Quality Analysis of Weld-Line Defects in Carbon Fibre Reinforced Sheet Moulding Compounds by Automated Eddy Current Scanning

Abstract

Discontinuous fibre reinforced composites enable the manufacture of integrated structural components via the complex flow process of compression moulding. However, such processes can lead to the formation of detrimental weld-lines. Here, the meso-structure of carbon fibre sheet moulding compounds (C-SMC) was analysed using conventional non-destructive techniques and automated eddy current (EC) scanning, as well as destructive methods, in an attempt to identify defects such as weld-lines in this class of materials. Compression-moulded plaques with forced weld-lines in two different configurations (adjacent and opposing flow joints) were analysed, showing up to 80% strength reduction versus a defect-free plaque. The EC-determined local fibre orientation and elucidated local microstructure matched those obtained using conventional techniques, showing a dramatic fibre tow alignment parallel to the weld-lines. It was found that failure occurred in proximity to the “non-uniformity” defect regions identified by EC analyses, demonstrating the use of robot-guided EC for successful defect detection in C-SMC structures.

Weld‐lines and its strength evaluation in injection molded parts: A review

“…The variation in the properties depends on many different parameters. Which involves a degree of molecular interdiffusion, anisotropy, material type, type of reinforcement, process parameters, design of the part, etc 15,21,22 …”

“…Which involves a degree of molecular interdiffusion, anisotropy, material type, type of reinforcement, process parameters, design of the part, etc. 15,21,22 When fountain flow-fronts strike each other the mixing or interdiffusion takes place. 1,2 The characteristics of the interdiffusion area depend on viscosity, velocity, meld flow rate, temperature, and pressure of polymeric melt.…”