Stress, Strain & Composite Material

We have incorporated nanotubes into polymer composites to determine structural failures before they become critical by assessing stress and resistance over time in 4-point bending. We then compare the change in resistivity in coordination with applied stress and strain and evaluated their usefulness as a predictor of failure in composite materials.

Michael Day1, Sarah Woodward2, Jandro Abot3

1Reading High School, Cincinnati, OH; 2Woodward High School, Cincinnati, OH; 3Department of Aerospace Eng. & Eng. Mechanics

ReferencesRefer to individual Lesson Plans

AcknowledgementsWe would like to thank The University of Cincinnati and the National Science foundation For this opportunity as well as the support staff: A. Kukreti, PhDA. Burrows, PhDJ. Abot, PhDYi Song, PhD CandidateSandeep Medikonda, PhD Student

Solve for variables given a formula Students will take data and infer if it will be linear or another function. Students will be able to graph the data and make a scatter plot. Then find the function.

Objectives:

Engage: How to bend materials!

Explore: Is the data linear? What else effects the bending?

Explain: More than one variable can affect the outcome.

Elaborate: Find the function. We will use calculators and excel spreadsheets to find a best fit model.

Evaluate: Students will plot data, find functions, predict linearity, and find slope.

Teacher Guide, Day 1:

Teacher Guide, Day 2:

Engage: RET project and all the cool data I collected.

Explore: Equations I used and manipulated.

Explain: Re-teach how to solve for certain variables given equations. 

Elaborate: Students make their own self-sensing composite material.

Evaluate: Lab reports will be started, along with solving scientific equations for a specific variable.

Michael Day, Pre-Calculus Lesson:

Teacher Guide, Day 3:

Engage: Destroy a bridge!

Explore: Why did it fail? Could a sensor have helped detect when it was going to happen?

Explain: Show samples from RET project with CNT threads.

Elaborate: Students do their own experiment.

Evaluate: Finish lab report and make a poster with findings. Present, as a group, the findings to the class.

Sample: Yes, we broke it!!!

CNT Diameter

Materials Lab Equipment

A: Students develop skills for solving equations, gather and analyze information, C: Students identify the skills needed for a career in research. Understanding that sometimes answers are not known.S: Students are able to communicate findings to others. They shall be able to see other uses for the technology involved.

ACS Connections:

Materials

Abstract

Using weight to bend the pipe!

How much was the dis-placement?

Using weight to bend the wood.

Increase the weight and what happens to the displacement?

12

* 3hwI y

I

M* yEI

M*

*

Inertia (I) as a function of width (w) and height (h)12

* 3hwI

Examples of equations that were used in the RET project:

Stress (σ) as a function of Moment (M), Inertia (I), and half the height (y)

yI

M*

Strain (ε) as a function of Moment (M), Inertia (I), Elasticity (E), and half the height (y)

yEI

M*

*

Objectives:

Day 1-2:

Day 3:

Day 4:

ACS Connections:

Materials

Goals: Students will understand the function of the skeletal system, stresses incurred by different bones in the human body and be able to describe the differences in normal and diseased bone and how it reacts to its environment. 

Objectives: 1. Students will be able to identify the 4 different types of bones (long, short, flat and irregular) and describe common stresses normally sustained.2. Students will be able to compare the functionality of normal and diseased bone

PPT for Skeletal system Worksheet for PPT (guided notes) balance scale Marieb text Samples of bone, shank, pelvis, vertebrae method for measuring volume Lab notebooks Lab directions light microscopes/bone slides

Teacher

Day 1-2 Warm-up ? What holds us up? Describe how our support system works. (5 min) Open section with Bulldog Feud, to assess prior knowledge. Intro to the human skeleton PPT with coordinating worksheet

Student:

Complete warm-up  

Compete for a prize with teams Fill in worksheet while going over chapter data

Teacher

Warm-up?; What chemicals are an important part of bone, (5 min)Begin Lab  Assign research question:

Research Osteoporosis: describe the process that occurs in the development of osteoporosis. Compare the structure of normal bone to the structure of osteoporotic bone. Describe how normal bone functions.Predict how osteoporotic changes will affect the function of bone under stress.

Student:

Record initial data (mass, volume calc density} on bone,

Put bone in vinegar

Use microscope to view slides of bone, draw diagram of what is seen at 4x and 10x

Teacher

Warm-up?: What are stress and strain?

Introduce the concept of stress and strain and demonstrate how it is tested

Student:

Remove samples from vinegar and rinse with water.

place in hood to dry

Design of a method to test how much stress, sketch design in lab notebook, begin to build.

Day 5-6:Student

Record dry data, draw a diagram of test, test stress/strain

Enter data into Excel and graph results

Complete conclusion

Teacher

Warm-up?; What do you think will happen to the decalcified bone under stress, how will that compare to normal bone.

Remind students of research presentations

Day 7:AssessmentStudents will present co teach exercise and be graded on rubric for comprehension.

Students will be given a series of free body diagrams of different types of bones and be asked to label the forces that act on the bone.

Predict the location of fractures when different types of bones are put under stress, describe the difference in the location of fractures and the force necessary in diseased bone.

Sarah Woodward, Anatomy Lesson:

A: Students must understand how unhealthy behaviors can affect them, poor nutrition can eventually lead to osteoporosis. Understanding is the beginning for long term prevention.

C/S: Many students are interested in careers in medicine or research. The ability to take a common problem and define a need and then solve that need is the basis of engineering solutions to the benefit of society. 

Observe the difference in the resistance with increased weight!WHY?