volume based at least on the second contact resistance. In some examples, the second pressure may be further based on the volume resistance. The second pressure may be further based on at least material parameter inputs including at least interface geometry, interface volume, material properties of the conductive member, and material properties of the decomposable member.

[0123] At 1160, method 1100 includes determining a maximum pressure of each current waveform within the interface volume based on at least the first pressure and the second pressure. In some examples, determining the maximum pressure of each current waveform within the interface volume includes determining a stopping point of a decomposition front in response to energy depletion of the current waveform.

[0124] The method 1100 may further include receiving additional contact resistances at a plurality of additional time stamps. The pressure may be modeled at each time stamp. Thus, a certain time stamp will have the maximum pressure for the lightning strike event. The maximum pressure in the interface volume may be used to determine the extent of movement of the fastener head and how much the composite material has moved relative to the fastener at the interface of the two components. This may provide information on the probability of rupture, as determined by a containment model within the uncertainty of the material. For a given fastener system, when a certain maximum pressure is reached at the interface, a percent chance of failure or a confidence interval may be output.

[0125] Therefore, the method 1100 may further include outputting a probability of ignition hazard of the lightning strike event based on a comparison of the maximum pressure of each current waveform within the interface volume with a containment pressure threshold of the interface volume. The containment pressure may be as follows: Figure 4 Said determination.

[0126] Gas permeating into the interface between the conductive member and the decomposable member can be modeled using a pressure permeation interaction model, which simulates a fluid permeating into the interface. In some instances, the fluid may not be modeled directly, but rather implemented as a pressure boundary condition. The model may take into account the amount of force present at the interface between the two materials and the pressure of the gas to determine if the pressure is sufficient to cause the gas to leak into the interface. Back Figure 3 , the fluid contact is generating a pressure rupture at 340. When the fluid pressure reaches the edge of the conductive member head, the containment rupture can be determined based on mechanical balance.

[0127] Fig.15 A one-dimensional (1DIM) model 1500 of fluid penetration between a conductive member 1502 and a decomposable member 1504 is shown. The conductive member 1502 and the decomposable member 1504 are each divided into a plurality of nodes extending outward from the center of the conductive member 1502. Three nodes (1506, 1508, and 1510, shown as three nodes, but more or fewer nodes may be included in other examples) of the conductive member 1502 are labeled. Fluid pressure 151 is indicated as penetrating between the conductive member 1502 and the decomposable member 1504.

[0128] Depending on whether the fluid pressure (f) exceeds the critical pressure of the interface, the node can be marked as open or closed. When a node is indicated as an open node (such as node 1506), the fluid pressure is also applied to the nearest neighboring nodes indicated as closed. Using the node shape function (N 1 ,N 2 ,N 3 ) calculates the total force applied to the element. In this example, P 1 =fN 1 +fN 2 and P 2 =fN 2 .

[0129] Fig.16 An integrated model 1600 for determining the probability of rupture at an interface between a conductive component and a decomposable component, such as a conductive fastener and a CFRP panel, is schematically shown. The integrated model 1600 includes a pressure rise model 1602 and a containment model 1604.

[0130] Pressure rise model 1602 includes a plurality of inputs 1610. Inputs 1610 include material properties (e.g., Figure 5 The invention relates to a method for producing a plurality of contact resistances, for example, a plurality of contact resistances, and a plurality of contact resistances. The contact resistances may be selected from a plurality of contact resistances, and the plurality of contact resistances may be selected from ...

[0131] Input 1610 may provide information for model parameters 1612. Model parameters 1612 include the bulk resistance of the decomposable material, the total energy available to the current waveform, and the spatial evolution of the decomposable components.

[0132] The pressure rise model may further include model dimensions 1614, such as 0D, 1D, 2D, etc. Model dimensions 1614 may provide information for how downstream calculations are performed, how the model evolves over time, and the like.

[0133] Input 1610, model parameters 1612, and model dimensions 1614 may be used to calculate separation processing 1616. Separation processing 1616 may include Joule heating of decomposable materials, phase changes of decomposable materials, and heating of gases in the interface volume. The phase changes of the decomposable materials may provide information on the amount and characteristics of volatile gases in the interface volume. Mixing laws may provide information on the heating of the mixture of air and volatile gases. Such mixing laws may be derived based on first principles of thermodynamics. In addition to heating energy and decomposition, spatial energy transfer, such as heat conduction, may also be calculated, resulting in energy losses, conduction losses, etc.

