An Experimental Study of the Cyclic Compression after Impact Behavior of CFRP Composites

Abstract

The behavior of impact damaged composite laminates under cyclic load is crucial to achieve a damage tolerant design of composite structures. A sufficient residual strength has to be ensured throughout the entire structural service life. In this study, a set of 27 impacted coupon specimens is subjected to quasi-static and cyclic compression load. After long intervals without detectable damage growth, the specimens fail through the sudden lateral propagation of delamination and fiber kink bands within few load cycles. Ultrasonic inspections were used to reveal the damage size after certain cycle intervals. Through continuous dent depth measurements during the cyclic tests, the evolution of the dent visibility was monitored. These measurements revealed a relaxation of the indentation of up to 90% before ultimate failure occurs. Due to the distinct relaxation and the short growth interval before ultimate failure, this study confirms the no-growth design approach as the preferred method to account for the damage tolerance of stiffened, compression-loaded composite laminates.

Adjunctive Damage Model to Describe the Interaction of Different Defect Types in Textile Composites on the Strain-Rate-Dependent Material Behaviour

“…NCF-composites can be compromised by defects that arise during manufacture, like voids [3,4] and fibre misalignments [5][6][7]. However, defects can also occur during product use, such as fatigue [8][9][10] or impact [11][12][13]-induced cracks (further on referred to as service-related defects).…”

Editorial for the Special Issue on Carbon Fiber Composites

“…Preparing these composites (i.e., curing, cyclic compression, cyclic temperature, etc.) is still crucial since processing parameters also play critical roles in determining their final properties [18][19][20][21][22]. The curing reaction progress, which can help to monitor the quality of prepared parts, was measured by Kyriazis et al [23].…”

Analysis Method for Post-Impact Damage Development in Carbon Fiber Reinforced Laminate under Repeated Loading

“…It is well-known, that the presence of impact damage significantly compromises the strength of the composite structural element [3][4][5][6][7][8][9][10][11][12][13]; in particular, the compression strength reduction is pronounced-the so-called compression after impact property (CAI). Contemporary freighters such as MC-21, Boeing-787, Airbus-350, and others contain composite upper wing panels that work under compression loading.…”

“…In this way, residual strength after an impact event during service is incorporated into design requirements and is validated by structural testing. The complexity of the composite structure performance under compression load as well as the phenomenon of the performance reduction of the composite element after impact and the practical necessity to control it through the design of an effective and safe structure explain the research interest in this question [6,7,9,10,12,[14][15][16]. At the same time, a major part of the investigations and developed testing methods are dedicated to the question of static strength, leaving fatigue strength and damage tolerance aspects without a comparable amount of study both on theoretical and experimental levels [17,18].…”