COM­POS­ITE SHELLS

Fast Ford - - Ff Tech -

For most forms of mo­tor­sport and for the more en­thu­si­as­tic track driver a bucket seat with a com­pos­ite shell will be the pre­ferred choice. Th­ese seats tend to be both the strong­est and light­est avail­able.

The shells can be made from var­i­ous dif­fer­ent com­pos­ite ma­te­ri­als rang­ing from the cheap­est fi­bre­glass (or glass re­in­forced plas­tic) through to full car­bon fi­bre, with a mix­ture of com­bi­na­tions in be­tween. GRP is the weak­est op­tion purely be­cause of the strength of the ma­te­rial used, and many of to­day’s en­try seats from re­spected man­u­fac­tur­ers fea­ture a com­pos­ite made from a blend of GRP weave and Kevlar strands.

This gives in­creased strength and al­lows seats made from th­ese types of ma­te­rial to meet the strin­gent FIA tests, whereas some seats made from just GRP can­not meet the re­quire­ments of th­ese tests and can­not be granted with FIA ap­proval.

Other ma­te­ri­als com­monly used in­clude Kevlar/car­bon fi­bre, and a full car­bon fi­bre. The GRP/Kevlar tend to be the cheap­est, but heav­i­est of th­ese three com­pos­ites. Kevlar/car­bon is lighter and stiffer, but more ex­pen­sive. And the full car­bon is the light­est and stiffest of the three, but also costs the most. All three types, though, meet the FIA re­quire­ments and are all de­signed to with­stand im­pacts above and be­yond the FIA test­ing.

In or­der to achieve this in­cred­i­ble strength par­tic­u­lar at­ten­tion needs to be taken when it comes to con­struct­ing the shell. The com­pos­ite shells are all made us­ing qual­ity com­po­nents and ma­te­ri­als, al­though the ex­act de­tails of the man­u­fac­tur­ing process are closely guarded se­crets.

You can see from the bare shells, though, that metic­u­lous at­ten­tion to de­tail has been taken to en­sure the shells are as strong as pos­si­ble, with­out in­creas­ing the weight un­nec­es­sar­ily. Strate­gic ar­eas are high­lighted af­ter ex­ten­sive test­ing and com­puter-based stress anal­y­sis, and are given ex­tra ma­te­rial to in­crease the strength as re­quired. Ar­eas such as the spinal rib­bon on the GRP/Kevlar seats of­ten fea­ture an ex­tra ply to en­sure the shell is as rigid as pos­si­ble. This is not needed on the Kevlar/car­bon, and car­bon fi­bre shells be­cause the in­creased strength of the ma­te­ri­als used means it is not nec­es­sary.

An­other area on all seats which has par­tic­u­lar im­por­tance is the fix­ing points. Spe­cial steel plates with a cap­tive nut are lam­i­nated into the shell dur­ing the man­u­fac­tur­ing process. Th­ese ar­eas re­ceive ex­tra ma­te­rial to give added strength, and the plates them­selves are drilled to en­sure they bond into the com­pos­ite with max­i­mum ef­fect which pre­vents the nut from spin­ning free and de­tach­ing from the ma­te­rial when fit­ting the mounts.

As with the tubu­lar seats, com­pos­ite shells are de­signed to flex a lit­tle un­der im­pact. It helps dis­si­pate the en­ergy in the same was as a tubu­lar seat de­form­ing does, but as the com­pos­ite is more flex­i­ble it will ac­tu­ally re­turn to its orig­i­nal shape. This is why it is cru­cial to re­place a seat af­ter a big im­pact, as it may look al­right but you won’t be able to see if the com­pos­ite ma­te­rial has been dam­aged in any way. And when it comes to driver safety you sim­ply don’t take risks.

An­other ben­e­fit of us­ing com­pos­ites is the abil­ity to fea­ture more com­plex shapes and de­signs, such as those in­cor­po­rat­ing wrap­around head re­straints and be­ing able to work in con­junc­tion with ad­di­tional safety de­vices such as the HANS de­vice.

The type of ma­te­rial used is what gives the seat its in­her­ent strength Three of the most com­mon com­pos­ites used in­clude GRP/Kevlar, car­bon/Kevlar, and full car­bon fi­bre

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