The lap shear test is a method used to evaluate the adhesive strength between two overlapping materials. In this test, two substrates are bonded together with an adhesive and then pulled apart in a shear direction. The force required to break the bond is measured, providing valuable data on the adhesive's performance. This test is commonly used in industries such as aerospace, automotive, and construction to ensure that adhesives meet specific strength requirements. The results help engineers select appropriate adhesives for various applications, ensuring safety and reliability in the final product.