Case Study on Helmet

1. CASE STUDY
The following case study is on
HELMET
From every product Customer has some expectations.
Here are the customer requirements:-
1. Light weight
2. Impact resistance
3. Good visibility
4. Low noise
5. Easy to put on/remove
6. Comfortable
There are some objectives too:-
1. Determine relative importance of requirements

2. 2. Establish detailed requirement/parameter relationships
3. Identify idealised target local target satisfaction
thresholds
4. Optimise actual parameters to maximise design
merit
5. Unit Cost analysis
SELECTION OF MATERIALS:-
The selection chart helps identify materials that have high toughness and sufficient
strength. Composites, most metals, and many polymers look good. Another
requirement for hard hats is that they should be inexpensive and low weight.
Polymers best meet all these needs and are also easy to manufacture. In fact hard
hats are mainly made from polycarbonate or ABS and fitted via adjustable
polyethylene straps inside the shell.
A Cycle helmet must protect against the large impact on the head received during a
crash. In this case it doesn't matter if the helmet is permanently damaged (all
manufacturers recommend replacement after an accident), but it must absorb lots of
energy. The best materials for this are foams - they absorb lots of energy when they
are crushed. The main impact absorbing material in a cycling helmet is, therefore, a
moulded block of polystyrene foam, usually with a polycarbonate covering. These
materials are easily shaped - cycling helmets often have striking shapes to improve
their aerodynamic performance.
In 2013 a company called 6D is introducing a new approach to helmet liners. Their
motorcycle helmet has a hard shell, and uses EPS for the outer and inner layers of
the liner. Sandwiched between is a layer of plastic/rubber constructs in an air gap.
6D maintains that their design performs better in lower level impacts, and that the
airgap layer dissipates angular acceleration as well.

3. MANUFACTURING:-
There are three distinct parts to most helmets:- Shell, Liner and Strap.
Liners
The liner is the most important part of the helmet, the foam layer where the
energy of the crash is managed.
Bicycle helmet liners are mostly molded in Expanded Polystyrene (EPS) foam.
EPS can be made in layers with different densities to tune impact management,
permitting softer layers to crush in lesser impacts and harder layers to handle the
really bad hits. In some cases the density is varied around vents or certain areas of
the helmet to permit the helmet to meet impact standards while thinning the liner.
Shells
The shell for inexpensive helmets is just stamped PET (the material used for
bottled water containers) or a similar plastic. It is usually glued onto the liner, then
taped around the edge for appearance, although some use no glue and others have
no tape.
For more expensive helmets the shell is included in the mold when the liner is
expanded from the bead, and must therefore be polycarbonate or another higher
quality plastic that can take the heat of the mold (PET would melt).
Skate-style helmets and a few bicycle-style helmets have hard shells made of ABS
or polycarbonate plastic. BMX helmets (and a few older bicycle helmets) can have
composite hard shells, with layers of fiberglass or even kevlar fiber laid up in an
epoxy. ABS is molded, but Fiberglass shells are generally laid up by hand.

4. Straps
Helmet straps are generally made of nylon or polypropylene. They all look similar,
but vary considerably in fabric, surface finish, weave and other subtle
characteristics. For helmets with glued-on shells they are added to the liner before
the shell is glued on, and usually run across the top of the liner, covered by the
shell, or occasionally over the top of the shell. This is not possible when a helmet
is molded in the shell, since the heat of the molding process would damage the
webbing.

5. CONCLUSION AND FUTURE PROSPECTS:-
According to a survey, In the last decade accidents have decreased
considerably due to use of helmets. In conclusion, we could say that
helmets have a big future due to their increasing popularity of use; thus
material selection and design will lead that future in terms of
technology.
There will be much improvement in structure and technology of helmets,
thus, providing cheaper and reliable and quality production.