Abstract
Composite joining typically involves multiple steps, such as drilling and surface treatment, as part of the manufacturing process, which leads to low throughput and long cycle times. In the present study, we demonstrated a macro-level mechanical interlocking (MI) based, rapid joining technique to assemble additively manufactured compression molded (AMCM) panels, enabling the production of parts larger than the mold dimensions. Composite panels made of 20 wt% short carbon fiber reinforced acrylonitrile butadiene styrene (CF/ABS) were joined using MI features of various geometries, namely tree (TR), dovetail (Dov), rectangle 2 (Rect2), and rectangle 1 (Rect1), and their in-plane strength was evaluated. The resultant strength of the tested MI joints reached up to 74 % of the baseline tensile strength (i.e., the ‘no joint’ case). Observations from optical and scanning electron microscopy revealed inadequate polymer diffusion between the adherends, indicating that the joint strength was primarily derived from mechanical interlocking. Additionally, the fracture surfaces exhibited stress-whitening marks, which were characterized using differential scanning calorimetry (DSC). The increase in melting enthalpy suggested local stretching of polymer chains due to MI. Finite element analysis (FEA) indicated that the Rect1 MI feature, which generated the lowest stress concentration, outperformed the others in terms of joint strength, achieving 42 MPa. As a demonstration of the MI joining method, a battery box tray measuring 108 cm × 34 cm using a mold with an effective dimension of 36 cm × 34 cm successfully manufactured, resulting in a part with an area three times larger than the mold. This study presents a promising approach to improving composite joining techniques while minimizing production complexities.
| Original language | English |
|---|---|
| Article number | 112851 |
| Journal | Composites Part B: Engineering |
| Volume | 306 |
| DOIs | |
| State | Published - Nov 1 2025 |
Funding
In the case of MI joints, the apparent joint strength is primarily derived from the resistance introduced by the interlocking feature, which restrains the relative displacement or separation of the joined parts prior to plastic deformation of the adherends [17,19]. MI also aids in the predictable failure behavior of the joint. In the present study, MI-based joints achieved up to 74 % of the strength of the baseline (no-joint) condition, as observed in the Rect1 joint. The introduction of MI into a step joint configuration resulted in a remarkable increase of up to 428 % in joint strength. An ascending trend in joint strength was observed across the tested MI joints, sequenced as TR, Dov, Rect2, and Rect1 (see Fig. 7). This trend can be attributed to each feature's ability to distribute stress more uniformly across the joining area and to constrain relative movement between the adherends. These findings were further supported by FEA simulations and DIC strain measurements (see Fig. 9). All the joint specimens failed at stress concentration zones developed close to the joint boundary.The authors gratefully acknowledge support from the Composite Core Program (CCP 2.0), supported by Vehicle Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy. Portion of the research were sponsored by Advanced Materials and Manufacturing Technology Office, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. The authors extend their gratitude to Jaydeep Kolape, Manager at Advanced Microscopy and Imaging Center for providing assistance in optical and scanning electron microscope imaging. The authors also wish to thank Komal Chawala, Postdoc at ORNL, for her support with the fiber orientation tensor measurement work. The authors gratefully acknowledge the Institute of Advanced Composites Manufacturing Innovation (IACMI). Additionally, authors want to thank National Science Foundation (NSF), Industry University Cooperative Research Center (IUCRC) under grant number NSF-2052738 for offering technical assistance and resources. The authors gratefully acknowledge the Institute of Advanced Composites Manufacturing Innovation (IACMI) . Additionally, authors want to thank National Science Foundation (NSF) , Industry University Cooperative Research Center (IUCRC) under grant number NSF-2052738 for offering technical assistance and resources. The authors gratefully acknowledge support from the Composite Core Program (CCP 2.0), supported by Vehicle Technologies Office , Office of Energy Efficiency and Renewable Energy , U.S. Department of Energy . Portion of the research were sponsored by Advanced Materials and Manufacturing Technology Office , under contract DE-AC05-00OR22725 with UT-Battelle, LLC . The authors extend their gratitude to Jaydeep Kolape, Manager at Advanced Microscopy and Imaging Center for providing assistance in optical and scanning electron microscope imaging. The authors also wish to thank Komal Chawala, Postdoc at ORNL, for her support with the fiber orientation tensor measurement work.
Keywords
- In-plane joining
- Joint strength
- Mechanical interlocking (MI)
- Seamless joining
- Thermoplastic composite joining