[DeTomaso] Composite parts

j g notstock at yahoo.com
Tue Mar 6 10:17:33 EST 2012


FYI: one item that a lot of people who have not ever actually engineered or built composite parts using any technique;  may realize is that usually a composite part built to be a replacement for an aluminum part will usually be at or above the weight of the aluminum part it will replace. Especially when mechanical structures are added to provide load spreading for hinges attachment points and other loaded pieces. So the question  why composites ? Well , if properly incarnated the composite part can be made to have higher 
ultimate strength in certain axis over a metal part , does not suffer from the same cyclic fatigue mechanisms and can be made to be repaired in spot locations easier than the metal parts. do not have expansion or mechanical stress issues over temperature , But this usually comes with some gotcha type issues. first metals tend to be isotropic unless some sort of forging (stamping) causes grain orientation to increase the strength along specific directions of the part . Different weaves and layups allow composites to be formed and oriented in many cases to provide improved load capacity by the directional nature of the weave and layup. Most prepreg post cured carbon composites have very limited shelf life prior to incorporation into a part , require high temperature molds , and then result in a part that has a pretty crappy  surface finish unless a secondary coating process is added to the part to fill the fabric on the surface. Typical prepreg epoxy
 heat/steam cured prepregs have only 2-4% epoxy binder , to achieve the highest strength to weight ratio. This; if any body has ever seen a part right out of an autoclave;  has a very ugly surfacappearance becausese of the very small amount of epoxy in the system,  but is strong. Anattachmentnt to the composite require metallic, wood, or specialized load spreading plates to be bonded in such a manner that the shear or compression loads are distributed through a sufficiently large surface area to not locally load the fibers in the fabric
Carbon fibers can take huge tensile loads but fracture in shear or compression so the binder (epoxy) acts like cement in a structure and the weave /fiber  is just like the steere barar in a bridgIt's's orientation determines the ultimate directional strength . What ends up is that a carbon fiber hood for example may achieve a 10% weight savings over an aluminum part at the same strength ratio. However may eat all this up in the finishing process to make it cosmeticaly attractive. What composites do allow are very complex part geometries with very good orientation of stress control with less deflection and increased stiffness over a metallic part in certain applications . 
I build formula style race cars and aircraft parts . In all cases an aluminum part can be designed and built that is at the same weight with adequite strength , but requires sometimes significantly more labor and time than a composite part. Composite parts in the case of a survival cell are designed to absorbe impact loads by crushing , deforming and actually fall apart in a controlled manner with honey comb and cored designs that would be quite difficult or impossible to build in metalic structures at the same weight. For non load bearing structures then of course composites can produce a part that is lighter than a metalic part but has the problems of not being able to be attached with typical hinges latches etc without significant strengthing sections added.
 
 
Jg 

--- On Mon, 3/5/12, bill gaino <gaino at earthlink.net> wrote:


From: bill gaino <gaino at earthlink.net>
Subject: Re: [DeTomaso] Carbon fiber or fiber look hood and engine deck?
To: "michael frazier" <red3644 at hotmail.com>, garth_rodericks at yahoo.com, "pantera list" <detomaso at realbig.com>, knottsj at galstar.com
Date: Monday, March 5, 2012, 2:04 PM


Looks like the japan guy here with the Dawg.  http://www.teampanteraracing.com/index.php?option=com_g2bridge&view=gallery&Itemid=57&g2_itemId=1890

-----Original Message-----
>From: michael frazier <red3644 at hotmail.com>
>Sent: Mar 5, 2012 2:33 PM
>To: garth_rodericks at yahoo.com, pantera list <detomaso at realbig.com>, knottsj at galstar.com
>Subject: Re: [DeTomaso] Carbon fiber or fiber look hood and engine deck?
>
>
>Is the guy in the "Japanese Pantera" video the same one in the photo with Dennis TPR link below?
> 
>The duct in his hood is a pretty good idea...not making massive cuts to the front panel.  That particular
>execution looks like it would fill the trunk with water on a rainy day.  I would take the top edge and just
>lower it and make a flat contact surface across the bottom of the ducts.  Whatever....
>
>Michael Frazier
>Gruppo Rompiculi Corsa 
>
> 
>
>> Date: Mon, 5 Mar 2012 08:37:37 -0800
>> From: garth_rodericks at yahoo.com
>> To: detomaso at realbig.com; knottsj at galstar.com
>> Subject: [DeTomaso] Carbon fiber or fiber look hood and engine deck?
>> 
>> The Ex3 Pantera hood scoop:
>> http://www.ex3.com/racing/bodymod.html
>> 
>> Mad Dog's front hood scoop, which I believe he referred to as a "Gurney Scoop" when he had it fabricated a couple years ago:
>> http://www.teampanteraracing.com/index.php?option=com_g2bridge&view=gallery&Itemid=57&g2_itemId=1827
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