Adhesion: Bonds and Adhesion: Bonds and ForcesForces

Jose TreviñoJose TreviñoDavid LeppoDavid Leppo

E3 Teacher Summer Research Program

Texas A&M University

MotivationMotivation• Why are adhesives important?Why are adhesives important?

– Important part of everyday items and Important part of everyday items and cutting edge technology.cutting edge technology.

– Allows for objects to be bonded without Allows for objects to be bonded without damaging them.damaging them.

• What are some common What are some common applications?applications?

ApplicationsApplications

Flexible Displays

Flexible Solar Panels

Automotive ElectronicsAluminum Siding

Everyday Electronics

Coated Containers

Oil Filters

Oil Filters

What properties are the What properties are the focus of project?focus of project?

TensionTension ShearShear

Homogeneous Heterogeneous

Adhesive

Shear / Tensile Test in the Shear / Tensile Test in the LabLab

• Applies Tensile Applies Tensile or Shear Stressor Shear Stress

• Depends on the Depends on the orientation of orientation of the materialthe material

Simple Adhesive Test for Simple Adhesive Test for the Classthe Class

• How do we test adhesive strengths?How do we test adhesive strengths?– Measure maximum shear force Measure maximum shear force – Measure maximum tensile forceMeasure maximum tensile force– Determine catastrophic failure pointDetermine catastrophic failure point

• Presents need for two simple test rigsPresents need for two simple test rigs• How do we capture attention of How do we capture attention of

students?students?

Crazy ScenariosCrazy Scenarios• Stilt HouseStilt House

– Build house on stiltsBuild house on stilts– Use adhesives to bond materialsUse adhesives to bond materials– Flood region: impact on adhesiveFlood region: impact on adhesive

• Mars BridgeMars Bridge– Use adhesive to build bridgesUse adhesive to build bridges– Low supplies on MarsLow supplies on Mars

Crazy ScenariosCrazy Scenarios• Adhesive to hold protective foam Adhesive to hold protective foam

on space shuttleon space shuttle– Need strong, non-corrosive adhesiveNeed strong, non-corrosive adhesive– Use least amount possibleUse least amount possible– How will you test its strength?How will you test its strength?

• Suspended Underwater PlatformSuspended Underwater Platform– BuoyancyBuoyancy– Waterproof adhesiveWaterproof adhesive– Water pressureWater pressure

Conceptual Shear Test RigConceptual Shear Test Rig• Measure the failure limit of shear Measure the failure limit of shear

forces on adhesion.forces on adhesion.• Measure the cross sectional area of Measure the cross sectional area of

adhesion.adhesion.Load

Adhesion

Shear Force Test RigShear Force Test Rig

Data Collection (Shear)Data Collection (Shear)• Comparing force at failure point and Comparing force at failure point and

cross sectional area.cross sectional area.

Contact SurfaceForce (lbs)

Stress (psi)Length

(in) Width (in) 2 * Area (in2)2.5 0.25 1.25 4.6 3.7

3.25 0.25 1.625 11 6.75.25 0.25 2.625 28 10.6

Max Shear Force vs AreaMax Shear Force vs Area

0

5

10

15

20

25

30

0 0.5 1 1.5 2 2.5 3Area (in sq)

Forc

e (p

si)

TAKS Objectives: TAKS Objectives: Mathematics 9-11

•Obj. 3: The student will demonstrate an understanding of linear functions.

•Obj. 8: The student will demonstrate an understanding of the concepts and uses of measurement and similarity.

•Obj. 10: The student will demonstrate an understanding of the mathematical processes and tools used in problem solving.

Conceptual Tensile Test RigConceptual Tensile Test Rig• Measure the failure limit of tensile Measure the failure limit of tensile

forces on adhesion.forces on adhesion.• Measure the cross sectional area of Measure the cross sectional area of

adhesion.adhesion.Load

Adhesion

Alternative Tensile Test - Alternative Tensile Test - MagnetsMagnets• Use magnets instead of adhesionUse magnets instead of adhesion

– Faster testingFaster testing– CleanerCleaner– Better ResultsBetter Results Load

Magnets

Test Rig for Tensile Test Test Rig for Tensile Test (Magnets)(Magnets)

Data Collection (Normal)Data Collection (Normal)• Comparing force at failure point and Comparing force at failure point and

cross sectional area.cross sectional area.Contact Surface

Force(lbs)

Stress(psi)Length

(in)Width (in)

2 * Area (in2)

0.75 0.75 1.125 1.125 10.75 0.75 2.25 2.2 0.980.75 0.75 3.375 3.45 1.02

Max Tensile Force vs. AreaMax Tensile Force vs. Area

0

1

2

3

4

0 1 2 3 4Area (in sq)

Forc

e (p

si)

Force vs Cross-Sectional Force vs Cross-Sectional AreaArea

• Large cross-sectional area means Large cross-sectional area means more bonds to break. more bonds to break.

• The larger the cross-section, the The larger the cross-section, the larger the force required to cause larger the force required to cause failure. failure.

ResultsResults• Bonds should have constant strength Bonds should have constant strength

regardless of cross-sectional area. regardless of cross-sectional area. • Imperfections and non-uniformities in Imperfections and non-uniformities in

a material can cause deviations in a material can cause deviations in the measured values of strengththe measured values of strength

• What kind of relationship exists What kind of relationship exists between max force and area?between max force and area?

• Why is it important to know linear Why is it important to know linear relationships exist?relationships exist?

Cost of MaterialsCost of MaterialsItem Price ea8’ 2”x6” wooden beam $4.00Aluminum Sheet Metal $4.99Clear Pine Plank (2) $1.67Elmer’s Glue $1.57½ inch threaded bolt (2) $1.37½ inch hex nut (4) $0.25½ inch flat washer (4) $0.25

QUESTIONSQUESTIONS