Purpose: Many shipped products and materials arrive damaged as a result of compressive forces. These products get squashed when they are stacked or when other objects crash into them. Working in groups, students will apply information about the diabolical ironclad beetle and physics principles to design, build and test protective packaging that resists damage from compression.
Procedural overview: After reading the online Science News article “The diabolical ironclad beetle can survive getting run over by a car. Here’s how,” students will analyze and discuss the physical characteristics that help the diabolical ironclad beetle resist crushing. A version of the article appears in the November 21, 2020 issue of Science News. Using this information and principles from physics, students will work in groups to design packaging that could protect the contents of a container from damage caused by compressive weight. Then, each group will build a prototype (preliminary model) of its design, test the prototype’s strength and durability and discuss the test results as a class.
Approximate class time: 2–3 class periods, or one class period per week over consecutive weeks
Want to make it a virtual lesson? This engineering task can be conducted virtually by holding group discussions using interactive meeting applications and by using video-sharing technologies to record and share their decision-making process. Students should be able to construct prototypes individually at home, and some testing for how well prototypes withstand compression may be done at home using bathroom scales and objects with measurable weights. Prototype testing is best done in the classroom where equipment such as force meters, balances and scales are available. Testing also can be done by the teacher and shared with students in videos from which students can gather and record data.
Materials for constructing a prototype (in classroom or at home), such as paper or cardboard of varying weights (ranging from newspaper to corrugated cardboard), egg cartons, tape, glues (flexible glues include white craft glue, contact cement, wood glue and hot glue; rigid glues include cyanoacrylates and 2-part epoxies), staples and a stapler, scissors or a craft knife
Materials for testing prototypes in the classroom, such as weights or household or classroom objects with masses from 1 to 4 kilograms (in sufficient quantity to combine to a total weight of about 25 kg), force meters, spring balances or scales
Computer with internet access
Interactive meeting and screen-sharing application for virtual learning (optional)
Interactive word processing, drawing or modeling for simultaneous participation (optional)
Audio or video capture hardware and editing software (optional)
Directions for teachers:
A force is a push or a pull on an object. Objects are subjected to forces when they interact with other objects. Newton’s second law defines a force (F) as the product of an object’s mass (m) and its acceleration (a), which is commonly expressed as F = m x a. Force is measured in Newtons (N); mass is measured in kilograms; the acceleration due to gravity is 9.8 meters/second/second. An object’s weight is the force on it produced by gravity.
Newton’s third law states that when one object exerts a force on a second object, the second object exerts a force that is equal in strength and opposite in direction on the first object. For an object at rest, the surface below it exerts an upward force equal and opposite to its weight.
A force diagram uses arrows to show the strength and direction of all the forces acting on an object. The direction of a force is indicated by the direction in which the arrow points. The relative strength or magnitude of the force is indicated by the size or length of the arrow. These diagrams help scientists and engineers visualize the forces acting on an object and identify where forces may be unbalanced. Portions of the system where forces are unbalanced commonly present opportunities to explore how structures absorb or disperse forces. An example of a force diagram showing boxes at rest on a surface can be found here. Note that in the example, Fg is the weight of the box (the box’s mass times the acceleration due to gravity), FN is the equal and opposite force that the ground exerts upward on the box and Fa is the force applied to move the box.
In this activity, students will evaluate the forces on objects stacked atop one another. In such situations, most scientists would construct independent force diagrams for each object, similar to the example found here. Students should do the same.
Although engineering practices have much in common with scientific practices, engineering has a different purpose and product than scientific research. The purpose of engineering is to apply scientific knowledge and an understanding of human needs to develop equipment or processes to solve problems that people encounter. Engineering is an iterative process, which means that it involves repeated cycles of development, testing and analysis to optimize solutions.
The engineering design process can be broken down into a few stages, with a variety of potential steps within each stage. Engineers must first define the problem to be solved, which they do by asking questions, conducting research and identifying criteria and constraints that allow them to identify potential solutions. Criteria commonly refer to specifications that the object or process must include to perform the needed function. Constraints are limitations to the implementation of the solution.
