Low Velocity Impact on Fibre Reinforced Polymer Composite Laminates

Abstract

A structural component may experience several mechanical loading conditions such as dynamic, cyclic, and static under various environmental conditions. Examples for each loading conditions are as follows: dynamic loading such as impact, cyclic loading such as fatigue, static loadings such as creep and chemical corrosion for environmental condition. These may degrade the material properties with time or may lead to an instantaneous reduction in the strength of the laminates. In both the scenarios, the composite structural material fails catastrophically without any yielding. Any material fails prematurely within the service life of that particular structure than it is a loss of money and time or it may be a matter of life and death of a passenger travelling in an aircraft or an automobile. In order to tackle these problems, it is necessary to understand the FRP laminates behaviour under these situations and environmental conditions. Among various loading conditions, impact is one of the critical loading conditions for FRP composites where the entire impact phenomenon occurs within a short time period. The fracture and damage mechanism involved with the FRP composite materials under impact loading is complicated because of its anisotropic behaviour and heterogeneity. Further, the FRP materials have weak through-thickness properties; thus, these materials become highly vulnerable and susceptible to impact loading, particularly if the impact velocity is low. Because the low velocity impact (LVI) creates barely visible impact damage (BVID) in the structure. This BVID is not visible to the naked eyes and sometimes may go unnoticed during non-destructive inspection. Moreover, the BVID severely reduces the residual strength of the structure and the damage formed in the laminate grows throughout the structure with time leading to sudden catastrophic failure. Thus, this chapter covers various aspects involved with low impact loading condition of FRP composites. Further, different damage detection methods are discussed briefly. The finite element analysis is a power full tool which can be used to understand the complex damage mechanism or failure events associated with FRP composite materials subjected to LVI. These numerical analysis methods use various mathematical models to define the material damage or failure criteria. Moreover, different contact formulations are also used to define the contact between impactor and composite laminate along with the plies interfaces. This chapter provides brief information regarding the common material models and contact formulation used to conduct the finite analysis of FRP composite laminates under LVI.KeywordsFRP compositesLow velocity impactDamage mechanismFinite element analysisMaterial modelsContact definition