# Effects of size and speed on model airplane crashes

I am looking for an equation that correlates material failure and collision speed;
so that I can better understand the effects of size and speed on model airplane crashes.

Is there an equation that correlates an object's length and speed to material failure,
for one-dimensional elastic collision of into a rigid barrier,
given elastic modulus and specific strength?

This is a guess:
specific strength :: speed^2 * length​
but it's probably more complicated than that.

Thank you.

CWatters
Homework Helper
Gold Member
I'm aware of a general rule that says light models bounce but have never seen anyone do a rigorous analysis.

How about looking at the energy..

KE = 0.5mV2

That has to be absorbed by the structure flexing on impact.

Looks like two factors matter.. The mass and the flexibility.

Some modern indoor RC planes are very light and very flexible, their structure can be distorted considerably without breaking so the available "stopping distance" is quite large and the resulting deceleration and impact forces quite low. I'm thinking of planes similar to this that are made of thin carbon fibre rod.

http://www.hobbyexpress.com/images_products/528613_large.jpg

caz
Gold Member
For plastic flow in 1D, look up the paper by wilkins and guinan on the taylor impact test. My instinct is that you might need to look at bucking theory. Try the book structural impact by jones.