A high-throughput technique to evaluate the probability distribution of strength of adhesively bonded joints after moisture absorption

The reliability of adhesive bond strength influences the applicability
of structural adhesives in industries. The statistical probability
distribution of the strength of adhesive joints is an
essential indicator when designing and choosing adhesives. In
this study, we experimentally studied the probability distribution
of the strength of adhesive joints. The strength data were collected
using a novel high-throughput technique consisting of
a sample preparation method and shear testing device.
Numerous cylindrical butt shear-joint specimens were prepared
by mechanical machining and tested using a self-developed
shear testing device. The effect of moisture absorption by the
adhesive was specifically considered. The probability distribution
of the shear strength of the epoxy adhesive joints was characterized
using five probability distribution functions: Normal,
Lognormal, Exponential, Weibull, and Gamma. Quantile – quantile
plots were employed to determine the suitability of each
distribution function. The results suggested that the Weibull
and Normal distributions were best suited for describing the
probability distribution of the strength of the epoxy adhesive
joints. The Weibull distribution is particularly suitable for brittle
epoxy adhesives. Moisture absorption reduced both the mean
and variance of the shear strength, which might be attributed to
the plasticization of the adhesives. The high-throughput method
proposed in this study significantly improved the efficiency of
testing adhesive joints. It not only contributes to the study of the
strength distributions of adhesive joints but also helps to shorten
the research and development cycle of new adhesives by facilitating
rapid strength evaluation.