Browse Topic: Unitized bodies and monocoque
The design of the exterior body shape and structure of a solar-electric sports car which competed in the 2019 Bridgestone World Solar Challenge (BWSC) Cruiser Class is explored. A low-drag and low-lift aerodynamic shape with a coefficient of lift near zero and drag area of 0.16 m2 is developed as a primary focus around the constraints of a solar array, occupant space, and aesthetics. The maximally sized 5 m2 rearward tilted solar array capable of generating an expected event average power of 885 W influences the size and shape of the roof. The space for which two occupants are seated in the vehicle is developed to achieve a reclined occupant position that minimizes the vehicle frontal area. A carbon fiber-reinforced polymer (CFRP) and foam composite sandwich monocoque make up the structure of the vehicle at a mass of 59.53 kg. Factors of practicality and their compromises are also explored.
The conceptual design of a full-body composite monocoque chassis has been presented at various student-level racing contests due to its high strength-to-weight ratio and torsional stiffness. However experimental studies to demonstrate the performance of the design are limited. This study aims to find the optimum configuration and number of stacked layers of carbon fiber sandwich panel using finite element analysis (FEA), as well as investigate the mechanical performance of the proposed sandwich configuration by experimentation in order to demonstrate the practical performance of a fully composite monocoque chassis made from the optimized configuration of the sandwich panel. A composite monocoque consisting of five stacked layers of [W45/UD0/W90/UD45/W0/core]symmetry was proposed, where W, UD, and the subscripts indicate woven and unidirectional (UD) carbon fibers and their orientation in the measurement unit of degrees. Three-point bending and perimeter shear tests were conducted on samples of the proposed configuration. The samples exhibited a high flexural rigidity of 2980 Nm2 and a small deformation of 0.99 mm in the perimeter shear test. The maximum deformation from the side impact and impact to the front bulkhead was less than 2.5 mm, which is 10 times less than the maximum allowable deformation specified by Formula SAE (FSAE) rules. A high stress of 25 MPa was generated by the applied load in both tests, but this substantially decreased throughout the chassis, indicating that the stress was mitigated and, consequently, cockpit safety was enhanced. A total weight of 29 kg and torsional stiffness of 3806.23 Nm/deg were achieved. Therefore, our suggested carbon fiber sandwich panel configuration could be implemented, with a high specific modulus and relatively high torsional stiffness, in small-scale racecars or lightweight structures.
This document is a road test procedure for comparing the corrosion resistance of both coated and uncoated sheet steels in an undervehicle deicing salt environment.
This paper summarises the history of Rochdale Motor Panels and Engineering Ltd. (RMP), established in England after the Second World War, from its origins as a small car-repair business though to the manufacture of sports coupés utilising an innovative glass-fibre monocoque construction. The political climate which caused RMP and similar undertakings to develop and flourish in the 1950s and 60s is explained together with details of the three men who had the defining influence on the cars that were created. Products, including aluminium-bodied cars, produced primarily for racing, are described, leading into the introduction of glass-fibre construction which enabled a profitable transition into higher volume body and chassis manufacture, and ultimately completely assembled cars. Particular attention is paid to the ‘GT’ and ‘Olympic’ models, the former being the highest volume variant produced, and the latter a revolutionary sports car which received critical acclaim when compared with products from contemporary high-volume and specialist OEMs. The circumstances leading to the eventual decline of car manufacture and the legacy of the marque on the town of Rochdale, bring the story to a close.
The Curtin Motorsport Team (CMT) currently utilise a 4130 alloy steel space frame chassis for their entry into the Formula SAE-A competition (FSAE). According to SolidWorks models, the current chassis has a weight of 32kg with a torsional stiffness of 744Nm/degree. Although this is an adequate system proven to be cost effective, relatively easy to manufacture and is torsionally stiff enough for a chassis in FSAE, CMT wish to investigate the feasibility of a carbon fibre monocoque chassis. The main goals of this paper are to benchmark the current space frame chassis design, and investigate feasibility of a carbon fibre monocoque, while reducing the chassis' weight, and increasing its torsional stiffness without increasing manufacture time. Preliminary modelling indicates that a transition to a half monocoque will yield a weight drop of 18kg, and a full monocoque will yield a drop of 23kg. The monocoque can also provide a torsional stiffness of approximately 4000-10000Nm/degree. This wide range of values is due to the vastly different chassis geometries, composite fabric weights, resin types, and layup methods. Physical testing of the 2013 chassis revealed that it has a torsional stiffness value of 813Nm/degree (which correlates with preliminary FEAs). For CMT it would seem that based upon the 2013 car's performance, torsional stiffness is not particularly important in this particular case study. Flat panel testing was conducted, however the panels were not as successful as the author had calculated they would be. All carbon fibre laminates passed the skin shear test, however only the aluminium honeycomb panels passed the three point bend test for the side impact structure.
