No abstract

Satellites and spacecraft in orbit can impact micrometeorites and other debris at velocities exceeding thousands of meters per second. The shock pressures and temperatures created by these hypervelocity impacts greatly surpass standard material strengths, and deform structures in unconventional failure modes. Under these extreme conditions and strain rates, plastic deformation of a solid can resemble viscous fluidic motion. Using meshless finite element analysis methods, the present research attempts to quantify this fluidic structural response and identify analogous interactions in fluid dynamics.

In a hypervelocity impact (HVI) event, the shock pressures exceed the strength of common aerospace materials, and brief shock-induced temperature rises cause melting and vaporization of most structural bodies. Under these extreme conditions, the failure and deformation of solids can resemble fluid flow. By using meshless Lagrangian models in an explicit computational framework, this work identifies analogous fluidic interactions and further quantifies the role of shear and inertial forces in HVIs.

Satellites and spacecraft in orbit can impact micrometeorites and other debris at velocities exceeding thousands of meters per second. The shock pressures and temperatures created by these hypervelocity impacts greatly surpass standard material strengths, and deform structures in unconventional failure modes. For isotropic materials, flow stress constitutive relations have seen reasonable success in modeling such scenarios, but the complexities of impacts with anisotropic composites remain difficult to investigate computationally. Using meshless finite element analysis methods, the following work quantifies differences between such isotropic approaches and reports on the use of micro-scale modeling to analyze hypervelocity impacts with advanced space composites. Nomenclature A1, B1 = strain rate hardening parameters A2, B2 = pressure and temperature dependence of shear modulus C = strain hardening coefficient C0 = speed of sound E = Young's modulus ℎ , = hardening and tangent modulus G = shear modulus S1-3 = slope coefficients T * = normalized temperature Troom = room temperature Tmelt = melting temperature a = first order volume correction to 0 e = specific internal energy m = thermal softening power exponent n = strain hardening power exponent 0 = Gruneisen gamma εp = equivalent plastic strain ̇ = equivalent plastic stain rate σ = equivalent stress response σy = yield stress σp = effective plastic stress σt = thermally activated plastic stress ρ = density µ = 0 ⁄ -1 β,n = work-hardening parameters

The increased frequency of exploration into space has caused a dramatic rise in the density of debris in orbit. Orbital debris, both natural and man-made, poses an extreme impact risk to satellites and spacecraft. The relative velocities between orbital components and debris can exceed thousands of meters per second, giving rise to immense kinetic energies even for small objects. In such a hypervelocity impact event, the shock pressures exceed the strength of common aerospace materials, and brief shock-induced temperature rises cause melting and vaporization of most structural bodies. Under these extreme conditions, the failure and deformation of solids can resemble fluid flow. By using meshless Lagrangian models in an explicit computational framework, this work identifies analogous fluidic interactions and further quantifies the role of shear and inertial forces in hypervelocity impacts (HVI).