Once the design problem has been clearly stated and the criteria and constraints are identified, engineers develop solutions. This stage involves brainstorming and then evaluating potential objects, technologies or processes. In the third stage, engineers choose the most promising ideas and develop prototypes. They test the prototypes and analyze the results. Then, engineers optimize the solution by using the results to refine or improve the solution. When problems occur, engineers sometimes have to start over. The entire process may be repeated multiple times before achieving a solution.
Assign students to read the online Science News article “The diabolical ironclad beetle can survive getting run over by a car. Here’s how,” and answer the following questions as homework before the first class.
1. Describe two features of the beetle’s anatomy that make the beetle difficult to crush.
Tightly interlocked and impact-absorbing structures that connect pieces of the beetle’s exoskeleton help it survive enormous crushing forces. The first key feature is a series of connections between the top and bottom halves of the exoskeleton that use zipperlike ridges that latch the upper and lower parts together. The second key feature is a rigid joint or suture that runs the length of the beetle’s back and connects the left and right sides of the exoskeleton. The edges of this suture fit together like puzzle pieces and contain layers of tissue glued together by proteins.
2. How do the structures you identified prevent the beetle’s exoskeleton from being crushed?
The zipperlike connections around vital organs are stiff and resist bending under pressure. Connections near the back of the beetle are more flexible, which allows the exoskeleton to absorb compression. A suture connecting the left and right sides of the exoskeleton contains many layers of tissue glued together with proteins. When the beetle is squashed, tiny cracks form in the protein glue. These cracks absorb and disperse energy, which prevents the exoskeleton from snapping.
Before beginning the class discussion about “The diabolical ironclad beetle can survive getting run over by a car. Here’s how,” make sure students understand core concepts of physics related to forces and Newton’s laws of motion. With your class, review information about forces and Newton’s laws of motion found in the background section.
Review force diagrams with the class, and then have students attempt to answer the first question below individually or in small groups. After reviewing the answer to the first question, discuss and answer the second and third questions as a class.
Note that if students struggle to construct a force diagram showing all of the forces in the scenario encourage them to construct multiple diagrams that break the scenario into action-reaction pairs. Students should draw the forces of the beetle on the ground and the ground on the beetle. Then, students should draw the forces of the foot on the beetle and the beetle on the foot. Students can then combine those diagrams to show the directions and relative sizes of the forces between the beetle, the foot and the ground.
1. Draw a force diagram that shows the size and direction of forces exerted on a diabolical ironclad beetle’s body when the beetle is stepped on by a 60 kg (588 N) animal. Assume that the beetle’s mass is about 2 grams, so it exerts a force on the ground of 0.2 N.
Students’ diagrams should show a cross section of the diabolical ironclad beetle’s body based on the description of the beetle’s exoskeletal structure in the Science News article and on the photos and illustrations of the beetle’s body structure from the article and from other sources provided in the resources section. The diagram should show the force of the beetle (the beetle’s weight, or mass times the force of gravity) pushing down on Earth’s surface and an equal normal force of the ground pushing back up toward the beetle. Also show the force of the foot pushing the top of the beetle’s exoskeleton toward the ground and the normal force of the beetle’s exoskeleton pushing back against the foot.
2. Explain how features of the diabolical ironclad beetle’s exoskeleton change the direction and/or magnitude of the forces exerted on its body when it is stepped on.
The zipperlike connections between the exoskeleton’s top and bottom resist bending under pressure, and the flexibility in these connections allows the exoskeleton to shift the direction of force forward or backward along the beetle’s body, which decreases the impact of the force pushing downward on the beetle. The puzzle-shaped suture that runs down the center of the beetle’s back allows the exoskeleton to flex, which changes the angle or direction of the force pressing down on the beetle. The tiny cracks that form in the protein glue absorb and disperse energy, which decreases the impact of the force pressing down on the beetle’s back.
3. Modify your force diagram to incorporate information from your answer to the previous question. You may need to add, remove or modify the size or direction of arrows in your diagram.
