Drop-weight impact studies of glare 5 fiber-metal laminates

Drop-Weight Impact Studies of GLARE 5 Fiber-Metal Laminates

A. Seyed Yaghoubi,Y.X. Liu,

B.M.Liaw

Department of Mechanical Engineering, The City College of New York,

Convent Avenue and 138th Street,New York,NY 10031, USA

ABSTRACT

Impact responses and damage induced by a drop-weight instrument on GLARE 5 fiber-metal laminates with different layup configurations and geometries were studied. The damage characteristics were evaluated using both the nondestructive ultrasonic and mechanical sectioning techniques. Only the contour of entire damage area could be obtained using ultrasonic C-scan whereas more details of damage were provided through the mechanical cross-sectioning technique. It was found that failure mode changed with varying stacking sequence. GLARE 5 made of unidirectional fibers had the worst impact resistance; followed by cross-ply and angle-ply configurations, while the quasi-isotropic lay-up showed the best resistance to impact. Finally, influence of different geometries was considered. The results show that by introducing circular geometry, damage patterns and impact behaviors were changed. This was especially apparent for panels with the quasi-isotropic layup configuration.

INTRODUCTION

GLARE 5 is a fiber–metal laminate (FML) made of alternating layers of 2024-T3 aluminum alloy sheets and S2-glass/epoxy laminates. FMLs combine the beneficial properties of metals and fiber-reinforced polymers, providing superior mechanical properties in comparison with conventional polymer matrix composites or aluminum alloys [1-3]. Liu et al. [4] investigated low velocity impact damage on ARALL 3 and various GLARE grades, i.e., GLARE 1, 2 and 3. They found that GLARE 1 with glass-epoxy prepregs possessed higher impact tolerance than ARALL 3 with aramid-epoxy prepregs. They also concluded that GLARE 3 with [0°/90°] cross-ply glass-epoxy prepregs offered better impact resistance than GLARE 2, which is made of [Ͳଶι] unidirectional glass-epoxy prepregs. Hitchen et al. [5] considered the effect of stacking sequence on impact damage in a carbon fiber-epoxy composite. They concluded that the stacking sequence influenced both the pre- and post-compression strengths and affected the impact damage in 16-ply carbon fiber toughened epoxy laminates. They also reported that the total delamination area was a function of the stacking sequence. Choi et al. [6] concluded that ply orientation and stacking sequence could significantly affect impact damage. They also found that impact damage was more sensitive to the change of stacking sequence than of thickness. The influence of lay-up configuration on graphite-epoxy composite material was studied by Guynn et al. [7]. They concluded that the difference in compression failure strain due to stacking sequence were small. Cantwell [8] studied geometrical effects in the low velocity impact response of GFRP. He drew a conclusion that tests on a range of circular and square plates had shown that the degree of damage within the structure was related to the force generated during the impact event.

In this study, the effect of stacking sequence and geometry were considered to evaluate the low velocity impact behavior of the GLARE 5 composite materials through drop weight tests. Optical imaging, ultrasonic C-scan and mechanical sectioning techniques were used to assess the impact damages.

EXPERIMENTAL PROCEDURES

All GLARE panels considered in this study consist of 2024-T3 aluminum alloy with a thickness of 0.305mm (0.012”) per layer and S2-glass/epoxy laminated layers, each with a thickness of 0.508 mm (0.020”). Each S2-glass/epoxy layer has a layup orientation according to Table 1.Panels were cut into two different geometrical shapes: square and circular, with T. Proulx (ed.), Experimental and Applied Mechanics, Volume 6, Conference Proceedings of the Society for Experimental267 Mechanics Series 9999, DOI 10.1007/978-1-4614-0222-0_33, © The Society for Experimental Mechanics, Inc. 2011