Cold Temperature Effects on Consistent and Architecturally Hybridized Woven Kevlar/Epoxy Laminates

Abstract

The primary objectives of the present experimental research were to characterize and compare the interlaminar mode-I fracture toughness, crack growth and flexural stiffness behaviors of Kevlar KM2-Plus® fiber/epoxy matrix laminates constructed of various woven fabric architectures including plain, 2 × 2 twill and 4H satin weaves at cold [− 46 °C (− 50 °F)] and room [20 °C (68 °F)] temperatures. Secondary objectives were to evaluate and compare the fracture and flexure behaviors for two types of woven laminate constructions referred to as consistent and hybridized laminates. Consistent laminates were constructed with a single fabric weave style throughout all plies and were representative of laminate configurations used in traditional composites design. The hybridized laminates incorporated a mixture of different ply weave styles arranged in a strategic manner to achieve functionally-graded attributes and performance benefits such as enhanced damage tolerance, load carrying capacities, residual strengths and dynamic energy absorption/dissipation levels. The experimental results demonstrated that the interlaminar mode-I critical strain energy release rates, GIc and flexure moduli, Eflex were temperature dependent and that the hybridized laminate provided the optimal combination of highest fracture toughness and bending stiffness with the least sensitivity to temperature. The concept of hybridized laminate architectures can be used to mitigate temperature effects on fracture and flexural stiffness in addition to increasing damage tolerance, load carrying capacities, flexure stiffness, fracture toughness, residual strengths and dynamic energy absorption/dissipation.