In addition to changing the direction and length of the arrows in the original diagram, students may opt to add additional views of the beetle’s exoskeleton, including a side-view cross section or a top or bottom view to show the dispersal of energy laterally from the center of the beetle’s back toward the sides or anteriorly-posteriorly toward the front or back of the beetle’s body. Students may also wish to add microscopic zooming views to show how cracks form in the protein glue of the beetle’s exoskeleton and how the energy is absorbed or dispersed by that process.
Defining the problem
Begin by having the class discuss the design scenario and ask clarifying questions about the engineering design process and the various steps necessary to create a better container. Then, in groups, have students design and test a container prototype. The class will evaluate the various prototypes and discuss how the best ones might be optimized. To perform this discussion virtually, ensure that students have access to an interactive meeting application. Establish protocols so that students can indicate when they wish to contribute to the discussion and determine how they will signal agreement or disagreement with the class’s decisions.
Students may want to do additional background research on package design.
Encourage students to think about how packages or containers get damaged in transit. Ask students to list sources of forces that could lead to damage of shipping containers or boxes. Students should be able to describe how dropping, tossing and kicking packages can cause damage.
To focus students on the resistance of packages to compressive weight, you may need to explain that a significant amount of damage is caused when packages are improperly stacked, and the weight of overlying boxes causes the boxes near the bottom of the stack to fail. In many cases, entire pallets of boxes are stacked on top of each other, so the amount of weight borne by boxes at the bottom of the pile can be very high. Forces on cargo also change when ships, trucks or planes swerve, sway or hit bumps.
Guide students in a discussion about how businesses protect the contents of packages to reduce damage to the product despite damage to the packaging. Ask students why most products come in an otherwise empty box. Why are items usually padded with paper, plastic foam or air-pack materials? How do these padding materials contribute to the weight, cost and environmental impact of the product? How do these materials help the package resist crushing?
Based on the scenario and the discussion of shipping processes, have students answer the following questions as a class.
1. What engineering problem will your container design address?
My engineering tasks are to design and build packaging that will protect the contents of a container from damage caused by compressive weight during shipment.
2. What criteria, or requirements, would your solution need to meet in order to be successful? How would you know if your solution met these requirements?
In order to be successful, we must design a container that can enclose and protect its contents to prevent damage. It would need to be scalable in size so that it could be used to ship individual items and also be stackable for bulk shipments. A successful prototype would be a box or container that can withstand enough weight that its structure does not fail when weight is stacked on top of it.
3. What constraints would limit the success of your solution? Think about how the solution’s cost, its ease of use and other restrictions will affect how it could be used.
The cost of the materials or the manufacturing of the designed container would affect how widely the design could be used. The weight of the final container would need to be comparable to boxes and containers currently used, or the new containers may be too heavy to make replacing existing boxes worthwhile. If the process for using the new containers is too complex or requires special equipment, it may be difficult for manufacturers or shippers to adapt to the new containers. An ideal solution would be a reusable and recyclable product that is made from nontoxic materials and that reduces the amount of packaging waste.
4. How could you test prototypes to see if the criteria and constraints of the problem have been met? How could you measure results to compare design options?
I would need to create prototypes of each design option and test how each performs in a set of real-world applications. For example, I would need to test how much weight each container could hold without failing. To do that, I would need to test both the amount of weight the box can contain as well as the amount of weight it could support when empty and when full. For these tests, I would need to have weights or items of known masses, and I could measure the force on the box by using scales, force meters or spring balances. I would also need to perform tests in which I drop or strike the box to see if the container itself is damaged or whether any items inside are jostled or damaged. For these tests, I would need weights or items of known masses, and I would need to drop them from the same height or strike them with the same force for each test.
Designing a solution
Once students have clearly described a design problem and listed the criteria and constraints for a successful solution, have them work in groups to develop potential solutions. When performing this activity in a virtual or remote-learning setting, student groups will need to interact in breakout sessions using interactive meeting applications or via audio or video calls. The brainstorming step could be performed independently. Students would then bring ideas to the group for discussion and selection.
