Lotus TURBO ESPRIT Service Manual page 78

SECTION BB
Page
The outer surface of a composite panel is sealed by a thin
layer of 'gel coat'. If the panel is deflected beyond its
limits of flexibility the gel coat will be overstressed and
cracks will result, although the panel will return to its
original shape.
A
steel panel similary treated would become permanently dented.
The cracking may be confined to the surface gel coat, with no
reduction in panel strength, but if damage is more severe the
composite structure below the gel coat may be weakened.
Localised repairs can be made in either case. Gel cracks may
not appear immediately after overstressing because the effect
can be masked by the flexibility of the paint finish which
covers the gel coat. In some instances gel cracks can take
as long as three months to appear.
Gel cracks can be caused by, for example:-
Sitting or leaning heavily on the bonnet or any other
flexible panel.
Knocking doors against obstructions when opening.
Dropping a sharp or heavy object on a panel.
Allowing unsecured items to slide about in the boot (trunk).
Closing bonnet (hood) or boot (trunk) onto projecting objects,
e.g. luggage or tools.
Attempting to deflect or remove, by force, parts attached to
composite panels e.g. mirrors, locks, aerial etc., (action by
vandals or even some mechanical car washes).
Incorrect jacking.
Collision with heavy rigid object.
Note that bumpers are sacrificial members which will absorb
shock loads, thus protecting body panels. Exceeding bumper
load factor may cause gel crazing of body panels.