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Thanks for the question and sorry for the delay in answering. Generally speaking, measuring the flexural strength gives an indication of a materials resistance to bending under a load. The test methods most often used for plastics are ASTM D790 and ISO 178. Tensile strength is an indication of a materials resistance to being pulled apart. A tensile test generates a stress/strain curve which is used to determine tensile modulus which can provide an indication of how much a material will stretch before it breaks. The test methods most often used for tensile testing of plastics are ASTM D638 and ISO 527. I recognize that these are rather simple explanations but rather that go into a lot of detail here, I suggest that you obtain a good reference book. You will find a book called The Basics of Testing Plastics, edited by Stephen Driscoll, to be an excellent reference guide. It is available from www.astm.org. ASTM Stock #MNL35. Hope this help.