You might encourage students to research the most common shapes of shipping or packaging boxes, the sizes and weights of standard pallets or common methods of stacking pallets or containers for transit. This information may help students focus on specific points in the process where a solution could be targeted.
Students working remotely should use a shared drawing or modeling program, such as Google Draw, Sketchpad or AWW Board, in which all students can make and see changes to the sketches or models as the group collaborates in developing the design.
Have students answer the following questions with their group to guide the design process.
1. Brainstorm solutions for the engineering design problem you described. Use information about the diabolical ironclad beetle’s exoskeleton to guide your design. Sketch drawings using force diagram arrows to design possible solutions.
Answers will vary. Students should list a few different ideas for the shape of the container and for ways to incorporate zipperlike connections similar to the ones between the top and bottom of the beetle’s exoskeleton or connections similar to the ones that fit together like jigsaw puzzle pieces running down the beetle’s back. They also might discuss how to construct the box wall to approximate the beetle’s tissue layers connected by protein glue. Force diagrams should include proportional arrows that represent the force exerted by the weight of the box on the ground, the normal force in the opposite direction and any changes in the direction or magnitude of forces that are expected to occur as a result of the engineered structures.
2. As a group, choose the solution you think best solves the problem while meeting all the criteria and constraints. Describe that solution.
Answers will vary. Students may choose a solution that attempts to incorporate all of the features of the beetle’s exoskeleton, but many groups will choose to focus on only one or two of those features in their design. Sample answer: We are going to build a container from several layers of thin cardboard held together by white craft glue. The container’s top half and a bottom half will meet along an edge that fits together with interlocking ridges. The halves of the box will not be made of a continuous piece of cardboard with folds or seams at the corners. Instead, the vertical and horizontal sides of the box will be constructed of separate pieces of layered cardboard glued together at sutures that are shaped to fit together like interlocking puzzle pieces.
3. Create a sketch or a physical or computer model of the chosen solution. Include a force diagram that demonstrates how you think your solution will change the forces on the container.
Sketches and models will vary but should reasonably depict the proposed design. The force diagram should accurately depict the direction and magnitude of forces on the proposed container and how the container is designed to disperse energy to prevent damage when boxes are stacked on top of it.
Review group designs and provide feedback to help students optimize or adjust their designs or their force diagrams. Student designs should be clear enough that other students will understand the key features when the designs are presented. Student groups should present their designs to the class and explain how the group’s design will reduce damage to containers during shipment or storage. Students should make clear how they incorporated features of the diabolical ironclad beetle in their design and why those features were chosen. Students should answer questions from their classmates about their design and should ask questions and provide feedback to other groups.
Students working remotely can present their designs as a live presentation during an interactive class meeting, or they can record brief video or multimedia presentations that can be shown during class. If time is limited, student groups could post video or multimedia presentations on a shared server so that students can access and watch the presentations outside of class time. Students can send questions or comments to other groups via e-mail or messaging applications or by commenting on posted videos, and students can respond on the same platform to create a record of the virtual discussion.
After all groups have had the opportunity to present their designs, the class will evaluate the designs to determine which designs best met the criteria and constraints. After the class discussion, student groups should modify their designs to optimize their proposed solutions.
Guide the class as they evaluate their designs by using the following questions.
1. Which structural features were most common among the different designs, and why were those features incorporated by multiple groups into the design solution?
Most designs included interlocking sections in vertical and horizontal seams to act as impact-absorbing structures, like the beetle’s exoskeleton does. These designs used ridged connections shaped like zippers or puzzle pieces between walls of the containers. Those features were used by most groups because they are the key features in the beetle’s exoskeleton that absorb and disperse energy.
2. Which design or designs are the most promising for solving the design problem while meeting all the criteria and constraints?
The class decided that the most promising design solution involved all three of the impact-absorbing features of the beetle’s exoskeleton: the zipperlike connections between the top and bottom half of the exoskeleton, the puzzle-shaped suture that distributes force along its length and the layered tissue and glue structure of the exoskeleton itself. This combination of features should make the container strong but not heavy, and it should not be expensive or difficult to manufacture.
