Morteza Kiani

This paper presents a high accuracy Finite Element approach for delamination modelling in laminated composite structures. This approach uses multi-layered shell element and cohesive zone modelling to handle the mechanical properties and damages characteristics of a laminated composite plate under low velocity impact. Both intralaminar and interlaminar failure modes, which are usually observed in laminated composite materials under impact loading, were addressed. The detail of modelling, energy absorption mechanisms, and comparison of simulation results with experimental test data were discussed in detail. The presented approach was applied for various models and simulation time was found remarkably inexpensive. In addition, the results were found to be in good agreement with the corresponding results of experimental data. Considering simulation time and results accuracy, this approach addresses an efficient technique for delamination modelling, and it could be followed by other researchers for damage analysis of laminated composite material structures subjected to dynamic impact loading

A vehicle–dummy multidisciplinary design optimization problem is treated as a multilevel system composed of structural and occupant restraint system design elements. The vehicle-based responses and the dummy-based responses are obtained from nonlinear transient dynamic finite element simulations of full frontal impacts and side impacts. The wall thicknesses of a set of energy-absorbing components together with the occupant restraint system control parameters associated with the seat belt and the airbag are treated as design variables and used to optimize the multilevel system to minimize both the structural mass and the selected injury criteria. Each element optimization problem is modeled using the augmented Lagrangian with exponential penalty function formulation. A single-loop coordination strategy is used to solve the multilevel optimization problem. To maximize the computational efficiency, surrogate models are used to approximate the vehicle-based responses and the dummy-based responses. The results of the vehicle–dummy design problem are used to examine the computational efficiency and the accuracy of the decomposed multilevel optimization methodology.

Car body design in view of structural performance and lightweighting is a challenging task due to all the performance targets that must be satisfied such as vehicle safety and ride quality. In this paper, material replacement along with multidisciplinary design optimization strategy is proposed to develop a lightweight car body structure that satisfies the crash and vibration criteria while minimizing weight. Through finite element simulations, full frontal, offset frontal, and side crashes of a full car model are evaluated for peak acceleration, intrusion distance, and the internal energy absorbed by the structural parts. In addition, the first three fundamental natural frequencies are combined with the crash metrics to form the design constraints. The wall thicknesses of twenty-two parts are considered as the design variables. Latin Hypercube Sampling is used to sample the design space, while Radial Basis Function methodology is used to develop surrogate models for the selected crash responses at multiple sites as well as the first three fundamental natural frequencies. A nonlinear surrogate-based optimization problem is formulated for mass minimization under crash and vibration constraints. Using Sequential Quadratic Programming, the design optimization problem is solved with the results verified by finite element simulations. The performance of the optimum design with magnesium parts shows significant weight reduction and better performance compared to the baseline design.

Accurate simulation of the composite material crash tubes subjected to axial impact is a challenging field of study in automotive or aerospace industry; however, analytical prediction of the crashworthiness behavior in composite materials is limited. In this paper, three different analytical approaches are presented which have been used to study the crashworthiness of a pultruded glass-polyester tube. The first model is established based on the single shell elements. This approach is very effective, when composite part is assembled in the full structure. However, this technique can be used when the experimental result is available. In the second approach, the crash tube is modeled by using multi-layered shell element (delamination model). Relying on coupon test information of the composite material, this modeling technique can provide reasonable result for the energy absorption of the tube. The third modeling approach is looking for crashworthiness prediction of the discussed tube by using the first model which its parameters are tuned based on the result of the second model. Finally, the sensitivity of the result is studied by changing the major parameters in the first model. This paper is looking for finding a method to reasonably estimate the crashworthiness behavior in the composite materials.

The traditional crashworthiness optimisation problem is augmented by inclusion of additional design criterion associated with vehicle vibration characteristics. Through finite element (FE) simulations, full frontal, offset frontal and side crashes of a full vehicle model are analysed for peak acceleration, intrusion distance and internal energy. Moreover, the FE crash model of the vehicle is modified to develop a vibration-analysis model for evaluation of natural frequencies and mode shapes. Design of computer experiments through Latin hypercube sampling is used to sample the design space defined by the wall thicknesses of 22 parts. Radial basis functions are used to generate separate surrogate models for the selected crash responses measured at multiple sites as well as the fundamental natural frequencies in bending and torsion. A nonlinear surrogate-based mass minimisation problem is formulated and solved under crash and vibration constraints with the results verified through FE simulations. The optimum vehicle design under multiple design criteria is presented and the vehicle's characteristics are compared with those of the baseline design as well as those associated with the optimum design based on crash responses alone.