[0134] The separate processes 1616 can be combined to determine a time-dependent output 1618. The time-dependent output 1618 can include temperature rise, decomposition, and pressure rise over time. The pressure rise over time can then be used to determine a maximum pressure prediction 1620.

[0135] The containment model 1604 includes a plurality of material inputs 1630. The material inputs may include material properties of the conductive components, decomposable components, and interface volumes, such as Figure 5 The model parameters 1632 may include the pressure range to be evaluated.

[0136] Uncertainty 1634 may include ranges of preload parameters—such as Figures 8A-8C As described above, and the value range of material input 1630. The time-dependent evolution 1636 may include pressure over time and fluid penetration over time, such as Fig.15 The output of the time-dependent evolution 1636 may be an accommodation threshold 1638. Fig. 9 As described above, the accommodation threshold may be output as an S-curve with upper and lower limits.

[0137] The maximum pressure prediction 1620 and the containment threshold 1638 may then be compared and a rupture probability 1640 output may be determined. The rupture probability 1640 may include one or more probability ranges. The rupture probability 1640 relates the physical base model of the pressure rise model 1602 to the structural model of the containment model 1604 to derive the mechanical response.

[0138] Fig.17Schematically shown is a simplified representation of a computing system 1700 configured to provide any to all of the computing functionality described herein. The computing system 1700 may take the form of one or more personal computers, network accessible server computers, tablet computers, home entertainment computers, gaming devices, mobile computing devices, mobile communication devices (e.g., smartphones), virtual / augmented / mixed reality computing devices, wearable computing devices, Internet of Things (IoT) devices, embedded computing devices, and / or other computing devices.

[0139] The computing system 1700 includes a logic subsystem 1710 and a storage subsystem 1720. The computing system 1700 may optionally include a display subsystem 1730, an input subsystem 1740, a communication subsystem 1750, and / or Fig.17 Other subsystems not shown.

[0140] The logic subsystem 1710 includes one or more physical devices configured to execute instructions. For example, the logic subsystem may be configured to execute instructions as part of one or more applications, services, or other logical structures. The logic subsystem may include one or more hardware processors configured to execute software instructions. Additionally or alternatively, the logic subsystem may include one or more hardware or firmware devices configured to execute hardware or firmware instructions. The processor of the logic subsystem may be single-core or multi-core, and the instructions executed thereon may be configured for sequential, parallel, and / or distributed processing. The individual components of the logic subsystem may optionally be distributed in two or more independent devices, which may be remotely located and / or configured for coordinated processing. Aspects of the logic subsystem may be virtualized and executed by a remotely accessible networked computing device configured for cloud computing.

[0141] The storage subsystem 1720 includes one or more physical devices configured to temporarily and / or permanently store computer information, such as data and instructions executable by the logic subsystem. When the storage subsystem includes two or more devices, the devices can be located in the same place and / or remotely located. The storage subsystem 1720 may include volatile, non-volatile, dynamic, static, read / write, read-only, random access, sequential access, location addressable, file addressable and / or content addressable devices. The storage subsystem 1720 may include removable and / or built-in devices. When the logic subsystem executes instructions, the state of the storage subsystem 1720 may change, for example, storing different data.

[0142] Aspects of logic subsystem 1710 and storage subsystem 1720 may be integrated into one or more hardware logic components. For example, such hardware logic components may include program and application specific integrated circuits (PASIC / ASIC), program and application specific standard products (PSSP / ASSP), systems on chips (SOC), and complex programmable logic devices (CPLD).

[0143] The logic subsystem and the storage subsystem can collaborate to instantiate one or more logical machines. As used herein, the term "machine" is used to collectively refer to a combination of hardware, firmware, software, instructions, and / or any other components that collaborate to provide computer functionality. In other words, a "machine" is never an abstract concept, but always in a tangible form. A machine may be instantiated by a single computing device, or a machine may include two or more subcomponents instantiated by two or more different computing devices. In some implementations, a machine includes a local component (e.g., a software application executed by a computer processor) that collaborates with a remote component (e.g., a cloud computing service provided by a server computer network). The software and / or other instructions that give a particular machine its functionality may optionally be saved as one or more unexecuted modules on one or more suitable storage devices.

