This paper is a review of low-velocity impact responses of composite materials. First the term ‘low-velocity impact’ is defined and major impact-induced damage modes are described from onset of damage through to final failure. Then, the effects of the composite's constituents on impact properties are discussed and post-impact performance is assessed in terms of residual strength.

Review of low-velocity impact properties of composite materials

Current and future potential applications for three-dimensional (3D) fibre reinforced polymer composites made by the textile processes of weaving, braiding, stitching and knitting are reviewed. 3D textile composites have a vast range of properties that are superior to traditional 2D laminates, however to date these properties have not been exploited for many applications. The scientific, technical and economic issues impeding the more widespread use of 3D textile composites are identified. Structures that have been made to demonstrate the possible uses of 3D composites are described, and these include applications in aircraft, marine craft, automobiles, civil infrastructure and medical prosthesis.

Review of applications for advanced three-dimensional fibre textile composites

A concerted survey is presented of the existing theories for predicting the strength and modulus of particulate-filled polymeric composites. The macroscopic behaviour of particulate composites is affected by the size, shape, and the distribution of the inclusions. The interfacial adhesion between the matrix and inclusion is also important. The limitation of theoretical models in describing these parameters and expressing the experimental data on the macroscopic behaviour is demonstrated.

A review of particulate reinforcement theories for polymer composites

A review of the investigations that have been made on adhesively bonded joints of fibre-reinforced plastic (FRP) composite structures (single skin and sandwich construction) is presented. The effects of surface preparation, joint configuration, adhesive properties, and environmental factors on the joint behaviour are described briefly for adhesively bonded FRP composite structures. The analytical and numerical methods of stress analysis required before failure prediction are discussed. The numerical approaches cover both linear and non-linear models. Several methods that have been used to predict failure in bonded joints are described. There is no general agreement about the method that should be used to predict failure since the failure strength and modes are different according to the various bonding methods and parameters, but progressive damage models are quite promising since important aspects of the joint behaviour can be modelled by using this approach. However, a lack of reliable failure criteria ...

https://journals.sagepub.com/doi/pdf/10.1243/14644207JMDA219

Adhesively bonded joints in composite materials: An overview

In the present paper, the following topics are reviewed in detail: (a) the available adhesives, as well as their recent advances, (b) thermodynamic factors affecting the surface pretreatments including adhesion theories, wettability, surface energy, (c) bonding mechanisms in the adhesive joints, (d) surface pretreatment methods for the adhesively bonded joints, and as well as their recent advances, and (e) combined effects of surface pretreatments and environmental conditions on the joint durability and performance. Surface pretreatment is, perhaps, the most important process step governing the quality of an adhesively bonded joint. An adhesive is defined as a polymeric substance with viscoelastic behavior, capable of holding adherends together by surface attachment to produce a joint with a high shear strength. Adhesive bonding is the most suitable method of joining both for metallic and non-metallic structures where strength, stiffness and fatigue life must be maximized at a minimum weight. Polymeric adhesives may be used to join a large variety of materials combinations including metal-metal, metal-plastic, metal-composite, composite-composite, plastic-plastic, metal-ceramic systems. Wetting and adhesion are also studied in some detail in the present paper since the successful surface pretreatments of the adherends for the short- and long-term durability and performance of the adhesive joints mostly depend on these factors. Wetting of the adherends by the adhesive is critical to the formation of secondary bonds in the adsorption theory. It has been theoretically verified that for complete wetting (i.e., for a contact angle θ equal to zero), the surface energy of the adhesive must be lower than the surface energy of the adherend. Therefore, the primary objective of a surface pretreatment is to increase the surface energy of the adherend as much as possible. The influence of surface pretreatment and aging conditions on the short- and long-term strength of adhesive bonds should be taken into account for durability design. Some form of substrate pretreatment is always necessary to achieve a satisfactory level of long-term bond strength. In order to improve the performance of adhesive bonds, the adherends surfaces (i.e., metallic or non-metallic) are generally pretretead using the (a) physical, (b) mechanical, (c) chemical, (d) photochemical, (e) thermal, or (e) plasma method. Almost all pretreatment methods do bring some degree of change in surface roughness but mechanical surface pretreatment such as grit-blasting is usually considered as one of the most effective methods to control the desired level of surface roughness and joint strength. Moreover, the overall effect of mechanical surface treatment is not limited to the removal of contamination or to an increase in surface area. This also relates to changes in the surface chemistry of adherends and to inherent drawbacks of surface roughness, such as void formations and reduced wetting. Suitable surface pretreatment increases the bond strength by altering the substrate surface in a number of ways including (a) increasing surface tension by producing a surface free from contaminants (i.e., surface contamination may cause insufficient wetting by the adhesive in the liquid state for the creating of a durable bond) or removal of the weak cohesion layer or of the pollution present at the surface, (b) increasing surface roughness on changing surface chemistry and producing of a macro/microscopically rough surface, (c) production of a fresh stable oxide layer, and (d) introducing suitable chemical composition of the oxide, and (e) introduction of new or an increased number of chemical functions. All these parameters can contribute to an improvement of the wettability and/or of the adhesive properties of the surface.

Adhesively-bonded joints and repairs in metallic alloys, polymers and composite materials: Adhesives, adhesion theories and surface pretreatment

Our predictive model for particulate filled composite materials is applied to epoxy resin toughened by rubber spheres. Good agreement is found between predicted values of stiffness and experimental measurements. The variability of yield stress with volume fraction is explained. The observed fracture processes, including rubber cavitation, are explored; the importance of thermal stresses is highlighted. The fracture behaviour of these materials is discussed in the light of these predictions.

A predictive model for particulate-filled composite materials

The effect of delamination geometry on the compressive failure of composite laminates

The detection of damage in composite laminates is a vital step in allowing their wider use in critical applications. Measurement of specific damping capacity (SDC) is a useful potential method for damage detection. The work reported in this paper consists of measurements and analysis of SDC of composite beams in flexure. Beams have been tested before and after the introduction of damage using quasi-static loading or fatigue. The damage mechanisms and location of the damage in the woven laminates is deduced from comparison of dynamic results with the dynamic response from the cross-ply laminates containing well characterized damage. The results indicate that measurement of SDC is a promising technique for detection of initial damage in woven fabric composites.

FJ Guild

Papers

A predictive model for particulate-filled composite materials

The effect of delamination geometry on the compressive failure of composite laminates

Vibration damping for crack detection in composite laminates

Microstructural image analysis applied to fibre composite materials: a review

Finite element prediction of damping of composite GFRP and CFRP laminates – a hybrid formulation – vibration damping experiments and Rayleigh damping