Huang, Ningwei2026-03-272026-03-272026-03-272026-03-26https://hdl.handle.net/10012/22981Growing concerns regarding climate change have prompted national and international regulatory agencies to implement increasingly strict regulations aimed at reducing carbon dioxide (CO₂) emissions. These regulations have driven automotive manufacturers to place greater emphasis on sustainability and improved fuel efficiency in vehicle development. Owing to their high specific strength and stiffness, and superior energy absorption capability, carbon fiber-reinforced plastic (CFRP) composites are considered promising lightweight materials for vehicle frontal crash structures. Their widespread adoption in the automotive industry was previously limited due to high manufacturing costs and challenges in accurately predicting their response under impact loading. However, CFRP components manufactured via high-pressure resin transfer (HP-RTM) with highly reactive resins enable reduced production cycle times and, thus, adoption in automotive structures. Unidirectional non-crimp fabric (UD-NCF) reinforcements offer further advantages, including reduced manufacturing costs, high in-plane mechanical properties, and enhanced design flexibility. To meet safety requirements, vehicle structures must be designed to effectively absorb energy under various impact conditions to protect the occupants from injury. Previous studies have primarily focused on evaluating the impact performance and energy absorption characteristics of CFRP composite components under axial loading. Few studies have investigated the effects of oblique loading on the crush performance of composite structures and they are mainly restricted to closed-profile tubes, which are difficult to manufacture using liquid composite molding technologies such as HP-RTM. To date, the crush performance of UD-NCF composite components under oblique loading has not been examined. Therefore, this thesis aims to design a UD-NCF composite frontal crush component capable of achieving progressive energy absorption under both axial and 30-degree oblique loading conditions. The design is limited to adhesively bonded double channel components as they can be readily fabricated using HP-RTM processes, while the scope of the study is intended to address several considerations for this design concept. Firstly, the energy absorption capability and failure modes of UD-NCF composite single and double hat channel specimens with [0/±45/90]s and [±45/02]s stacking sequences under quasi-static oblique (i.e., 30-degree off-axis) loading were experimentally investigated to provide data for validation of an impact simulation model. For the single hat channel, specimens with a [0/±45/90]s layup achieved 0.78% higher total energy absorption and 11.2% higher specific energy absorption (SEA) than specimens with a [±45/02]s layup. Specimens with both stacking sequences exhibited lamina bending during the initial crushing stage, followed by premature failure. For the adhesively bonded double hat channel, the [±45/02]s specimens yielded 6.4% higher total energy absorption and 9.95% higher SEA than the [0/±45/90]s specimens due to their higher axial stiffness. The double hat channel configuration demonstrated significant improved crush stability than single hat channels throughout the loading process, regardless of stacking sequences. Secondly, computer-aided engineering (CAE) impact simulation models were developed to predict the energy absorption capability of UD-NCF composite channels under quasi-static and dynamic crushing conditions. Simulation models for both single and double hat channel specimens were validated against the performed oblique crushing experiments and exiting axial crush test data from the literature. The results showed that the CAE impact simulation model accurately predicted the crush performance for both single and double hat channel specimens under dynamic axial loading, while having reduced accuracy under quasi-static loading conditions. Lastly, the influence of channel cross-sectional geometry and laminate stacking sequence on energy absorpiton capacility of the UD-NCF composite channels under dynamic oblique loading was investigated using the validated simlation models. Single and adhesively bonded double channels with five distinct geometries and six stacking sequences were considered in the study. All single channel geometries with a [0/±45/90]s stacking sequence exhibited similar SEA, which was the case for both axial and oblique dynamic loading. Under oblique loading, all double channel geometries with [0/±45/90]s and [0/±45/90/±30]s stacking sequences exhibited premature failure. The hat channel geometry consistently demonstrated stable progressive crushing, whereas the other geometries considered showed greater sensitivity to stacking sequence and loading angle. Across all stacking sequences considered, only channels with a [±45/02]s stacking sequence achieved stable crushing under both axial and oblique loading, while also providing the highest SEA values. The double hat channel with the [±45/02]s stacking sequence was identified as the most promising configuration for subsequent frontal crush structure design. Overall, this represents the first comprehensive assessment of the crush performance of UD-NCF composite components under oblique loading conditions. These findings contribute practical design guidelines for the future development of lightweight UD-NCF frontal crush structures in vehicles.enMaster Thesis