**Author details**

**Figure 11.** Four UT images for medium energy (20 J) impacted NCF laminate. Each image reports the internal structure

**Figure 12.** Four UT images for high energy (40 J) impacted NCF laminate. Each image reports the internal structure of

internal damage. The analysis of the UT images shows that: (i) the impact damage develops differently at interfaces between layers characterised by diverse fibre orientations; (ii) the delamination area increases with rising distance (depth) from the impact surface as well as with growing impact energy and (iii) the delamination outline exhibits the well-known hatshaped configuration [20]. The UT analysis also reveals the absence of delamination in a small

In low-velocity impacted composite materials, damages due to this type of loading usually develop inside the material structure and are difficult to detect. Delamination, arising from dynamic loading, is seemingly the most investigated impact failure mode due to its high criticality. However, other damage types such as matrix cracking, fibre-matrix debonding and fibre breakage can also occur due to impact loads. These damage mechanisms can interact with each other and lead to considerable reduction of the load-carrying capability of composite structures. Thus, the thorough material damage characterisation is essential to assess the impact damage criticality. This chapter focussed on the non-destructive characterisation and assessment of low-velocity impact damage in composite material laminates through ultrasonic testing and inspection. A general description of low-velocity impact damage generation in composite materials was presented. Ultrasonic testing methodologies for composite

of 1 mm thickness from upper (a) to lower laminate surface (d).

62 Characterizations of Some Composite Materials

1 mm thickness from upper (a) to lower laminate surface (d).

zone directly below the impact surface contact point.

**5. Conclusions**

Tiziana Segreto1,2\*, Roberto Teti1,3 and Valentina Lopresto3

\*Address all correspondence to: tsegreto@unina.it

1 Fraunhofer Joint Laboratory of Excellence on Advanced Production Technology (Fh-J\_LEAPT UniNaples), Naples, Italy

2 Department of Industrial Engineering, University of Naples Federico II, Naples, Italy

3 Department of Chemical, Materials and Industrial Production Engineering, University of Naples Federico II, Naples, Italy
