Interface geometry-induced strain distribution in multi-material polyjet fabricates

Interfacial geometry is widely proposed to enhance mechanical reliability in multi-material PolyJet parts, yet the underlying mechanisms governing strain redistribution remain unclear for digital materials. This study systematically investigates three distinct interface designs such as Straight, Interlocked and T-shape with identical nominal contact area across three material pairs (70A–95A, 85A–95A, and 70A–85A) under uniaxial tension. Load–displacement behavior is correlated with full-field surface strain measurements from digital image correlation (DIC) to quantify phase-wise strain partitioning using top and bottom regions of interest (ROIs). To enable interface-level comparison under deformations, an equivalent strain interface is extracted from the strain field using Otsu’s criterion, and the normal strain gradient across this interface is analyzed. Results demonstrate that geometry-induced changes in load-transfer behavior are most pronounced for the high-stiffness 85A–95A pair, whereas combinations involving the compliant 70A phase exhibit increased strain heterogeneity and limited sensitivity to interface geometry. Strain-gradient analysis reveals that stiffness mismatch predominantly governs strain gradient magnitude, whereas interface geometry dictates the spatial localization pattern of load transfer. These findings provide quantitative guidance for geometry–material co-design in multi-material PolyJet fabrication, offering insights into interface optimization for improved load-transfer behavior within the elastic regime.