Browsing by Author "Gokhale, Vaibhav V."

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    Design of a helmet with an advanced layered composite for energy dissipation using a multi-material compliant mechanism synthesis
    (2016) Gokhale, Vaibhav V.; Tovar, Andres; Nematollahi, Khosrow; Zhu, Likun; Chen, Jie
    Traumatic Brain Injuries (TBI) are one of the most apprehensive issues today. In recent years a lot of research has been done for reducing the risk of TBI, but no concrete solution exists yet. Helmets are one of the protective devices that are used to prevent human beings from mild TBI. For many years some kind of foam has been used in helmets for energy absorption. But, in recent years non-traditional solutions other than foam are being explored by different groups. Focus of this thesis is to develop a completely new concept of energy absorption for helmet liner by diverting the impact forces in radial directions normal to the direction of impact. This work presents a new design of an advanced layered composite (ALC) for energy dissipation through action of a 3D array of compliant mechanisms. The ALC works by diverting incoming forces in multiple radial directions and also has design provisions for reducing rotational forces. Design of compliant mechanism is optimized using multi-material topology optimization algorithm considering rigid and flexible material phases together with void. The design proposed here needs to be manufactured using the advanced polyjet printing additive manufacturing process. A general and parametric design procedure is explained which can be used to produce variants of the designs for different impact conditions and different applications. Performance of the designed ALC is examined through a benchmark example in which a comparison is made between the ALC and the traditional liner foam. An impact test is carried out in this benchmark example using dynamic Finite Element Analysis in LS DYNA. The comparison parameters under consideration are gradualness of energy absorption and peak linear force transmitted from the ALC to the body in contact with it. The design in this article is done particularly for the use in sports helmets. However, the ALC may find applications in other energy absorbing structures such as vehicle crashworthy components and protective gears. The ultimate goal of this research is to provide a novel design of energy absorbing structure which reduces the risk of head injury when the helmet is worn.
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    Design of an Advanced Layered Composite for Energy Dissipation using a 3D-Lattice of Micro Compliant Mechanism
    (SAE, 2016-04) Gokhale, Vaibhav V.; Marko, Carl; Alam, Tanjimul; Chaudhari, Prathamesh; Tovar, Andres; Mechanical and Energy Engineering, School of Engineering and Technology
    This work introduces a new Advanced Layered Composite (ALC) design that redirects impact load through the action of a lattice of 3D printed micro-compliant mechanisms. The first layer directly comes in contact with the impacting body and its function is to prevent an intrusion of the impacting body and uniformly distribute the impact forces over a large area. This layer can be made from fiber woven composites imbibed in the polymer matrix or from metals. The third layer is to serve a purpose of establishing contact between the protective structure and body to be protected. It can be a cushioning material or a hard metal depending on the application. The second layer is a compliant buffer zone (CBZ) which is sandwiched between two other layers is responsible for the dampening of most of the impact energy. The compliant buffer zone, comprised by the lattice of micro-compliant mechanism, is designed using topology optimization to dynamically respond by distributing localized impact in the normal direction into a distributed load in the radial direction (perpendicular to the normal direction). The compliant buffer zone depicts a large radial deformation in the middle but not on the surface, which only moves in the normal direction. The effect is a significant reduction of the interfacial shear stress with two adjacent layered phases. A low interfacial shear stress translates into a reduced delamination. The ALC’s response to the impact is tested by using dynamic finite element analysis. The proposed ALC design is intended to be used for the design of protective devices such as helmets and crashworthy components in vehicle structures.