[0144] The machine may be implemented using any suitable combination of state-of-the-art and / or future machine learning (ML), artificial intelligence (AI), and / or natural language processing (NLP) techniques. Non-limiting examples of techniques that may be incorporated into the implementation of one or more machines include support vector machines, multi-layer neural networks, convolutional neural networks (e.g., including spatial convolutional networks for processing images and / or videos, temporal convolutional neural networks for processing audio signals and / or natural language sentences, and / or any other suitable convolutional neural network configured to convolve and aggregate features across one or more temporal and / or spatial dimensions), recurrent neural networks (recurrent neural networks), and / or other suitable convolutional neural networks. network) (e.g., long short-term memory networks), associative memories (e.g., lookup tables, hash tables, Bloom filters, neural Turing machines, and / or neural random access memories), word embedding models (e.g., GloVe or Word2Vec), unsupervised spatial and / or clustering methods (e.g., nearest neighbor algorithms, topological data analysis, and / or k-means clustering), graphical models (e.g., (hidden) Markov models, Markov random fields, (hidden) conditional random fields, and / or artificial intelligence knowledge bases), and / or natural language processing techniques (e.g., tokenization, stemming, component and / or dependency parsing, and / or intent identification, segmentation models, and / or hyper-segmentation models (e.g., hidden dynamic models)).

[0145] In some examples, the methods and processes described herein can be implemented using one or more differentiable functions, where the gradient of the differentiable function can be calculated and / or estimated based on the inputs and / or outputs of the differentiable function (e.g., based on training data and / or based on an objective function). These methods and processes can be determined at least in part by a set of trainable parameters. Thus, the trainable parameters of a particular method or process can be adjusted by any suitable training procedure to continually improve the functionality of the method or process.

[0146] Non-limiting examples of training procedures for adjusting trainable parameters include supervised training (e.g., using gradient descent or any other suitable optimization method), zero-shot, few-shot, unsupervised learning methods (e.g., classification based on categories derived from unsupervised clustering methods), reinforcement learning (e.g., feedback-based deep Q-learning), and / or generative adversarial neural network training methods, belief propagation, RANSAC (random sample consensus), contextual bandit methods, maximum likelihood methods, and / or expectation maximization. In some instances, components of multiple methods, processes, and / or systems described herein may be trained simultaneously for an objective function that measures the performance of the collective function of multiple components (e.g., for reinforced feedback and / or labeled training data). Training multiple methods, processes, and / or components simultaneously may improve such collective function. In some instances, one or more methods, processes, and / or components may be trained independently of other components (e.g., offline training based on historical data).

[0147] When display subsystem 1730 is included, it can be used to present a visual representation of the data stored by storage subsystem 1720. This visual representation can take the form of a graphical user interface (GUI). Display subsystem 1730 can include one or more display devices using almost any type of technology. In some implementations, the display subsystem can include one or more virtual, augmented, or mixed reality displays.

[0148] When an input subsystem 1740 is included, it may include or be connected to one or more input devices. An input device may include a sensor device or a user input device. Examples of user input devices include a keyboard, a mouse, a touch screen, or a game controller. In some embodiments, the input subsystem may include or be connected to selected natural user input (NUI) components. These components may be integrated or peripheral, and the transduction and / or processing of input actions may be performed on-board or off-board. Example NUI components may include microphones for speech and / or voice recognition; infrared, color, stereo and / or depth cameras for machine vision and / or gesture recognition; head trackers, eye trackers, accelerometers and / or gyroscopes for motion detection and / or intent recognition.

[0149] When included, the communication subsystem 1750 can be configured to communicatively couple the computing system 1700 with one or more other computing devices. The communication subsystem 1750 can include wired and / or wireless communication devices compatible with one or more different communication protocols. The communication subsystem can be configured to communicate over a personal, local area network, and / or wide area network.

[0150] Furthermore, the present disclosure also includes configurations according to the following clauses.

[0151] Clause 1. A method for determining the likelihood of an ignition hazard, comprising: receiving a current waveform of a lightning strike event at a conductive member that forms an interface with a decomposable member; receiving material parameter inputs of the conductive member and the decomposable member; and based at least on one or more of the received material parameter inputs and the energy of the current waveform: resolving heating of the decomposable member after the lightning strike event; and determining a quantity of volatiles generated within an interface volume after the lightning strike event; determining a total pressure generation within the interface volume based on the resolved heating and the determined quantity of volatiles; and outputting a probability of an ignition hazard of the lightning strike event based on a comparison of the total pressure generation and a containment pressure threshold of the interface volume.

