Back of Napkin Math
If a vacuum bag pulls 14.7 psi over 100 square inches, the total force applied is about this many pounds.
What is ~1470 pounds?
This thermoset resin family is widely used in composites due to its good mechanical properties and relatively easy processing.
What is epoxy?
These two brothers built the first successful powered airplane in 1903.
Who are the Wright brothers?
This property measures a material’s resistance to deformation under load.
What is stiffness?
The Acronym “KISS” stands for this.
What is Keep it Simple Stupid?
A simply supported beam is 12 ft long with a 600-lb point load at the center. The maximum bending moment occurs at midspan. This is the bending moment at midspan in lb-ft.
What is 1,800 lb-ft?
During thermoset curing, the point where resin stops flowing and becomes a continuous network is called this stage.
What is gelation?
This aerospace company produced the first widely used carbon fiber aircraft structures on the 787.
What is Boeing?
Materials like wood and composites that behave differently depending on direction are described by this term.
What is anisotropic?
This term completes the phrase, “There is nothing more permanent than a _______”
What is a “temporary solution/fix”?
A tool heats from 70°F to 270°F and has a CTE of 12 µin/in-°F over 20 inches. The expansion is roughly this many thousandths of an inch.
What is ~0.048 in (48 thou)?
This temperature marks the transition where a polymer changes from glassy and rigid to rubbery.
What is glass transition temperature (Tg)?
This engineer developed the famous equation relating stress, strain, and modulus.
Who is Robert Hooke?
This ratio compares stress to strain in the elastic region of a material.
What is Young’s modulus?
When a malfunctioning machine or system works after being hit or smacked, we say it was fixed using this technique.
What is “percussive maintenance”?
A laminate with 60% fiber volume and fiber modulus of 230 GPa with matrix modulus of 3 GPa has an approximate longitudinal modulus of this value using the rule of mixtures.
What is ~139 GPa?
These resins cure via addition reactions and release no byproducts, making them common in aerospace epoxies.
What are addition-cure resins?
This Scottish engineer improved the steam engine and helped launch the Industrial Revolution.
Who is James Watt?
This ratio describes how much a material contracts laterally when stretched longitudinally.
What is Poisson’s ratio?
The Acronym “RUD” stands for this.
What is “Rapid Unscheduled Disassembly”?
A 5 lb resin mix requires a 100:27 resin-to-hardener ratio by weight. The hardener needed is approximately this many pounds.
What is ~1.06 lb?
This chemical group reacts with epoxide rings in many aerospace epoxy curing systems.
What are amines?
This inventor pioneered Bakelite, the first fully synthetic plastic.
Who is Leo Baekeland?
This property measures resistance to crack growth and catastrophic fracture.
What is fracture toughness?
This term describes forgetting to plug in a device, creating the ultimate barrier to current flow.
What is “High Impedance Air Gap”?