.:: CHASSIS CONSTRUCTION METHOD ::.

.:: Manufacture of Composite parts ::.

A by Moulding :
1 Fibre (in cloth form) and Resin
2 Mould
B by Moulding with Vacuum :
1 Vacuum Pump
2 Pressure Bag
3 Fixing Screws
4 - Mould
5 Fibre(in cloth form) and Resin

The production of parts using Fibre and Resin is feasible with low investment costs and offers a high flexibility at design level since it is easy to modify the component shape.
The most simple manufacturing method (Fig. A) is to place the fibres, which have been woven into a cloth with orientation as required, into the mould (which has the shape of the final desired component) and then to apply the resin with a brush or a roller. The resin will set without pressure application, at ambient temperature, or the mould can be heated in an oven.
More modern methods use pre-impregnated cloth and the use of an "auto-clave" or pressure and temperature regulated oven, which additionally compacts the material to give a denser, stronger final component.
Alternatively, Fig. B illustrates the use of a pressure bag, which compacts the fibre material whilst a vacuum is applied, to squeeze out excess resin.
The above techniques can be used to create simple panels, of a single material, or also "sandwich composite panels". This second type of construction consists of a core of stable material with specific characteristics (such as extremely high compressibility, ie/ Nomex Honeycomb Paper ) which is bonded between two outer skins of Carbon-Fibre.
Thanks to this construction technique, the thickness of the panel is increased with only a small weight increase, but with a notable increase of energy absorption capability.
Normally, a core of 5-10mm is used for the non-structural panels, whilst 10-20mm core is used for load-carrying components.
In the manufacturing of sandwich panels, the anisotropic or orthotropic nature of the fibres and core material must be understood and considered, according to the applied load vector on the panel.
The Anisotropic Material property is the characteristic of the material to exhibit different strength in each direction, such as carbon-fibre which has extremely high tensile strength, but low bending strength. Metals, on the other hand, have similar properties in all directions.
These special properties require careful analysis and experimentation to exploit their advantages, and a working prototype, especially a competition vehicle, is the ideal test bench for constructing parts, identifying problems and creating methodologies to resolve them.


.:: CHARACTERISTICS AND COSTS ::.

The comparison between composite materials and traditional manufacturing materials such as Steel and Aluminum can be made only by bearing in mind several factors.
The foremost is naturally the density which for steel is on average 7.8 gr/cm3, whilst for composites it is between 1.2 up to just over 2 gr/cm3, depending on the core material used, the proportion of core/fibre, and the amount of resin used to bond together the fibres.
It is important to note that, for corresponding cross-sections of material, a composite material has considerably increased strength, for example a simple glass fibre with parallel fibres set in polyester resin has a tensile strength of between 40 a 150 kg/mm2 depending on the fibre-density, compared to semi-forged aluminum with a tensile strength 30 kg/mm2.
The same differences can be found for other deflection modes.

.:: PROPERTY TABLE FOR VARIOUS COMPOSITES ::.

Property Unit Glass Fibre
E-type
Glass Fibre
R-type
Kevlar
49
Carbon
A mod.
Carbon
A res
Boron
Density gr/cm3 2.60 2.55 1.45 1.95 1.75 2.6
Load at yeld
in tension
kg/mm2 340 440 350 220 250 320
Longitudinal
elastic modulus
kg/mm2 7300 8600 13500 38000 26000 40000
Elongation
at yeld
% 4.5 5.2 2.5 0.6 1.0 0.8
Proportion of composite
wrt to filler resin
% 60 60 60 60 60 50
Composite density gr/cm3 2.04 2.01 1.37 1.65 1.55 1.90

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