Plastic engineering question

When you say 'plastic' can we assume that you mean some thermoplastic whose elements will be injection molded, extruded or thermoformed as opposed to cast from resin components and other filler elements to change final rigidness?

Analysis is likely to be valuable due to the inherent differences between wood and (which?) Plastic(s) to the nature of how this article will be used ____ how many times in what way before or if you could expect catastrophic failure which will be _what?__ Is the item going to be warranted? Is any instruction outlining maximum application useages going to be visible in what language? You don't mention any special conditions - is this furniture for Children, elderly, physically challenged or is it warranted to perform in any minimum way?

Like it or not, you probably will own the outcome - and because the strain may have other impacts on the final use, bending of plastic versus the ridigity of wood might be an issue in usability - for instance if you sit in the middle of plastic chaise or chair for a long enough period and eventually your backside is on the floor - the product may last, but the product won't be functional. And you might want to 'load' the furniture article with the same load in various ways - concentrated versus spread, the speed with which is is done, at various temperatures etc.

Here is in an excerpt from a report done on Plastic versus Wooden traffic posts - which is a pretty simple shape with a known needed outcome -

"4.0 ARC RESULTS:

PHYSICAL PROPERTY MEASUREMENTS OF PLASTIC VERSUS

WOOD GUARDRAIL POSTS

The wood posts show that they require a greater load giving them a greater

maximum stress at failure but they also bend considerable less before they fail.

The plastic posts do not require as much load to cause failure but they bend

considerable more before break, which means they require a greater strain at

break.

The Amity plastic post formulation of 50/50 oil jugs to chemical jugs showed that

at ambient temperatures and at – 30ºC the posts absorbed at least as much

energy as the wood posts."

excerpted from:

Title

RECYCLED PLASTIC GUARDRAIL POSTS FOR USE IN A

FLEXIBLE, LONGITUDINAL ROADSIDE (WEAK POST) BARRIER

Type of Report

Interim

Author(s)

Ted Harrison, P.Eng.

Googled at +strain +" wood versus plastic"

second item down -

Hope helps

Jim