The lap shear test sounds as if it measures shear. This video shows that it mostly measures peel! It is one of 9 videos which describe the themes from my book Adhesion Science: Principles and Practice from https://www.destechpub.com/index.php?fuseAction=catalogs.viewItem&catalogID=1&catalogLevelID=&catalogItemID=339. Every principle described in the book is linked to the appropriate app on my Practical Adhesion website: https://www.stevenabbott.co.uk/PracticalAdhesion