Interfacial fracture properties of environmentally friendly hybrid systems

Excerpt

Hybrid systems consist of alternating layers of metal and fiber-reinforced polymer matrix composites. These systems also referred as composite metal laminates (CML) exhibit excellent resistance to fatigue and impact loading as well as superior specific stiffness and strength [1]. In addition, the residual strength of cracked CMLs has been shown to be greater than that of the plain metal counterpart as a result of crack bridging between the composite and metal constituents [2‐4]. Traditionally, CMLs are based on thermosetting polymer matrices which normally exhibit a brittle deformation behavior and are associated with long manufacturing cycles. In contrast, thermoplastic-based CMLs offer significant advantages, including shorter processing times, high fracture toughness and the possibility of post-impact repair. However, one of the limiting factors for the development of these CMLs is the reduced availability of engineering knowledge related to their fracture mechanisms since laminate properties basically depend on the bi-material interfacial bond strength along with the matrix and reinforcing agent properties [5]. Reyes and Cantwell [6‐9] have reported excellent mechanical and impact properties for polypropylene-based CMLs compared to monolithic aluminum. Here, an amorphous chromate coating surface treatment applied to the aluminum substrates combined with a layer of maleic anhydride modified polypropylene were used to achieve an excellent level of adhesion along the bi-material interface. However, the use of chrome VI that is utilized in such surface treatments has been restricted by the control of major accident hazards (COMAH) as a result of its harmful environmental impact. Therefore, this letter presents the results on the interfacial fracture properties of lightweight composite-metal hybrid systems based on thermoplastic composite materials and aluminum alloy by applying environmentally friendly (non-chromate) surface treatments to the metal substrates. In addition, the affect of varying the number of modified polypropylene interlayers is explored. …