Effect of fiber arrangement on residual thermal stress distributions in a unidirectional composite

A three-dimensional finite element analysis is performed to investigate the effects of fiber arrangements on the residual thermal stresses in unidirectional composites of various fiber volume fractions (FVFs). The fiber arrangements include the regular fiber arrays (square and hexagonal arrays) and a random fiber array. Normal, tangential, and shear stresses at the fiber-matrix interface are first obtained using unit cells of the regular square and hexagonal fiber arrays. To simulate better real fiber arrangements, random fiber distribution is modeled and analyzed using a finite element analysis. Statistical distributions of residual thermal stresses are obtained for various FVFs and compared with the results from regular fiber arrays. The effects of constituent material properties of composites on thermal stresses are also taken into consideration. The results indicate that the random arrangement of fibers has a significant influence on residual thermal stresses especially at high FVFs. The mode stresses of the random fibers are well estimated using the square array whereas the mean stresses are better predicted from the hexagonal array. It is shown that predicted coefficients of thermal expansion are not influenced by the microstructure of composites.