Study of the optical, thermal, morphological and mechanical characteristics of a laser weldable fiber reinforced polymer

Abstract

AbstractIn recent years, varied industrial users such as the automotive and electronic manufacturers, have greatly expanded the application of technical polymers, exploring the lower weight, improved moldability of complex parts and good mechanical performance that these materials can provide, especially when reinforced with fibers. Among these materials, polybutylene terephthalate reinforced with 30% glass fiber, designated as PBT GF30, is highly interesting, since it combines excellent mechanical properties with watertightness, allowing PBT GF30 to be used in the encapsulation of sensitive electronic elements. However, to maintain access, PBT GF30 products always require the use of joints, which are often created using laser welding. This work presents a detailed characterization of the thermal, optical, mechanical, and morphological characteristics of PBT‐GF30 suitable for laser welding, supported by a numerical analysis. This process allowed to determine the influence of thermal energy on the behavior of the material and thus fully understand the mechanical response of the material after laser welding. Testing of the PBT GF30 in the as received state confirmed a fusion temperature of 225°C and large energy absorption for wavelengths around 1000 nm. Exposure to large temperatures leads to increased fiber exposure and matrix degradation, with a deleterious effect on the mechanical properties. When treated at the highest temperature under consideration, the material exhibited a reduction of 66% in its ultimate tensile stress, 67% in the yield at failure, 45% in the Young's modulus and 44% in the stress intensity factor. Hardness was less affected by the temperature increase. From the numerical model for the tensile and the compact tension tests, it was possible to find a good degree of convergence. This material was generally found suitable for laser welding processes and the determined useful to support the modeling the behavior of laser welded joints.