Investigation on insertion mechanism of ultrasound guided insertion process based on numerical simulation

Abstract

The insertion of finer Z‐pins is the key factor for increasing the reinforcement effects of Z‐pinned composite laminates. This paper presents a three‐dimensional cohesive zone finite element (FE) model for revealing the insertion mechanism of the ultrasound guided insertion process of fine Z‐pins. The prepreg fracture is modeled based on the cohesive elements, where fracture toughness is obtained from the double insertion method. The contact between the needle and prepreg is simulated by LuGre dynamic friction model. According to model simulation and relevant experiments, compared with nonvibratory insertion, smaller insertion force, earlier surface fracture and slighter ply crimp can be observed in the ultrasound guided insertion process. In addition, the prepreg forms an initial crack firstly after needle insertion, followed by a final crack due to needle extraction and prepreg springback. The effects of needle diameter on the insertion force and crack length are discussed. It can be concluded that larger needle diameter can lead to greater insertion force and initial crack length, but has little effect on the final crack length.

Enhancing the Robustness of Hybrid Metal-Composite Connections through 3D printed Micro Penetrative Anchors

“…The insertion of additively manufactured 3D pins into a composite substrate can lead to defects such as in-plane ber crimping and the formation of resin-rich regions [23,18], similar to those encountered in z-pinning, which is an established technique in the eld of composite materials [24,25]; these defects are localized in a limited region surrounding the pin, impacting the original ber-polymer distribution and locally affect the mechanical properties of the substrate [26,27]. Reducing the diameter of the z-pin in the range of 0.3 mm ÷ 0.5 mm has been proven to provide a strategic pathway to mitigate those defects, as suggested by several recent researches [28][29][30]. To date, proposed LPBF AM 3D pins are mainly cylindrical [13,14,26,31], with a diameter in the range of 1.00 mm ÷ 1.5 mm [13-15, 26, 31, 32].…”