[0152] Clause 2. The method of clause 1, wherein the material parameter input comprises one or more of interface geometry, interface volume, material properties of conductive components, and material properties of decomposable components.

[0153] Clause 3. The method of clause 2 further comprises: receiving one or more of a contact resistance of the interface and a voltage across the interface; and determining one or more of resolved heating of the decomposable component and an amount of volatiles generated within the interface volume based on one or more of the contact resistance of the interface and the voltage across the interface.

[0154] Clause 4. The method of clauses 1 to 3, wherein the conductive member is a fastener, and wherein the containment pressure threshold of the interface volume is based at least on a fastener preload.

[0155] Clause 5. The method of clauses 1 to 4, wherein the fastener preload is determined based at least on a configuration of a joint of the fastener.

[0156] Clause 6. The method of clauses 1 to 5, wherein the fastener preload is further determined based on fluid pressure penetration into a joint of the fastener.

[0157] Clause 7. The method of clauses 1 to 6, wherein the probability of an ignition hazard of the lightning strike event is further based on an uncertainty in a nut factor of the fastener.

[0158] Clause 8. The method of clauses 1 to 7, wherein the decomposable component comprises carbon fiber reinforced plastic.

[0159] Clause 9. The method of clauses 1 to 8, wherein the total pressure generation within the interface volume is also based on mixing of the gaseous product with air within the interface volume.

[0160] Clause 10. A method for determining the likelihood of an ignition hazard, comprising: receiving a current waveform of a lightning strike event at a conductive member, the conductive member forming an interface with a decomposable member comprising a series of adjacent nodes; receiving a first contact resistance of a first node of the decomposable member located adjacent to an interface volume; determining a first pressure within the interface volume at a first timestamp based at least on the first contact resistance; after determining that the first node is completely depleted, receiving a second contact resistance of a second node adjacent to the first node; determining a second pressure within the interface volume at a second timestamp based at least on the second contact resistance; and determining a maximum pressure of each current waveform within the interface volume based at least on the first pressure and the second pressure.

[0161] Clause 11. The method of clause 10, further comprising: outputting a probability of an ignition hazard of the lightning strike event based on a comparison of the maximum pressure of each current waveform within the interface volume and a containment pressure threshold of the interface volume.

[0162] Clause 12. The method of clause 11, further comprising indicating a containment breach based on fluid pressure applied to at least the first node and the second node.

[0163] Clause 13. The method of clauses 10 to 12, wherein determining the first pressure and the second pressure is further based on a volume resistivity of the decomposable member.

[0164] Clause 14. The method of clauses 10 to 13, wherein the material properties of the decomposable component include at least a mass of each node and a specific heat capacity of each node.

[0165] Clause 15. The method of clauses 10 to 14, wherein determining the first pressure comprises at least resolving heating of the decomposable component after the lightning strike event and determining an amount of volatiles generated within the interface volume after the lightning strike event.

[0166] Clause 16. The method of clauses 10 to 15, wherein determining the maximum pressure of each current waveform within the interface volume comprises determining a stopping point of a decomposition front in response to current waveform energy exhaustion.

[0167] Clause 17. The method of clauses 10 to 16, further comprising receiving additional contact resistances at a plurality of additional time stamps.

[0168] Clause 18. The method of clauses 10 to 17, wherein the decomposable component comprises carbon fiber reinforced plastic.

[0169] Clause 19. A system for determining the likelihood of an ignition hazard, comprising: one or more processors; and one or more storage devices storing instructions executable by the one or more processors to: receive a current waveform of a lightning strike event at a conductive member that forms an interface with a decomposable member; receive material parameter inputs of the conductive member and the decomposable member; and based at least on one or more received material parameter inputs and energy from the current waveform: resolve heating of the decomposable member after the lightning strike event; and determine the amount of volatiles generated in an interface volume after the lightning strike event; determine a total pressure generation in the interface volume based on the resolved heating and the determined amount of volatiles; and output a probability of an ignition hazard of the lightning strike event based on a comparison of the total pressure generation with a containment pressure threshold of the interface volume.

