Aim of the present paper is to evaluate how the bearing behavior of pinned flax composites can be influenced by their exposition to critical environment such as marine one. To this scope, flax fibers/epoxy pinned laminate was exposed up to 60 days to salt-fog environment, according to ASTM B 117 standard. In particular, samples having different hole diameter (D), laminate width (W), and hole center to laminate free edge distance (E) have been tested under single lap bearing tests at varying the aging exposition time. Following this procedure, an experimental 2D failure map clustering main failure modes was created by placing the experimental results in the plane E/D versus W/D ratios, and its variation was analyzed at varying the aging exposition. Experimental results showed that environmental aging induced modification on the mechanical performances of the pinned composite. Furthermore, the failure map, defined by E/D and W/D ratios axes, evidenced a progressive modification of damage mechanisms transitions, at increasing the exposition time. In particular, due to significant reductions of tensile and shear strengths of flax laminate, the progressive fracture by bearing mode was not observed for aged samples, replaced by premature and catastrophic shear out and net tension mechanisms.

/pdf/evolution-of-the-bearing-failure-map-of-pinned-flax-5ghpa758cm.pdf

Evolution of the bearing failure map of pinned flax composite laminates aged in marine environment

A simplified predictive approach to assess the mechanical behavior of pinned hybrid composites aged in salt-fog environment

In this study, analytical models considering different material and geometry for ‎both single and double-lap bolted joints were reviewed for better understand how to ‎select the proper model for a particular application. The survey indicades that the ‎analytic models selected for the adhesively single or double bolted lap joints, as well ‎as T, scarf, and stepped joints, with linear material properties are mostly two ‎dimensional and the studies on stress distribution and/or failure of the joint are ‎performed either experimentally, analytically or by finite element method. The results ‎seem to be generally accurate and adequate. Additionally, it was shown that any ‎increase in the bolt-hole clearance leads to an increase in bolt rotation, as well as a ‎decrease in bolt-hole contact area, and hence, a reduction in joint stiffness. Moreover, ‎studies on hybrid joints have revealed that the proper choice of adhesive material in ‎conjunction with bolts or rivets in a joint, allows for significant increase in the static ‎and fatigue strength compared to similar pure bonded joints. Additionally, the results ‎on hybrid scarf joints showed that it is vital to place fasteners closer to the ends of the ‎overlap to suppress the peak peeling stresses and hence, delay the effects of early ‎crack initiation in the adhesive layer...

/pdf/a-review-on-stress-distribution-strength-and-failure-of-4243vkvcmb.pdf

A review on stress distribution, strength and failure of bolted composite joints

A characterization of composite materials of a polyester matrix reinforced with natural fibers of Cuban henequen and organophilized Cuban bentonite was carried out, the experimental results of which are used to formulate, implement, and validate a scalar damage model. The fibers were added on a weight basis of 15, 20, and 25% as a reinforcing material, and organophilized Cuban bentonite, in amounts of 3, 5, and 7% by weight, was added. Samples containing only polymer and fibers showed the best mechanical performance for 25% of fiber, with increases of 51% in the tensile strength and 169% on the impact resistance. Samples containing polymer and clay showed the best results for 5% of bentonite, with increases of 89% in the tensile strength and 83% on the impact resistance, and samples containing 25% fiber and 5% clay were also prepared and achieved a 98% increase in the tensile strength and 219% in the impact strength. The scalar damage model deals with an internal variable, which corresponds to the damage variable, together with a failure surface that allows identifying the mechanical state of the material dependent on the mechanical stress, obtaining an adequate correlation with the results of the experimental tests.

/pdf/mechanical-characterization-of-a-polymer-natural-fibers-1m4oz3ry.pdf

Mechanical Characterization of a Polymer/Natural Fibers/Bentonite Composite Material with Implementation of a Continuous Damage Model


 The use of composite joints has been increased in recent years in structural applications such as aircraft, civil engineering structure, ship structure, wind energy sector, and automotive industry. In this paper, the behaviour of composite bolted connection joints under out of plane loading is investigated. A parametric study was conducted to study the joint stiffness variation with various geometric parameters, which include the edge distance, bolt diameter, plate width, and the laminate stacking sequence. The experimental work was conducted on GFRP tension clips (L-angle) joint specimens manufactured by the vacuum infusion technique. In the present work, two types of laminates were used, unidirectional laminates [0°]5 with an areal density of 1050 gm/m2, triaxial laminates [−45°/+45°/0°]5 with an areal density of 1200 g/m2. A 3D finite element (FE) model was developed to study the effect of joint parameters on its stiffness. Finite element models were constructed, and the experimental results were used to validate the finite element models. The analysis concluded that the failure load increases when the edge distance to bolt diameter ratio (E/D) increases and the triaxial stacking sequence is better than unidirectional. The (E/D) ratio, the (W/D) ratio and stacking sequence were found to be very significant parameters.

Analysis of Composite Bolted Connection Joints Under Out of Plane Loading

Analytical and experimental investigation of Effect of geometric parameters on the failure modes in a single lap single bolted metal to GFRP composite bolted joints subjected to axial tensile loading

The use of composites is increasing in the engineering applications in order to reduce the weight, building energy efficient systems, designing a suitable material according to the requirements of the application. But at the same time, building a structure is possible only by bonding or bolting or combination of them. There are limitations for the bonding methods and problems with the bolting such as stress concentration near the neighborhood of the bolt hole, tensile or shear failure, delamination etc. Hence the design of a composite bolted structure needs a special attention. This paper focuses on the performance of the composite bolted joint under static tensile loading and the effect of variation in the parameters such as the bolt pitch, plate width, thickness, bolt tightening torque, composite material, coefficient of friction between the bolt and plate etc. A simple spring mass model is used to study the single bolted composite bolted joint.The influencing parameters are identified through the developed model and compared with the results from the literature. The best geometric parameters for the applied load are identified for the composite bolted joints.

https://iopscience.iop.org/article/10.1088/1757-899X/225/1/012215/pdf

Parametric Study of Single Bolted Composite Bolted Joint Subjected to Static Tensile Loading

Investigative studies on the mechanical behavior of Jute, Sisal, Hemp, and glass fiber-based composite material

Design and development of agricultural spraying system

Composite bolted joints are preferred connection in the composite structures to facilitate the dismantling for the replacements/ maintenance work. The joint behavior under tractive forces has been studied in order to understand the safety of the structure designed. The main objective of this paper is to investigate the behavior of single-lap joints in carbon fiber reinforced epoxy composites under traction loading conditions. The experiments were designed to identify the effect of bolt diameter, stacking sequence and loading rate on the properties of the joint. The experimental results show that the parameters influence the joint performance significantly.

L.V. Awadhani

Papers

Analytical and experimental investigation of Effect of geometric parameters on the failure modes in a single lap single bolted metal to GFRP composite bolted joints subjected to axial tensile loading

Parametric Study of Single Bolted Composite Bolted Joint Subjected to Static Tensile Loading

Investigative studies on the mechanical behavior of Jute, Sisal, Hemp, and glass fiber-based composite material

Design and development of agricultural spraying system

Behavior of single lap composite bolted joint under traction loading: Experimental investigation