HVI tests on CFRP laminates at low temperature D. Numata a, * , K. Ohtani b , M. Anyoji a , K. Takayama c , K. Togami d , M. Sun e a Graduate School of Engineering, Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai, Miyagi 980-8577, Japan b Interdisciplinary Shock Wave Research Laboratory, Institute of Fluid Science, Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai, Miyagi 980-8577, Japan c Biomedical Engineering Research Organization, Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai, Miyagi 980-8577, Japan d Nagoya Aerospace Systems Works, Mitsubishi Heavy Industries, LTD.,10 Oye-cho, Minatoku, Nagoya 455-8515, Japan e Center for Interdisciplinary Research, Tohoku University, 6-3, Aramaki aza Aoba, Sendai 980-8578, Japan article info Article history: Available online 5 August 2008 Keywords: Hypervelocity impact Low temperature Space debris bumper shield Composite material abstract The paper reports a result of low temperature hypervelocity impact (HVI) tests of aluminum sphere against a 16-ply quasi-isotropic Carbon Fiber Reinforced Plastic (CFRP) laminate plate at speed ranging from 1.4 to 5.4 km/s in air at 10 Pa. The result was compared with room temperature impacts. At low speed impact on CFRP plates, fracture patterns of specimens varied depending on their temperatures, whereas at high-speed impact, any significant differences in the fracture patterns around penetration holes and independent of the temperatures. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction For man-made space structures for long term in service, their protection from space debris impacts are still one of the most important tasks. In low earth orbit (LEO), space debris sized over 100 mm in diameter can be tracked by the Space Surveillance Network and hence space structures can evade impacts by maneuver. Most of space debris sizes are even smaller than this value and technically unable to be tracked [1]. Impact velocities of space debris in LEO are ranging from 5 to 14 km/s [2] and in average about 10 km/s [3]. Even small debris less than 10 mm in diameter would have enormous kinetic energy and hence their impinge- ments would cause catastrophic damages. For the protection of space structures from space debris impacts, so-called Whipple bumper shield has been intensively used [4] and the optimization of shielding materials and their spacing are still a research task. Among previous laboratory scale HVI tests, most of experiments were performed at room temperature [5–8]. However, when space structures or space vehicles are in the shadow of earth, their surface temperature decreases, due to thermal radiation to the space, down to even 100 K. Material properties of space structure surfaces at such temperature would differ significantly from those at room temperature. However, a limited number of HVI test results at low temperatures [9–12] are reported, in particular, HVI data of composite materials at low temperature, so far as we know, has not been opened yet. The collection of HVI data at cryogenic temper- ature is a purpose of this experiment. We conducted a series of HVI tests by using a ballistic range equipped with a cryogenic test chamber in the Interdisciplinary Shock Wave Research Laboratory (ISWRL) of the Institute of Fluid Science, Tohoku University. The cryogenic test chamber was placed in its 1.66 m diameter and 12 m long recovery section chamber [9] and composite materials (CFRP) were installed in the cryogenic test chamber. Aluminum spheres projected at speeds ranging from 1.4 to 5.4 km/s in air at 10 Pa impinged against composite material plates at low temperature. For observations we used high-speed video recording based on shadowgraph optics. At low speed impact tests, fracture patterns on CFRP plates differ depending on temperatures, whereas at high-speed impact tests, fracture patterns around penetration holes are nearly unvaried and inde- pendent of temperatures. 2. Experimental facility and test conditions 2.1. Ballistic range Fig. 1 shows the ISWRL two-stage light gas gun, which consists of a pump tube of 51 mm in diameter and 3400 mm in length, a launch tube of 15 mm in diameter and 3000 mm in length and a 12 m long and 1.66 m inner diameter recovery chamber made of stainless steel. It has three sets of cross-positioned flash X-ray sources and three sets of 600 mm diameter observation sections, in which 20 mm thick acrylic window is recess mounted by 500 mm from the recovery tank inner surface. This is arranged in order to * Corresponding author. Tel.: þ81 22 217 5285; fax: þ81 22 217 5324. E-mail address: numata@rainbow.ifs.tohoku.ac.jp (D. Numata). Contents lists available at ScienceDirect International Journal of Impact Engineering journal homepage: www.elsevier.com/locate/ijimpeng 0734-743X/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijimpeng.2008.07.055 International Journal of Impact Engineering 35 (2008) 1695–1701