Tighter regulation on CO2 emission poses new technological challenges in automotive industries. Multiple solutions are being sought after, e.g. using alternative fuels, reducing aerodynamic drag, making efficient engine, or utilizing composite materials to make lightweight and recyclable components. However, impact (collision, debris) is inevitable in automotive structures, and attempt to improve impact resistance of composites requires a good understanding of the underlying damage as a prime energy dissipation mechanism. We collaborate with an industrial partner to study the newly-developed continuous E-glass fiber-reinforced polypropylene thermoplastic composites (GFPP). We performed a multidisciplinary approach to develop novel experimental approach and numerical models in order to streamline the design of structural thermoplastic composites with excellent impact properties. To study the damage mechanism, we performed quasi-static indentation (QSI), a commonly-used test to represent impact albeit its low speed (1.25 mm/min), and low-velocity impact (LVI) test (impactor velocity range: 2-4 m/s) using a standard drop tower (Instron CEAST 9350). Unlike the classical understanding in literature, we found that matrix behavior (ductility, toughness) changes the damage mechanism of GFPP under QSI and impact, which limits the applicability of QSI. To achieve an in-depth understanding of damage, we also performed an in situ mechanical test on GFPP inside the scanning electron microscope (SEM) where we could track the crack initiation, propagation and interaction between damage modes at microscale (fiber-matrix levels). To complete the studies, we developed finite element micromechanical model to simulate damage and failure of GFPP at microscale. This model successfully reveals the most dominating factor in the failure of composite at microscale: inter-fiber distance.
Dr. Arief Yudhanto joined KAUST in 2014 as a postdoctoral research fellow at COHMAS (Composites Heterogeneous Materials Analysis and Simulation) laboratory lead by Prof. Gilles Lubineau (Mechanical Engineering). At COHMAS, he is leading a research project with an industrial partner on thermoplastic composites. He received his Ph.D. in Aerospace Engineering from Tokyo Metropolitan University (TMU, Japan), M. Eng. in Mechanical Engineering from National University of Singapore (NUS), and B.S. in Aeronautics/Astronautics from Bandung Institute of Technology (ITB, Indonesia). Before joining COHMAS-KAUST, he worked as a researcher at TMU, JAXA (Japan Aerospace Exploration Agency), A*STAR-Data Storage Institute (Singapore) and Hitachi GST (Western Digital).