[0170] Clause 20. A system according to clause 19, wherein the instructions for determining the total pressure generation within the interface volume also include: receiving one or more of a contact resistance of the interface and a voltage across the interface; and determining one or more of decomposable heating of the decomposable component and an amount of volatiles generated within the interface volume based on one or more of the contact resistance of the interface and the voltage across the interface.

[0171] It should be understood that the configurations and / or methods described herein are exemplary in nature, and these specific embodiments or examples are not considered in a limiting sense, because many variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. Therefore, the various behaviors illustrated and / or described may be performed in the order illustrated and / or described, in other orders, in parallel, or omitted. Likewise, the order of the above-mentioned processing may be changed.

[0172] The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various processes, systems and configurations, and other features, functions, acts, and / or properties disclosed herein, as well as any and all equivalents thereof.

[0173] Parts List:

[0174] Aircraft 100

[0175] Head part 104

[0176] Wing sections 106A, 106B

[0177] Body part 108

[0178] Tail section 110

[0179] Lightweight skin 112

[0180] Wing 200

[0181] Jet Engine 202

[0182] Fuel tank 204

[0183] Composite Structure 206

[0184] CFRP panels 208a, 208b, 208c, 208d

[0185] Conductive fastener 210

[0186] Lightning Strike 212

[0187] Fastening joint 300

[0188] Conductive fastener 310

[0189] Conductive cap 312

[0190] CFRP Panel 320

[0191] Fastening joint interface 322

[0192] Fastener holes 324

[0193] Fastener Lightning Strike 332

[0194] Volatile Gas 342

[0195] Fastener Preload 362

[0196] Method 400

[0197] Method steps 410, 420, 430, 440, 450, 460, 470 fastening joint 500

[0198] Conductive member 510

[0199] Conductive cap 512

[0200] Decomposable component 520

[0201] Fastening joint interface 522

[0202] Interface volume 524

[0203] Progress 600

[0204] Interface volume 602

[0205] Air 605

[0206] Composite Materials 610

[0207] Lightning Strike 622

[0208] Current 624

[0209] Volatile Gas 632

[0210] Carbon 634

[0211] Air-Gas Mixture 642 Figure 700

[0212] Figure 710

[0213] Fastener 800

[0214] Fastener Cap 802

[0215] Fastener shank 804

[0216] Laminate Edge 806

[0217] Fastener joint 808

[0218] Middle surface of handle 810

[0219] Fastener Preload 812

[0220] Lateral pressure 820

[0221] CFRP substrate 830

[0222] Interface 832

[0223] Interface volume 834

[0224] Fluid penetration pressure 836

[0225] Figure 900

[0226] Median Curve 905

[0227] Upper limit 910

[0228] Lower limit 915

[0229] Conductive member 1000

[0230] Conductive current input 1002

[0231] Decomposable component 1004

[0232] Interface 1006

[0233] Interface volume 1008 one-dimensional (1DIM) model 1020, 1022 conductive component 1030

