Session: 03-05-01: 8th Symposium on Fastening and Joining Research and Advanced Technology

Paper Number: 116762

116762 - Fastenerless Joining of Carbon Fiber Reinforced Thermoplastic Composite to Aluminum 

The aerospace and automotive applications are adopting fiber reinforced polymer composites in a significant way due to lightweight and energy efficiency benefits. Despite the growing use of composites, metals are still indispensable in many of these applications due to conservative designs and major available manufacturing infrastructure. Hence, there is a major emphasis on hybrid metal-composite designs. Predominantly mechanical joining using fasteners like bolts, rivets, and screws was employed for joining dissimilar materials. Even though it offers firm reliable joints but these fasteners put additional weight on the overall structure hampering the lightweighting purpose. To overcome this challenge adhesive bonding is preferred over joining with fasteners.  Adhesive joining has many advantages including uniform load transfer, corrosion prevention, etc. However, it suffers from a few drawbacks like peel damage, and weathering inhibiting their widespread applicability. This creates an opportunity for the exploration of novel ways of joining dissimilar materials.

In the present work, a novel technique of mechanical interlocking inspired by Japanese wood joining craft is introduced for joining carbon fiber reinforced composite (CFRP) with 6061 aluminum. Different interlocking designs were developed in the form of male and female components. The samples were obtained through waterjet cutting of a 6 mm thick plate of composite and 6061 aluminum. To minimize the influence of the directionality of fibers on the strength, the composite plate was manufactured through an extrusion compression molding process using long fiber thermoplastic pellets of 30 percent carbon fiber polyamide 6. The joint was realized by force fitting of male component into the female component. The performance of these interlocking designs was compared under quasi-static loading condition and their failure modes were analyzed. Further, the effect of material as a male/female component on joint strength was studied. It was observed that composite as a male and metal as a female composition resulted in higher joint strength compared to vice versa. The ultimate tensile strength from the present design(s) is about 145 MPa which is 326% higher than the adhesive joint and it failed due to a fracture of CFRP.  The work is supported by finite element modeling (FEM). The paper will provide a detailed experimental design setup and test results in conjunction with failure modes. Also, it will provide a limited amount of FEM results to provide insight into developed stress in joint structure.

The main advantage the above-mentioned joining technique would offer is the continuity of the joint structure with joining elements which is not the case with lap joining. Lap joining introduces the issue of load eccentricity causing the development of complex stress around the joint structure. This makes the premature failure of the joint. The potential application area for the proposed method could be the joining of multi-material body coverings in an automobile. The innovative designs eliminate/minimize the use of adhesives and fasteners, yet provide superior strength and joint performance. This work was funded by the National Science Foundation (NSF) IUCRC on Composite Hybrid Materials Interfacing (CHMI).

Presenting Author: Akash Phadatare University of Tennessee, Knoxville

Presenting Author Biography: A second-year Ph.D. student in the Mechanical Engineering department at the University of Tennessee, Knoxville. Currently, I am working on a project for the joining of carbon fiber reinforced composite with aluminum. I completed my bachelor's in Fibers and Textile Processing Technology from the Institute of Chemical Technology, Mumbai, India.

Authors:

Akash Phadatare University of Tennessee, Knoxville
Eonyeon Jo University of Tennessee, Knoxville
Deepak Pokkalla Oak Ridge National Laboratory
Seokpum Kim Oak Ridge National Laboratory
Uday Vaidya University of Tennessee, Knoxville