There are 4 main types of tests necessary to determine the strength of a composite.
Tensile strength
Compression
Shear
Fatigue
Tensile strength
Tensile strength is a materials ability to resist tearing due to tension. To test a materials tensile strength it is placed in a tensile testing system and pulled on until the material is stretched too much to go back to it original shape. The zone of which a material is able to perform its best is within the yield strength of the material (shown in the graph below).
This graph represents the average stress-stain curve for materials. In order to choose a material, something with a high yield strength is best, as it is the force a material can withstand without deformation. Strain hardening is when a material is the strengthening of a metal or polymer by plastic deformation. Work hardening may be desirable, undesirable, or inconsequential, depending on the context. Strain hardening may be useful but for making a car it seems like it would be difficult to make a material and stretch it to the desired size and shape.
How to test tensile strength?
To perform tensile testing a, universal test machine frame, load cell, controller and/or indicator, and proper grips and fixturing to hold the sample are required.
The universal machine frame is the structure needed to pull the material apart. It provides rigid support.
Load cells measure the amount of force applied to the sample.
A controller indicator controls how the frame behaves during testing. I.E how fast and how much force is applied to the material being tested.
Grips are required to hold the material during testing. These change based on the material being tested.
https://fractory.com/ultimate-tensile-strength/
https://interestingengineering.com/understanding-tensile-strength-its-importance-in-engineering
https://www.admet.com/testing-applications/test-types/tension-testing/
Compression strength
Compressive strength is a materials ability to resist deforming or breaking under compression.
How is compressive strength tested?
Compression tests are typically done by applying pressure to a material using flat platforms. This test is usually done on a block of material rather than a sheet. During the test, various properties of the material are calculated and plotted as a stress strain diagram which is used to determine qualities such as elastic limit, proportional limit, yield point, yield strength, and, for some materials, compressive strength.
https://www.instron.us/en-us/our-company/library/test-types/compression-test
https://www.mee-inc.com/hamm/tension-and-compression-testing/
Shear strength
The shear strength of a material is its ability to resist forces that cause the material's internal structure to
slide against itself (shown in the picture to the left).
How to test shear strength?
hmmmmmmmm
https://matmatch.com/learn/property/shear-strength
https://www.corrosionpedia.com/definition/1026/shear-strength
Material Fatigue
Material fatigue is a phenomenon where structures fail when they are subjected to a repetitive force or load. Material Fatigue occurs even when the force or stress exerted on the material is much less then the material’s static strength. Fatigue is the most common source of failures when it comes to mechanical structures.
How to test Material Fatigue
To test material fatigue, tests such as the tensile test, compression test, and shear test are done for long periods of time with less force. The force applied typically resembles the frequency of a sin wave.