Advanced Manufacturing

Interlaminar Reinforcement with Polymer Additive Manufacturing – Enhancing Fracture Toughness and Strength

Interfaces in polymer-based fiber reinforced composites are critical regions that are most susceptible to delamination under static and impact loads. Mechanical responses, like compression, bending, impact and combinatory loading on layered composites are affected by interface strength and toughness, geometry and the extent of loading. Debonding or delamination is observed to be a dominant failure mechanism in layered composites and is often accompanied by significant visible damage and reduction in mechanical properties. Thus, interface design is very critical for layered materials, like fiber reinforced composites, and structures like bonded joints, and an effort towards developing smart designing techniques to minimize the damage and failure incurred by weak interfaces has been a focus area in my lab.

Within this work, interfaces are engineered using mechanics information about crack propagation. Utilizing the concept of crack turning, we have achieved enhanced toughness at the interlaminar regions. A combination of computational modeling, additive manufacturing technology like fused filament fabrication (FFF) and experimental validation is used for enabling novel designs at these interfaces to obtain stronger composites that are less susceptible to interface failure. We introduce interface patterns by printing on fiber reinforced prepregs such that they form interlocking patterns. This causes cracks to steer around these patterns causing the interlaminar fracture toughness to increase.

Electron Beam Melting Process Modeling of Nickel Superalloys

Computational modeling of residual stress formation during the electron beam melting process for Inconel 718 8 [In collaboration with Oak Ridge National Lab]: We developed a computational modeling approach to simulate residual stress formation during electron beam melting (EBM) additive manufacturing (AM) process for Inconel 718. The EBM process has demonstrated a high potential to fabricate components with complex geometries, but the resulting components are influenced by the thermal cycles observed during the manufacturing process. High temperatures when combined with substrate adherence during printing can result in warping of the base plate and affect quality of the final component by causing defects. Here, we elucidate the impact of thermal loading on the thermo-mechanical response of the entire system occurring during the EBM process.

Curing Process Modeling of Textile Composites

Textile composites have shown promising capabilities for light-weight and high strength applications. The geometry of the yarns present within these composites is extremely complex, and a thorough understanding of the influence of the manufacturing process on the final composite is very important to determine the overall quality of the composite.

High fidelity computational models have been developed to determine optimum manufacturing parameters, like curing temperature profile, compaction pressure, cure duration, etc. for textile composites. Network formation material model to simulate the curing process accompanied by material degradation due to stress induced microcrack formation within the polymer matrix in the presence of fibers is developed. The computational framework has the potential to be used by composite manufacturers to determine the optimum compaction on dry fabric and curing temperature cycles, and subsequently predict the damage caused during the curing process.

M. Islam and P. Prabhakar, “Computational Modeling of Curing Induced Damage due to Compaction on Woven Fabric Composite,” in ASC 29th Technical Conference, 16th US-Japan Conference on Composite Materials, & ASTM D30 50th Anniversary meeting, UC San Diego, La Jolla, CA, 2014. [Best student paper award].