Perpustakaan Digital ITB

Composite materials are widely used in lightweight structural applications because of their high sti!ness and strength-to-weight ratio. However, predicting their nonlinear progressive damage remains challenging due to interacting mechanisms across length scales, including matrix plasticity, fiber–matrix debonding, transverse cracking, and interlaminar delamination. This dissertation develops a Direct FE2 multiscale framework to predict the progressive damage behavior of thermoplastic glass-fiber-reinforced impact polypropylene composites. First, the role of unit-cell configuration in transverse cracking is investigated, showing that inter-fiber spacing and fiber arrangement strongly influence damage initiation, growth, and energy dissipation beyond fiber volume fraction alone. Then, the strain-rate dependence of the impact-modified polypropylene matrix is incorporated through a Johnson–Cook-type formulation. Finally, the framework is applied to micro-three-point bending under quasi-static and low-velocity impact loading, successfully reproducing the experimental response and damage sequence of transverse cracking followed by interlaminar delamination.