I have a uniform load applied to the underside of a plastic sheet which is to be resisted by the combination of a bolt, washer, and nut as depicted below (the other end of the bolt is secured and will not budge).
The thickness of the Luran S 777k ASA (Acrylonitrile Styrene Acrylate) plastic is currently unknown, but to get the ball rolling let's just say it is 1/8" thick (EDIT: confirmed). The plastic will bear directly on the square washer.
For modeling purposes, I have decided to assume the plastic is totally fixed/rigid and that the load is being applied to the bolt. In this model, it is the washer that is bearing on the fixed plastic.
I expect that the limiting factor of this system is going to be the pull-through capacity of the plastic as (I assume) the washer will tear it apart way before the washer or the bolt fail. How can I determine the pull-through capacity of this system? Is my assumption that the pull-through capacity of the plastic is the limiting factor valid?
My idea is to simply obtain the shear resistance of the plastic material online somewhere, and calculate the pull-through capacity like so:
- Shear strength of the material is $\tau_{\text{ASA}}=??$
- Load-resisting cross-sectional area: $$A=4s_{\text{washer}}\cdot t_{\text{plastic}}$$
- Therefore the pull-through capacity of washer bearing on plastic is: $$P_t=\tau_{\text{ASA}}\cdot 4s_{\text{washer}}\cdot t_{\text{plastic}}$$
However, I'm concerned there may be other considerations at work here that I need to take into account. Is it really this simple?
Thanks to hazzy for the simple but reassuring answer, and the points he made.
It turns out that the limiting consideration for this particular problem seems to be fatigue/cyclic bending of the plastic around the washer, since in actuality the load is being applied at either end of the plastic section (instead of uniformly as I proposed in the model above).
Luran S 777k ASA
a brittle or ductile material? Are there supports close to the washer or are they far away? $\endgroup$