Mechanics of woven roving/ mat laminate failure in a quasi-static tensile test

Abstract

Based on tensile tests of non-standard specimens with large dimensions, an attempt was made to explain the mechanics of failure of woven roving/mat laminates with different numbers of layers. The need to use non-standard specimens in tests resulted from the impossibility of interpreting the processes taking place in tensile specimens in specimens with standard dimensions, the results of which are published in the scientific literature. In the tensile tests, four loading phases were observed, in which in the last two the structure of matrix was failed by micro- and macro-cracks, and finally by delamination through the laminates. To describe the fracture mechanics of the discussed laminates, the principle of energy equivalence was used in the transformation of elastic strain energy into binding energy. Although the processes of laminate destruction occur in the matrix, depending on the number of layers, it was found that two different processes of destruction of the internal structure with three variants of elastic strain energy distribution lead to the final delamination of the laminates. The use of energy to describe the failure of laminates in the third phase of specimen loading leads to the definition of such concepts as the dominance of failure stresses and the dominance of failure strains in the process of cracking the laminate structure. Experimental studies indicate a gradient distribution of binding energy towards the center of unloaded specimens, assumed on the basis of a literature review.