Low-Velocity Impact Characteristics of Hybrid Aluminum/CFRP Single Hat Sectioned Beam Adhesively Bonded Using Adhesive Tape

Abstract

Single hat sectioned hybrid beams composed of aluminum and Carbon Fiber Reinforced Polymeric materials (CFRP), intended for structural applications in the automotive and aviation sectors, have been studied from the point of their energy absorption capabilities when submitted to transverse low-velocity impact loading. Carbon fiber-epoxy composite prepregs were placed on the inside of the single hat sectioned aluminum sheet and completely cured in the autoclave under the recommended curing cycle. The bonding process between the aluminum sheet and composite layers was achieved by using 3M VHB™ 4930 double-sided acrylic foam tape. Bonding the aluminum and composite layers through adhesive tape eliminates the requirement of surface preparation of the aluminum layer through chemical etching or mechanical abrasion and thereby the strength of the metallic layer is not reduced due to the formation micropores during the chemical etching process. Results are shown in terms of load-displacement and damage morphologies diagrams; characteristic trends are compared and discussed. It was observed that the presence of viscoelastic adhesive tape material restricts the rupture (visual cracks) failure of the outer aluminum layer, resulting in the only impact-induced indentation for all impact energies. Numerical simulations were also performed to characterize and predict the failure mechanism of such hybrid beams when subjected to impact loading. Numerical predictions showed good correlation with experimental results for all impact histories at low and medium impact energies but a showed slight discrepancy for highest impact energy and were not able to successfully capture the system response in the unloading region. Current modeling does not consider damage healing or recovery with unloading and it is difficult to account for such change in material state. This study provides the low-velocity impact characteristics and collapse behavior of the hybrid hat sectioned beams under tensile and shear forces developed by impact loading by providing insight to their primary damage mechanisms relative to the impact energies. It was found that the primary damage of the specimen’s changes from impact-induced indentation, minimal fiber breakage to partial perforation accompanied by larger indentation depth as the impact energy is increased from 6 to 12 J.