## 5 Conclusions  
In this study, quasi-static and dynamic compressive experiments of UHMWPE laminate in the out-of-plane and in-plane directions were performed. The stress-strain relationship, the influence of different thickness, area, and shape, and the maximum stress and fracture stress were studied. The material showed a dependency on strain rate and loading direction. FE models with cohesive elements were developed. The biggest relative errors between numerical and experimental maximum stress for the out-of-plane and in-plane directions were 7.3% and 3.4%, respectively. The numerical failure form showed good agreement with the experimental form in both directions. The detailed features for different directions are concluded below. 1. For both directions, the stress-strain curves had a self-installation zone and under-loading zone. In the out-of-plane dynamic tests, the loading zone of the stress-strain curve could be divided into a non-linear period and linear period. In the in-plane dynamic tests, the loading zone of the stress-strain curve could be divided into a linear period and non-linear period. 2. In the out-of-plane dynamic tests, the maximum stress increased with the increasing strain rate until fracture occurred under a certain strain rate. In contrast, in the in-plane dynamic tests, the fracture happened at every tested strain rate. For both directions, the fracture stress increased with the increasing strain rate. The fracture stress of the out-of-plane dynamic tests was relatively higher than the fracture stress of the in-plane dynamic tests. In both the out-of-plane and the in-plane directions, the slope and fracture stress of the dynamic stress-strain curves were higher than the slope and fracture stress of the quasi-static stress-strain curves. 3. In the out-of-plane dynamic tests and simulation, the thickness did not have a clear influence on the modulus. In the in-plane dynamic tests and simulation, the thinner specimen had a smaller modulus. 4. In the out-of-plane dynamic simulation, a larger gap between sub-laminates caused the slope of the non-linear period of stress-strain curves to be shallower and longer; however, a larger gap \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Size of Specimen** & **Pressure** & **Impact Velocity** & **Strain Rate** & **Fracture Stress** \\
**mm** & **MPa** & **m/s** & **s\({}^{-1}\)** & **MPa** \\
**L-W-ls** & & & **Exp/Sim/RE** & **Exp/Sim/RE** \\ \hline \(8\times 8\times 8\) & 0.2 & 15.03 & 1813.6\%/1872.0\%/3.2\% & 35.1\%/36.3\%/3.4\% \\ \(8\times 8\times 8\) & 0.3 & 17.35 & 2146.8\%/2159.0\%/0.6\% & 37.0\%/37.9\%/2.4\% \\ \(8\times 8\times 8\) & 0.4 & 18.73 & 2310.0\%/2333.6\%/1.0\% & 38.0\%/38.6\%/1.6\% \\ \(4\times 8\times 8\) & 0.2 & 15.03 & 1822.5\%/1876.0\%/2.9\% & 33.4\%/32.2\%/3.6\% \\ \(8\times 8\times 5\) & 0.2 & 15.03 & 2855.7\%/2984.0\%/4.5\% & 35.7\%/34.7\%/2.8\% \\ \hline \hline \end{tabular}
\end{table} 
Table 11: The experiment/simulation/relative errors of strain rate and fracture stress. Figure 49: The experimental and simulated first-derivative curves of different specimens under same impact velocity: (**a**) effect of strain rate (\(8\times 8\times 8\)); (**b**) effect of different size. did not clearly influence the slope of the linear period and the maximum stress. This indicates that the non-linear period was mainly caused by the compactness of the specimen. 5. In the out-of-plane direction, both simulation and experiment results showed that many small fragments were squeezed out of the specimen in the damaged situation. In the in-plane direction both simulation and experiment showed that the specimens were squeezed to become big pieces. All authors contributed to the work. [PERSON] designed and conducted the experiments, established the numerical models, and performed the data analysis. [PERSON], [PERSON], and [PERSON] helped to conduct the experiments. [PERSON] and [PERSON] guided the research work. [PERSON] and [PERSON] edited/proofread the paper. All authors have read and agreed to the published version of the manuscript.