Validation of fracture envelopes of structural adhesives for mixed-mode strength prediction of bonded joints

In the design of adhesive structures, it is extremely important to accurately predict their strength and fracture properties (critical strain energy release rate in tension, GIC, and shear, GIIC). In most cases, the loads occur in mixed-mode (tension plus shear). Thus, it is of great importance the perception of fracture in these conditions, namely of the strain energy release rates in tension, GI, and shear, GII, relative to different crack propagation criteria or fracture envelopes. This comparison allows to determine the most suitable energetic propagation criterion to be used in cohesive zone models (CZM). The main objective of this work is to verify, by CZM, which is the power parameter (?) that best suits the energetic crack propagation criterion for CZM modelling, using single-lap joints (SLJ) and double-lap joints (DLJ) with aluminium adherends and bonded with three different adhesives. With this purpose, numerical simulations of the SLJ and DLJ are carried out, and the maximum load (Pm) is compared with experiments. For the Araldite AV138 and Araldite鮮 2015, the energetic criterion resulting from the experimental work provided matching numerical results and, thus, the fracture envelopes were validated. The Sikaforce� 7752 results were slightly offset due to CZM law shape issues

Fracture modelling of adhesively-bonded joints by an inverse method

Nowadays, any structure must have strength, robustness and lightness, which has increased the industrial interest and research efforts in adhesive joining, mainly in the improvement of strength and fracture properties of adhesives. Thus, in recent years, the use of adhesive joints in industrial applications has gradually grown, replacing some traditional bonding methods, since they have advantages such as reduced stress concentrations, reduced weight and cost, and ease of processing/manufacturing. In this work, the cohesive laws of three adhesives, Araldite AV138, Araldite鮮 2015 and Sikaforce� 7752, were obtained by the application of an inverse adjustment method between the numerical and experimental load-displacement curves (P-?) of Double-Cantilever Beam (DCB) tests for tensile characterization and End-Notched Flexure (ENF) tests for shear characterization. Next, these laws were validated with experimental data of single-lap joints (SLJ) and double-lap joints (DLJ), using Abaqus�. For the Araldite� AV138 and Araldite� 2015, in tension and shear, the triangular law accurately predicted the behaviour of the SLJ and DLJ. For the Sikaforce� 7752, the triangular law did not suitably fit the experimental results. Due to its ductility, the Sikaforce� 7752 could be modelled with a trapezoidal law for improved accuracy

Efficacy and safety of combined piroxicam, dexamethasone, orphenadrine, and cyanocobalamin treatment in mandibular molar surgery

Third molar extraction is a common procedure frequently accompanied by moderate or severe pain, and involves sufficient numbers of patients to make studies relatively easy to perform. The aim of the present study was to determine the efficacy and safety of the therapeutic combination of 10 mg piroxicam, 1 mg dexamethasone, 35 mg orphenadrine citrate, and 2.5 mg cyanocobalamin (Rheumazin®) when compared with 20 mg piroxicam alone (Feldene®) in mandibular third molar surgery. Eighty patients scheduled for removal of the third molar were included in this randomized and double-blind study. They received (vo) Rheumazin or Feldene 30 min after tooth extraction and once daily for 4 consecutive days. Pain was determined by a visual analogue scale and by the need for escape analgesia (paracetamol). Facial swelling was evaluated with a measuring tape and adverse effects and patient satisfaction were recorded. There was no statistically significant difference in facial swelling between Rheumazin and Feldene (control group). Both drugs were equally effective in the control of pain, with Rheumazin displaying less adverse effects than Feldene. Therefore, Rheumazin appears to provide a better risk/benefit ratio in the mandibular molar surgery. Since the side effects resulting from nonsteroidal anti-inflammatory drug administration are a severe limitation to the routine use of these drugs in clinical practice, our results suggest that Rheumazin can be a good choice for third molar removal treatment