ABSTRACT In order to defeat under body blast events and improve crew survivability, a monocoque aluminum cab structure has been designed as a drop on solution based on the current M1151A1 (HMMWV) chassis. The structure is comprised of all 5083-H131 Aluminum alloy armor plates with various thicknesses. The structure design consists of the following new features: (1) Robust joining design utilizing interlocking ballistic joints and mechanical interlocking features, (2) unique B-pillar gusset design connects roof & floor with B-pillar & tunnel, and (3) “Double V” underbody shaping design. The TARDEC designed, integrated & built vehicle achieved no crew core body injuries for a vehicle of this weight class and demonstrated meeting the crew survivability objective when subjected to a 2X blast during the live fire underbody blast tests. These efforts help to not only baseline light tactical vehicle capabilities, but also validate the possibility of meeting aggressive blast objectives for light tactical vehicles. These results provide government-owned designs that are scalable and actionable solutions for future HMMWV fleet upgrades.
ABSTRACT Since the development of combat vehicles for military use, such as tanks, infantry carriers, gun transports, etc. the main approach has been a monolithic structure that has been described as monocoque. This approach has been the standard–bearer since the inception of modern combat vehicles. Since the end of the Cold War, the world has become a much more “Multi–Polar” world. The U.S. is not locked in a static, monotonic engagement against the Soviet Union and its allies. The nature of the threat has changed. The U.S. Army is looking to make its Combat Vehicle fleet lighter and more adaptable to new technology and changing environments. By doing so the U.S. will be better able to project forces where they are needed. Lighter weight means more flexibility in transportation of equipment to various locations. In addition, the U.S. Army will be better able to deploy forces that have the latest and/or the most desirable protection required for the specific engagement they may encounter. The U.S. Army would like to investigate the uses of a space frame, if and where appropriate on their combat vehicle systems. This would be a definite paradigm shift in the development of combat vehicle systems. This article talks about the misconception that space frames are a “parasitic weight” to the system. The belief is that a monocoque approach is efficient because the material thickness is driven by survivability requirements and not structural requirements. It is said that once you meet the survivability requirement you will have enough structure. Therefore, adding a space frame structure is just adding weight. This article looks to dispel this belief. Over the last fifteen years, the Army has done several programs that have been able to shed more light on this issue. While it is true in some cases that a space frame would not be efficient, and therefore be adding weight. It is not always true. This article shows the studies and development programs that drive that conclusion. Space frames offer a potential to reduce weight and increase modular flexibility. By taking a look at studies and developments that, have been done over the last fifteen years we hope to begin the dispelling of the “parasitic” weight myth, and to be able to engage in a more in–depth look at exactly how to use monocoque and space frame structures in a judicious way to make our future vehicles better.
ABSTRACT This paper describes two phases of full scale testing performed on a Bell Helicopter Textron Canada Limited (BHTCL) composite monocoque tailboom manufactured using Automated Fiber Placement (AFP). This technical demonstrator tailboom was designed for use on a Bell 407 model as part of a collaboration program with Bombardier Inc., Composite Atlantic Ltd. and the National Research Council Canada (NRC). The tailboom cone consisted of a skin made from an AFP layup of carbon epoxy fiber tape combined to a hand layup made from fabric. The skin is then bonded to six hand layup frames. The fatigue test objectives were to validate the component to flaw tolerant safe life requirements and establish damage tolerance to light and medium caliber ballistic impacts. The test article, containing embedded flaws, impact damages, and representative repairs, was subjected to a full four lifetime fatigue test at NRC. All testing during this phase was conducted at 250 °F 'hot-dry' conditions to simulate operating temperatures seen in service. The test article successfully sustained four lifetimes of fatigue testing, followed by residual strength testing to both limit and ultimate loads. In the second phase of the full scale testing, the article was subjected to six ballistic impacts with deadweights replicating a critical load condition in the field, interspersed with short 'go-home' fatigue cycling in the laboratory. Regular inspections and near-real-time data analyses were performed throughout testing. No permanent deformation, new damage or existing damage growth was sustained by the tested composite components during the fatigue tests, subsequent residual strength tests, or fatigue loads following ballistic impact, thereby proving the flaw and damage tolerance capability of the structure.
While many composite monocoque and semi-monocoque chassis have been built there is very little open literature on how to design one. This paper considers a variety of issues related to composite monocoque design of an automotive chassis with particular emphasis on designing a Formula SAE or other race car monocoque chassis. The main deformation modes and loads considered are longitudinal torsion, local bending around mounting points, and vertical bending. The paper first considers the design of elements of an isotropic material monocoque that has satisfactory torsional, hardpoint, and vertical bending stiffness. The isotropic analysis is used to gain insight and acquire knowledge about the behavior of shells and monocoque structures when subjected to a vehicle's applied loads. The isotropic modeling is then used to set initial design targets for a full anisotropic composite analysis. The flexibility in composite layout and core design coupled with the superior material properties of carbon fiber composites is used to design and move toward an optimized monocoque composite design and layup to obtain satisfactory torsional, hardpoint and bending stiffnesses with minimal weight. Finally, some fatigue analysis considerations are outlined with emphasis on the endurance limit of the monocoque for a specific life span. The methods presented in this paper should be helpful in designing a monocoque structure chassis for FSAE race car or other applications.
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