Experiments-Structure-Property Relations of beetle's exoskeleton

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Abstract

This study examined natural composite structures within the remarkably strong exoskeleton of the southwestern ironclad beetle (Zopherus haldemani). The ironclad beetle’s cuticle was primarily comprised of chitin fibers and proteins that were organized into four layers: the epicuticle, exocuticle, endocuticle, and epidermis. Structural and nanomechanical analyses revealed that each layer performed a distinct function, with functionally gradient materials joining them together. The outer layer of the epicuticle consisted of waxy, polygonal walls (~2 µm in diameter) with waterproofing and anti-adhesive properties to inhibit microbial contamination. The exocuticle exhibited the greatest Young’s modulus (~15 GPa) and hardness (~800 MPa) values; providing high strength properties. While the endocuticle produced lower modulus (~8-10 GPa) and hardness (~400 MPa) values than the exocuticle, it is likely that this layer provided additional strength through fibrous stacking layers, known as Bouligand structures. Lastly, the most inner layer, the epidermis, exhibited elastic moduli of ~2-3 GPa and hardness values of ~ 290 MPa. As the softest region, the epidermis allowed for the attachment of muscle and soft tissue to the exoskeleton. These findings can be applied to develop innovative, fiber-reinforced composite materials.


Polishing prodecures for beetle exoskeleton

File:Beetle exoskeleton preparation.pdf

Set up a cup of 1/4 Dawn dishwashing soap and 3/4 water, then put in 8 cotton balls.

1. Attach Rondo Disc and 600 Silicon carbide paper

Set up polisher: 
(a) 150 RPM
(b) Time – 1 minute max on paper 
(c) Force — 15 N 
(d) Water — On 
After Grinding, if scratches aren't uniform, grind longer. 
Clean: 
(e) sample with water and use one of the cotton balls (it is ok to rub hard) 
(f) ring guard 
(g) mover plate 
(h) platen 
(i) through away used carbide paper 
(j) Rondo Disc - dry off and put away 

2. Attach Fuga Disc and 2400 Silicon carbide paper

Set up polisher: 
(a) 150 RPM 
(b) Time - 1 minute max on paper 
(c) Force — 10 N 
(d) Water — On After Grinding, if scratches aren't uniform, grind longer. 
Clean: 
(e) sample with water and use one of the cotton balls 
(f) mover plate 
(g) platen 
(h) through away used carbide paper 
(i) Fuga Disc - dry off and put away 

3. Attach Rondo Disc and 4000 Silicon carbide paper

Set up polisher: 
(a) 150 RPM 
(b) Time - 1 minute max on paper 
(c) Force — 10 N 
(d) Water — On 
After Grinding, if scratches aren't uniform, grind longer.
Clean: 
(e) sample with water and use one of the cotton balls 
(f) ring guard 
(g) mover plate 
(h) platen 
(i) through away used carbide paper 
(j) Rondo Disc - dry off and put away 

4. Attach DP-FLOC pad with Rondo Disc for 3µ

Set up polisher: 
(a) 150 RPM 
(b) Time — 3 minutes 
(c) Force — 10 N 
(d) Water — Off 
Put a 'Z' Pattern of Red Lubrication and 5 drops of 3 µ DP-Suspension on disc before starting. 
Start Polisher — Every 10 seconds add 4 to 5 drops of Red Lub. Every 20 seconds add 2-3 drops of 3 µ DP-Suspension to disc. Just to keep moist, not wet. After Polishing, if scratches aren't uniform, polish longer. 
Clean: 
(e) sample with water and use one of the cotton balls (do not rub hard) 
(f) ring guard 
(g) mover plate 
(h) platen 
(i) Do not remove pad from Disc — Rinse and dry with squeegee' dry with air and put away 

5. Attach DP-FLOC pad with Rondo Disc for 1 µ

Set up polisher: 
(a) 150 RPM 
(b) Time — 2 minutes 
(c) Force — l0 N 
(d) Water — Off 
Put a 'Z' Pattern of Red Lubrication and 5 drops of 1 µ DP-Suspension on disc before starting. 
Start Polisher — Every 10 seconds add 4 to 5 drops of Red Lub. Every 20 seconds add 2-3 drops of 1µ DP-Suspension to disc. Just to keep moist, not wet.
After Polishing, if scratches aren't uniform, polish longer. 
Clean: 
(e) sample with water and use one of the cotton balls (do not rub hard) 
(f) ring guard 
(g) mover plate 
(h) platen 
(i) Do not remove pad from Disc - Rinse and dry with squeegee, dry with air and put away 

6. Attach DP-FLOC pad with Rondo Disc for 0.25 µ

Set up polisher: 
(a) 150 RPM 
(b) Time — 2 minutes 
(c) Force — l0 N 
(d) Water — Off 
Put a 'Z' Pattern of Red Lubrication and 5 drops of 0.25 µ DP-Suspension on disc before starting. 
Start Polisher — Every 10 seconds add 4 to 5 drops of Red Lub. Every 20 seconds add 2-3 drops of 0.25 µ DP-Suspension to disc. Just to keep moist, not wet.
After Polishing, if scratches aren't uniform, polish longer. 
Clean: 
(e) sample with water and use one of the cotton balls (do not rub hard) 
(f) ring guard 
(g) mover plate 
(h) platen 
(i) Do not remove pad from Disc - Rinse and dry with squeegee, dry with air and put away 

7. Attach OP-S MD Chem Cloth

Set up polisher: 
(a) 150 RPM 
(b) Time — 1 minute 
(c) Force — 15N 
(d) Water — Off 
Set up a cup of OP-S, 2 OP-S to 1 water ratio. 
Pour a puddle of OP-S on MD Chem Cloth 
Start Polisher — keep the cloth wet not moist. Continuously drip the OP-S onto the cloth
After polishing sample, check for scratches, polish longer if there are any scratches. 
Clean: 
(e) Direct water onto MID Chem Cloth and squeegee to thoroughly clean cloth. Also, squeegee dry and put away. 
(f) sample with water and use one of the cotton balls (lightly wash, barely touching sample) 
(g) ring guard 
(h) mover plate
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