Preliminary Study of the Behavior of Composite Material Box Beams Subjected to Impact

LS-DYNA 940.2 was used to study the response of composite box beams subjected to oblique (or inclined) impacts by a rigid cylinder. The square cross-section composite beams were 1000 mm long with 50 mm by 50 mm nominal cross-sectional dimensions. The rigid cylinder had a 50 mm diameter and a 100 mm length and impacted the box beam on the top panel. The composite box beam and the cylinder were modeled with 3 mm thick Belytschko- Tsay shell elements. Material 54: MAT_ENHANCED_COMPOSITE_DAMAGE was used to model the orthotropic composite material used in the sidewalls of the box beam. In order to simulate an experimentally observed progressive “tearing” failure in the box beams during the impact events, spotwelds were used to model the corners of the beams (i.e. the joints between the four sides of the box beam). Spotweld failure parameters were calculated from the transverse tensile and in-plane shear strengths of the composite material. The benchmark analysis used for the study was one in which the rigid cylinder hit the beam at an incident angle of 25° to the horizontal axis at a velocity of 2 m/s. The coefficient of friction between the cylinder and the beam was 0.1. The results of the benchmark analysis were compared to results of analyses with various angles of impact, impact velocities, and coefficients of friction. Results were compared with respect to the displacement path of the cylinder, the angle of the path of the cylinder with respect to the horizontal direction (rebound angle), the change in velocity of the cylinder, and the resultant impact force on the cylinder. In general, the rebound angle and velocity of the cylinder appeared to have a rational dependence on the incident angle, the coefficient of friction, and the initial velocity.