Translaminar notch fracture toughness expressions for composite laminates

First, two different test specimens, namely the rectangular tension (RT) and semi-circular bend (SCB) specimens, weakened by U-notches of various notch tip radii and made of E-glass/epoxy composite laminates of different lay-up configurations, are considered for measuring experimentally the translaminar notch fracture toughness (TLNFT) of the composite material under pure mode I loading conditions. Then, two new closed-form expressions are proposed for the TLNFT, by taking advantages of the maximum tangential stress (MTS) and the mean stress (MS) criteria, as well as the recently proposed virtual isotropic material concept (VIMC), with the goal to estimate the experimental results. It is found that both criteria can well estimate the test results that locate always between the predictions of MTS and MS criteria. Taking into account that MTS criterion is more conservative and simpler than MS criterion, it is preferred in mechanical design of notched E-glass/epoxy composite structures.

Automated summary

In this study, two different test specimens, rectangular tension (RT) and semi-circular bend (SCB), weakened by U-notches of different notch tip radii and made of E-glass/epoxy composite laminates with different lay-up configurations, were considered for measuring the translaminar notch fracture toughness (TLNFT) under pure mode I loading conditions. Two new closed-form expressions were proposed for TLNFT estimation based on the maximum tangential stress (MTS) and mean stress (MS) criteria, as well as the virtual isotropic material concept (VIMC). It was found that both criteria provided accurate estimates, with the MTS criterion being preferred for mechanical design of notched E-glass/epoxy composite structures.