## 3 Experimental Results  
Figure 4 presents, in a double entry array form, an overview of the impact conditions tested on the foam sample. Impact tests with varying negative (anticlockwise) angular velocities and incident angles are reported in the different rows and columns respectively. All the tests were performed at a constant linear velocity of 14 m/s and ambient temperature. Three different spin (0, \(-\)33 and \({}^{\circ}\)66 rev/s) and three different angles (0, 30\({}^{\circ}\) and 60\({}^{\circ}\)) were considered. The top left image corresponds to a normal impact with no spin that has been studied and documented in the previous study [22]. Under the new tested loading conditions, incident and reflected trajectories were easily distinguished. Figure 4: Raw images of the various impact tests performed on the foam sample. Studying the effect of the incident spin for a fixed angle, or the effect of the incident angle for a fixed spin was obtained by focusing on one row or column respectively. For instance, the effect of the incident angle when the ball was thrown at 14 m/s with a backspin of 66 rev/s is presented in Figure 5. Figure 5a displays the raw images of the impact performed on the _foam + compact_ (row 1) and _foam_ (row 2) samples. At first sight, noticeable differences in the reflected trajectories was observed between the two samples for a given \(\{\omega_{\mathrm{i}};\alpha_{\mathrm{i}}\}\). Further quantitative analysis is presented in Figure 5b-d where the linear coefficient of restitution, the spin ratio and the deviation angle are respectively plotted as a function of the incident angle. Increasing the incident angle led to a decrease in the linear coefficient of restitution, the values for the _foam + compact_ being slightly smaller than those measured on the _foam_ alone. Figure 5: (a) Raw images of impact tests performed on the _foam + compact_ and _foam_ samples with varying incident angle (\(\|\vec{\mathrm{V}}_{\mathrm{i}}\|=14\) m/s, \(\mathrm{T}_{\mathrm{amb}}\)). (b) Linear coefficient of Restitution as a function of the incident angle. (c) Spin ratio as a function of the incident angle. (d) Deviation angle as a function of the incident angle. For the two other metrics, a change in the sign was observed between the normal tests (\(\alpha_{i}=0\)) and the tilted ones (\(\alpha_{i}\
eq 0\)). For the normal tests, the spin did not change direction and the ball bounced back with a negative deviation angle. For tilted tests, the spin sign did change leading to negative spin ratio and positive deviation angles. Focusing on the magnitudes, here again a clear distinction could be made between the normal and tilted tests. For normal impacts, the _foam + compact_ sample led to a larger deviation angle and a smaller spin ratio than the _foam_ specimen. The opposite conclusions prevailed when the incident angle was set equal to 30 or 60\({}^{\circ}\). Finally, the greater the incidence, the larger the difference between the two targets. A companion study where the incident angle was prescribed to 30\({}^{\circ}\) and the incident backspin varied, is presented in Figure 6.  
Figure 6: (a) Raw images of impact tests performed on the _foam + compact_ and _foam_ samples with varying angular velocity (\(\vv{V}_{i}\)\(\parallel\) = 14 m/s, T\({}_{\text{amb}}\)). (b) Linear coefficient of Restitution as a function of the incident backspin. (c) Spin ratio as a function of the incident backspin. (d) Deviation angle as a function of the incident backspin. Figure 6a displays the raw images of the impact performed on the _foam_ + _compact_ (row 1) and _foam_ (row 2) samples and Figure 6b-d display respectively the evolution of the linear coefficient of restitution, the spin ratio and the deviation angle as a function of the incident backspin. The linear coefficient of restitution is seen to remain almost constant, with the foam values remaining slightly larger than the foam + compact ones.