Probabilistic strength analysis of four-directional laminated composites

An analytical probabilistic model of multi-step failure of a laminated composite is presented for four-directional reinforcement schemes. From the viewpoint of failure process analysis, the schemes ave considered as fiber-dominated structures. Fiber strength therefore plays a crucial role and the structure is able to resist a loading, even if a composite has been, discontinued. Relationships for reliability prognostication, accounting for random nature of lamina strength properties as well as stress state, are offered and experimentally confirmed for multi-laminated four-directional composites. On the basis of the concept of sublaminates, it is shown that the reliability evaluation may be carried out in the form of two independently solved problems: probabilistic failure analysis of a sublaminate and a sublaminate bundle. Reliability of the sublaminate with a structure [0/+/-Theta/90] is considered in detail and respective numerical results ave presented. Experimental confirmation of the theoretical results is considered for an example of uniaxial tension of a carbon-fiber-reinforced composite with a [0/+/-/45/90](4) structure. (C) 1996 Elsevier Science Limited