Penetration Mechanics of GLARE™ Fiber-Metal Laminates upon Collision with Micrometeoroids

Abstract

The spacecraft designed for long-duration service are susceptible to hypervelocity impacts of micrometeoroids and orbiting space debris. Such impacts on spacecraft structures can cause spacecraft failure and loss of life. In order to adequately protect the spacecraft bulkhead and flight critical systems, many high-strength composite materials have been developed for debris bumper. GLAss fiber REinforced aluminum is one of the high-performance composites. The review of articles, however, yielded no single study, which has been dedicated to interrogate the damage mechanics of GLAss fiber REinforced aluminum upon collision with micrometeoroids. This study, therefore, aimed at the numerical investigation of penetration phenomena of thick GLAss fiber REinforced aluminum 5-6/5-0.4 laminates upon hypervelocity impact of a projectile. The numerical study employed a predictive model that merged the smoothed particle hydrodynamics and the finite element methods. The model could predict the colossal damage modes of GLAss fiber REinforced aluminum. As seen, the normal impact of a 2 mm diameter spherical 2024-T3 aluminum projectile on GLAss fiber REinforced aluminum, at a relative velocity of 7.11 km/s, resulted into membrane stretching and fiber failure of the glass fiber reinforced epoxy composite laminates. By contrast, the aluminum layers experienced an enormous strain-rate and consequently, suffered thinning, fracture and large mass erosion. The perpetual release waves fragmented the projectile and dispersed the projectile mass prior to the further penetration of GLAss fiber REinforced aluminum. To verify the accuracy of the numerical model, experiments had been conducted by using a two-stage light-gas gun. The experiments generated damage modes of GLAss fiber REinforced aluminum in good correspondence to that of the predictive model. Yet, disparity between the estimations of experiments and simulations had been apparent, which is anticipated due to the phase change of material had not been accounted for in the analysis.

Appendix

Material Model of Al

The semi-empirical flow stress model of Steinberg–Guinan delineated the strain-rate dependent plasticity of Al layers (see Table 2). The model assumed that at a strain-rate of 10⁵ s⁻¹, the yield stress reached the limiting maximum and next, was independent of strain-rate. A shear modulus, proportional to pressure and inversely proportional to temperature, made sure the Bauschinger effect was included in the model. The shear modulus (G) and the yield stress (Y) read:

$$G = G_{0} \left\{ {1 + \left( {\frac{{G^{\prime}_{p} }}{{G_{0} }}} \right)\frac{p}{{\eta^{{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}}} }} + \left( {\frac{{G^{\prime}_{T} }}{{G_{0} }}} \right)\left( {T - 300} \right)} \right\}$$

(7)

$$Y = Y_{0} \left\{ {1 + \left( {\frac{{Y^{\prime}_{p} }}{{Y_{0} }}} \right)\frac{p}{{\eta^{{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}}} }} + \left( {\frac{{G^{\prime}_{\tau } }}{{G_{0} }}} \right)\left( {T - 300} \right)} \right\}\left( {1 + \beta \varepsilon } \right)^{n}$$

(8)

$${\text{subject to}}\,\,\,\,\,\,Y_{0} \left[ {1 + \beta \varepsilon } \right]^{n} \le Y_{\max }$$

where ɛ, β, n, T, η = v₀/v stand for the effective plastic strain, hardening constant, hardening exponent (see Table 2), temperature, and compression, respectively. The subscripts p and T of primed parameters stand for the derivatives at the reference pressure and temperature (T = 300 K, P = 0, ɛ = 0). Subscripts max and zero indicate the maximum value and the reference state before the nucleation of a shockwave. The Mie-Grüneisen equation of state correlated the pressure with the volumetric strain of Al. Material constants, C1 specified the characteristic sound speed in 2024-T3 aluminum alloy and S1 yielded the slope between the shockwave velocity and the particle velocity (see Table 2). Al-elements failed when met the failure strain (see Table 2) in the three normal and the three shear directions.