3. As a group, modify your proposed design to improve its capacity to resist crushing. You will use the optimized design to build a prototype to test for durability. Describe the modified design and create a sketch or model of that design. Sketches or models of the design should include information about the prototype’s dimensions, construction and composition.
Sample answer: We are going to prototype a container using several layers of thin cardboard held together by glue. The container’s top half and a bottom half will meet along an edge that fits together with interlocking ridges. The halves of the box will not be made of a continuous piece of cardboard with folds or seams at the corners. Instead, the vertical and horizontal sides of the box will be constructed of separate pieces of the layered cardboard glued together at sutures that are shaped to fit together like interlocking puzzle pieces.
We will use thin cardboard held together with glue, and we will try two prototypes: one with a flexible glue that can bend when force is applied and one with a stiff or rigid glue that can crack when force is applied. We will first make sheets of the layered cardboard material, and then we will cut out the pieces of the container and glue them together using the zipper or puzzle joints along edges or seams to construct a box with a top half and a bottom half that are interlocked. The prototype will be 45 centimeters long by 30 centimeters wide by 30 centimeters deep.
Constructing and testing a prototype
Once groups have finalized their designs, students should construct prototypes to test. Depending on the designs selected by the class, students may need more time to construct prototypes for testing. This can be assigned as homework, or you may need to limit some of the materials or designs students use to ensure a timely completion of the prototypes. After all prototypes have been constructed, groups should test their prototypes for strength and durability.
Understanding how testing will be performed will help students plan and construct testable prototypes. Classroom prototyping and testing are ideal, because students will have access to equipment and materials they may not have at home. The equipment will allow adjustments to be made in real time. If the logistics of constructing and testing prototypes presents too many challenges, you may choose to end the activity after the design phase.
If performing the activity in a remote or virtual setting, teachers may need to construct prototypes or collect prototypes from students prior to testing. If prototypes are to be constructed by students at home but will be tested by the teacher in the classroom, you will have to develop a system by which prototypes can be picked up or delivered after they are constructed.
Teachers can perform the tests as demonstrations from which students make observations and record data. Demonstrations can be livestreamed or can be recorded for later access. If you are testing all the prototypes, you may want to record the tests and have students watch the videos to make observations and take measurements, or you may want to take measurements and construct data tables for students to review and analyze.
If students construct prototypes and perform testing at home, the materials and process may need to be modified to account for available resources. In both the classroom and at home, it is possible to perform testing using simple materials, such as a bathroom scale and objects such as books or fitness weights to provide the compressive force needed to test the prototypes. If students are testing their prototypes independently, you may require them to record the tests so that their group or classmates can verify that the testing procedures were followed by all students and the results can be verified.
Students performing the activity at home will need access to a bathroom scale for testing the amount of mass a box design can support. Students can choose a variety of objects to provide the weight, such as gym weights or weight plates, books, bricks, cinder blocks, rocks, unopened food cans or bottles of water. Students should perform tests that include placing certain amounts of weight on top of the box. Students should record the amount of weight placed on the box and any changes in the shape, dimensions or structure of the box during each trial.
In the classroom, force meters can be used to push on boxes and spring scales can be used to lift boxes to get precise force measurements, but as long as students are conscientious about applying the same amount of force (or weight) during each trial, they don’t necessarily need specific numerical measurements in order to understand how the design(s) performed in the tests. Force meters can give students more options for evaluating how the prototype containers perform when the angle and amount of force are changed.
Remind the students that their groups should address the following four points while constructing and testing their prototypes.
1. Think about how to measure the amount of weight or force a box can withstand. Describe the method you will use to test how well your prototype resists crushing. Identify any measurements you will take or any observations you will record.
Answers will vary. Sample answer: We will test the prototype by placing it in the center of a scale and then placing weights on top of the prototype. We will record each weight and observe any effects on the prototype container. Then we will add more weight to the stack and repeat our observations. We will add weight in 2 kg increments until we reach a total of 25 kg or until the prototype container buckles or fails. We will record how the structure of the container fails and identify which structural features resisted crushing and how.
