Abstract
This paper presents the effect of through-thickness reinforcement by steel z-pins on the interlaminar shear properties and strengthening mechanisms of carbon fiber reinforced aluminum matrix composites (Cf/Al) with a short beam shear test method. Microstructural analysis reveals that z-pins cause minor microstructural damage including to fiber waviness and aluminum-rich regions, and interface reaction causes a strong interface between the stainless steel pin and the aluminum matrix. Z-pinned Cf/Al composites show reduced apparent interlaminar shear strength due to a change in the failure mode compared to unpinned specimens. The changed failure mode could result from decreased flexural strength due to microstructural damage as well as increased actual interlaminar shear strength. Fracture work is improved significantly with a z-pin diameter. The strong interface allows the deformation resistance of the steel pin to contribute to the crack bridging forces, which greatly enhances the interlaminar shear properties.
Highlights
Carbon fiber reinforced aluminum matrix composites (Cf/Al) have increasingly been used for a variety of automotive and aerospace applications because of their high specific modulus, high specific strength, high thermal conductivity, and low coefficient of thermal expansion [1,2,3,4,5]
Many studies [6,7,8,9,10] have demonstrated that z-pins can improve the delamination fracture toughness, interlaminar shear strength, impact damage tolerance, and delamination fatigue resistance of composites. z-pins are effective at increasing the ultimate strength, fatigue performance, and damage tolerance of bonded composite joints [11,12,13]
During the sample preform preparation phase, the z-pin squeezed the surrounding carbon fibers and a void around the z-pin was left; this gap was filled by AI at a later stage of melt Al being poured into the preform
Summary
Carbon fiber reinforced aluminum matrix composites (Cf/Al) have increasingly been used for a variety of automotive and aerospace applications because of their high specific modulus, high specific strength, high thermal conductivity, and low coefficient of thermal expansion [1,2,3,4,5]. Delamination cracks cause relatively low interlaminar properties of Cf/AI composites, despite their excellent in-plane mechanical properties. It is significantly crucial to improve the interlaminar shear properties of Cf/AI composites for their future applications. The z-pinning method has been advocated as a simple and effective method to enhance the delamination resistance of composites [6,7,8]. Many studies [6,7,8,9,10] have demonstrated that z-pins can improve the delamination fracture toughness, interlaminar shear strength, impact damage tolerance, and delamination fatigue resistance of composites. Z-pins are effective at increasing the ultimate strength, fatigue performance, and damage tolerance of bonded composite joints [11,12,13] Many studies [6,7,8,9,10] have demonstrated that z-pins can improve the delamination fracture toughness, interlaminar shear strength, impact damage tolerance, and delamination fatigue resistance of composites. z-pins are effective at increasing the ultimate strength, fatigue performance, and damage tolerance of bonded composite joints [11,12,13]
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