Hello, I have a challenge, which is beyond my abilities and have joined the forum hoping to get some informed opinion and figures concerning shear strength relating to riveted components.
I hope you don’t feel this is too cheeky.
OK here’s the story. I own an Aston Martin Vanquish S. The frontal nose cone is a composite around 5mm thick. Below this is located a splitter the full width of the nose cone, this is formed from a glass fibre material and is around 2mm thick max and is profiled to give it some added strength.
The splitter is held onto the underside of the nose cone using VHB tape running the full width of the splitter and 13 rivets along the back edge of the splitter which secures it to the underside of the nose cone.
Now when I bought the car, the splitter was missing. I understand that the car had had a frontal impact which had damaged the nose cone and presumably smashed the splitter. The original rivet holes were deformed due to this impact.
Aston Martin fitted a new splitter for me at great expense and after driving the car for roughly 20 miles I found that the splitter had disappeared. The car did not suffer any impact, but would have been under some load in terms of airflow and heat.
Aston Martin claim that I must have hit something, despite the fact that there was no damage to the car of any kind. I claim that the new rivets holding the splitter should not have been refitted to the original deformed holes. Aston Martin state that the splitter can come off if sustaining an impact of 1 MPH. This seems incredible.
So here’s why I’m requesting some engineering calculation.
Is it possible to calculate the force required and therefore the speed, based on the information provided above and a vehicle weight of 4,100lb to:
A. Shear the rivets and VHB tape in a horizontal direction, resulting in the splitter dropping off the car. This would indicate the speed required to achieve this outcome
B. Rip out the rivets and shear the VHB, assuming a 25% reduction in effective rivet holding strength due to deformed rivet holes. This would also indicate the speed required to achieve this outcome
If any helpful engineer is interested in calculating some numbers and wishes to communicate, my own email address would be best, I can then also email a picture of the nose cone and splitter which might help clarify the make up and location of the parts Email - [email protected]
Thank you and regards