Jafor Md Abu, Sayah Neshat, Smith Douglas E, Stano Gianni, Fleck Trevor J
Department of Mechanical Engineering, Baylor University, Waco, TX 76798, USA.
Department of Mechanical Engineering, Polytechnic University of Bari, 70125 Bari, Italy.
Materials (Basel). 2024 Aug 9;17(16):3953. doi: 10.3390/ma17163953.
Material extrusion (MEX) additive manufacturing has successfully fabricated assembly-free structures composed of different materials processed in the same manufacturing cycle. Materials with different mechanical properties can be employed for the fabrication of bio-inspired structures (i.e., stiff materials connected to soft materials), which are appealing for many fields, such as bio-medical and soft robotics. In the present paper, process parameters and 3D printing strategies are presented to improve the interfacial adhesion between carbon fiber-reinforced nylon (CFPA) and thermoplastic polyurethane (TPU), which are extruded in the same manufacturing cycle using a multi-material MEX setup. To achieve our goal, a double cantilever beam (DCB) test was used to evaluate the mode I fracture toughness. The results show that the application of a heating gun (assembled near the nozzle) provides a statistically significant increase in mean fracture toughness energy from 12.3 kJ/m to 33.4 kJ/m. The underlying mechanism driving this finding was further investigated by quantifying porosity at the multi-material interface using an X-ray computed tomography (CT) system, in addition to quantifying thermal history. The results show that using both bead ironing and the hot air gun during the printing process leads to a reduction of 24% in the average void volume fraction. The findings from the DCB test and X-ray CT analysis agree well with the polymer healing theory, in which an increased thermal history led to an increased fracture toughness at the multi-material interface. Moreover, this study considers the thermal history of each printed layer to correlate the measured debonding energy with results obtained using the reptation theory.
材料挤出（MEX）增材制造已成功制造出在同一制造周期中加工的由不同材料组成的无组装结构。具有不同机械性能的材料可用于制造仿生结构（即硬材料与软材料相连），这在生物医学和软机器人等许多领域都很有吸引力。在本文中，介绍了工艺参数和3D打印策略，以改善在同一制造周期中使用多材料MEX装置挤出的碳纤维增强尼龙（CFPA）和热塑性聚氨酯（TPU）之间的界面附着力。为了实现我们的目标，使用双悬臂梁（DCB）试验来评估I型断裂韧性。结果表明，使用加热枪（安装在喷嘴附近）可使平均断裂韧性能量从12.3 kJ/m显著提高到33.4 kJ/m。除了量化热历史外，还使用X射线计算机断层扫描（CT）系统对多材料界面处的孔隙率进行量化，进一步研究了这一发现背后的潜在机制。结果表明，在打印过程中同时使用熔珠熨烫和热风枪可使平均孔隙体积分数降低24%。DCB试验和X射线CT分析的结果与聚合物愈合理论非常吻合，在该理论中，热历史的增加导致多材料界面处的断裂韧性增加。此外，本研究考虑了每个打印层的热历史，以将测得的松脱能量与使用链段蠕动理论获得的结果相关联。