[0234] Decomposable component 1032

[0235] Interface 1034

[0236] Interface volume 1036

[0237] Node 1038

[0238] Conductive member 1040

[0239] Decomposable component 1042

[0240] Interface 1044

[0241] Interface volume 1046

[0242] Node 1048

[0243] Method 1100

[0244] Method steps 1110, 1120, 1130, 1140, 1150, 1160

[0245] One-dimensional (1DIM) model 1205

[0246] Conductive member 1210

[0247] Decomposable components 1212

[0248] Interface 1214

[0249] Interface volume 1216

[0250] Concentric Node 1218

[0251] Conductive current input 1220

[0252] First node 1232

[0253] Contact resistance 1234

[0254] Volume resistance 1236

[0255] Gas 1238

[0256] Second node 1252

[0257] Contact resistance 1254

[0258] One-dimensional (1DIM) model 1300

[0259] Conductive member 1302

[0260] Decomposable component 1304

[0261] Interface 1306

[0262] Interface volume 1308

[0263] Concentric Node 1310

[0264] One-dimensional (1DIM) model 1320

[0265] Conductive member 1322

[0266] Decomposable components 1324

[0267] Interface 1326

[0268] Interface volume 1328

[0269] Concentric Node 1330

[0270] One-dimensional (1DIM) model 1400

[0271] Conductive member 1402

[0272] Decomposable component 1404

[0273] Interface 1406

[0274] Interface volume 1408

[0275] Concentric Node 1410

[0276] One-dimensional (1DIM) model 1500

[0277] Conductive member 1502

[0278] Decomposable component 1504

[0279] Nodes 1506, 1508, 1510

[0280] Fluid Pressure 1512

[0281] Integrated Model 1600

[0282] Pressure Rise Model 1602

[0283] Accommodate model 1604

[0284] Input 1610

[0285] Model parameters 1612

[0286] Model Dimensions 1614

[0287] Separation process 1616

[0288] Time-dependent output 1618

[0289] Maximum pressure prediction value 1620

[0290] Material input 1630

[0291] Model parameters 1632

[0292] Uncertainty1634

[0293] Time-dependent evolution 1636

[0294] Accommodation threshold 1638

[0295] Rupture 1640

[0296] Computing system 1700

[0297] Logic Subsystem 1710

[0298] Storage subsystem 1720

[0299] Display subsystem 1730

[0300] Input Subsystem 1740

[0301] Communications subsystem 1750.

Claims

1. A method (400) for determining a likelihood of an ignition hazard (1640), comprising: (410) receiving a current waveform of a lightning strike event (332) at a conductive member (310) forming an interface (322) with the decomposable member (320); (420) receiving material parameter inputs of the conductive component (310) and the decomposable component (320); and (430) based at least on one or more received material parameter inputs and energy from the current waveform: (440) analyzing the heating of the decomposable component (320) after the lightning strike event (332); and (450) determining an amount of volatiles (342) generated within the interface volume (324) after the lightning strike event (332); (460) determining a total pressure generation (1620) within the interface volume (324) based on the resolved heating and the determined amount of volatiles (342); and (470) outputting a probability (1640) of an ignition hazard of the lightning strike event (332) based on a comparison of the total pressure generation (1620) and a containment pressure threshold (1638) of the interface volume (324).

2. The method (400) of claim 1, wherein the material parameter input comprises one or more of an interface geometry, an interface volume (324), a material property of the conductive member (310), and a material property of the decomposable member (320).

3. The method (400) of claim 1, further comprising: receiving one or more of a contact resistance (1234) of the interface (322) and a voltage across the interface (322); and One or more of the resolved heating of the decomposable member (320) and the amount of the volatiles (342) generated within the interface volume (324) are determined based on one or more of the contact resistance (1234) of the interface (322) and a voltage across the interface (322).

4. The method of claim 1, wherein the conductive member (310) is a fastener, and wherein the containment pressure threshold (1638) of the interface volume (324) is based at least on a fastener preload (362).

5. The method of claim 4, wherein the fastener preload (362) is determined based at least on a configuration of a joint (300) of the fastener.

6. The method of claim 5, wherein the fastener preload (362) is further determined based on fluid pressure penetration (836) into the joint (300) of the fastener.

7. The method of claim 4, wherein the probability (1640) of an ignition hazard of the lightning strike event (332) is further based on an uncertainty (1634) in a nut factor of the fastener.

8. The method of claim 1, wherein the decomposable component (320) comprises carbon fiber reinforced plastic.

9. The method of claim 1, wherein the total pressure generation (1620) within the interface volume (320) is also based on mixing of gaseous products (632) with air (605) within the interface volume (324).

10. A method (1100) for determining a likelihood of an ignition hazard (1640), comprising: (1110) receiving a current waveform of a lightning strike event (622) at a conductive member (1210) that forms an interface (1214) with a decomposable member (1212) including a series of adjacent nodes (1218); (1120) receiving a first contact resistance (1234) of a first node (1232) of the decomposable member (1212) located adjacent to an interface volume (1216); (1130) determining, at a first time stamp, a first pressure within the interface volume (1216) based at least on the first contact resistance (1234); (1140) after determining that the first node (1232) is completely depleted, receiving a second contact resistance (1254) of a second node (1252) adjacent to the first node (1232); (1150) determining, at a second time stamp, a second pressure within the interface volume (1216) based at least on the second contact resistance (1254); and (1160) Determining a maximum pressure (1620) for each current waveform within the interface volume (1216) based at least on the first pressure and the second pressure.

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