2. With your group, construct one or more prototypes of your design that you will test using the method you outlined. Note any issues you had or any changes you made to the design while constructing the prototypes.
Answers will vary. Sample answer: It took a long time to make the layered cardboard material and to wait for the glue to set before we could cut out the pieces. We also had trouble making sure the pieces fit together snugly at the seams, and we had to change the shape and size of the box slightly to make the seams fit together.
3. Test your prototype to see how well it resists crushing. Record your observations.
Answers will vary. Students should construct a table that records the amount of force/weight applied to the prototype in each trial step and the observations for that amount of weight. Students should note any changes in the shape or dimensions of the prototype container and the weight the box was supporting when any buckling or deformation occurred.
4. How did your prototype perform? Did it resist crushing, or did the box deform or fail to support the weight?
Answers will vary. Sample answer: Our prototype held up well for most of the weight. The sides of the box started to bow outward when it was supporting 20 kg of weight. The top seams started to rip at the corners when the box was supporting 25 kg.
Analyzing and optimizing a solution
After the prototypes have been tested, student groups should report their results to the class. When students have had the chance to review the test results of other groups, answer the following questions as a class.
1. Which prototype(s) performed the best in the tests? Which performed the worst?
Answers will vary. Sample answer: The prototypes that performed the best, or that best resisted damage caused by stacked weight, were the ones that had reinforced seams that mimicked the puzzle-like sutures located down the center of the beetle’s back. The prototypes that performed the worst were the ones that had 90-degree corners. Containers with slightly trapezoidal shapes, like the body cavity of the diabolical ironclad beetle, better resisted damage.
2. What elements of the successful designs made them more resistant to crushing than the others? Support your answer with evidence and scientific reasoning.
Interlocking seams between the top and bottom of the box and along the vertical edges seemed to resist damage. The interlocking seams probably absorbed and dispersed energy like the seams in the beetle’s exoskeleton do. Layered cardboard materials adhered with flexible glue appeared to resist damage more than the same materials did when adhered with rigid glue. One explanation is that the rigid glue became brittle when it dried, but the flexible glue was able to give a little and disperse the energy from impact. Containers with 90-degree angles for the corners were damaged more easily than the boxes with trapezoidal shapes. I think this is because the non-square angles made it easier for the energy to be dispersed in a different direction.
3. How were the properties of the diabolical ironclad beetle’s exoskeleton expressed in the final container design?
The final container design is not square but is slightly narrower on the bottom and wider at the top, like the shape of the beetle’s exoskeleton. It also included flexible, interlocking connections between the top and bottom halves and puzzle-like sutures in the vertical and horizontal seams that help disperse energy. The final container also included walls made of layers of cardboard held together by a flexible glue.
4. What other properties of a shipping container might engineers want to think about when designing packaging materials that are resistant to crushing forces?
An engineer might want to think more about the shape of the containers to see if another shape, such as a hexagon, might be stronger. They may also want to think about how to make the box lighter or how to make a box that could be stored in less space than the fully constructed prototypes we used. Engineers might also want to think about how to add some internal structural elements like columns to support the top or inserts to hold the product in place so that it does not get damaged by shifting inside the box. Engineers may also want to study how the container structure resists damage when dropped or struck.
5. Based on the outcome of the tests, how would you alter the design of the best-performing prototype to further improve on the strength or durability of your container?
I would like to try additional shapes for the box to see how changing the dimensions of the box alters its strength. I would also like to try changing the way the bottom of the box is constructed to see if the box could be made stronger to prevent sagging when it contains a heavier product.
Potential extensions: Have students test their prototypes to see how much weight the bottom of the container can support when it is filled and lifted, how well the container resists damage when dropped or how well the container resists damage when an object is dropped on it.
C. Wilke. “Analyze This: Insect shells could help builders on Mars.” Science News for Students. November 4, 2020.
Po-Yu Chen. “Diabolical ironclad beetles inspire tougher joints for engineering applications.” Nature. October 21, 2020.
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